ENGINEERS: December 2005

Sunday, December 25, 2005

AFTER BPO IT’S EPO’S

" title="Atom Few years ago, It was call centers that were outsourced to India, then came the technical and animation outsourcing phase. This year there has been a rapid growth in the new form of outsourcing- education process outsourcing (EPO) or online tutoring.
INDIAN brains are recognized world over. Today teachers in India are tutoring children across the globe in maths and science, thanks to the internet. With the rapid development in technology and other online learning, tutoring companies have got a boost. Many are investing in technologies like multimedia chat rooms, voice over internet protocol and so on. The real power of internet as an educational medium is not in its ability to cheaply broadcast canned messages to the masses, but in its ability to network students and teachers together.
HOW DOSE EPO WORKS?
Students across the globe and Indian teacher log on to a website at a predefined time for a particular course. The technology used is IEC, which integrates web, video and voice in an IP based software platform. While it is a one on one session for a student, the teacher usually attends to multiple students simultaneously on different links. The session is generally of an hour duration, providing sufficient time to even ask questions.feed">Site Feed

What is FlashGet?

" title="Atom feed">Site FeedFlashGet is specifically designed to address two of the biggest problems when downloading files: Speed and management of downloaded files.If you've ever waited forever for your files to download from a slow connection, or been cut off midway through a download - or just can't keep track of your ever-growing downloads - FlashGet is for you. FlashGet can split downloaded files into sections, downloading each section simultaneously, for an increase in downloading speed from 100% to 500%. This, coupled with FlashGet's powerful and easy-to-use management features, helps you take control of your downloads like never before.
SpeedFlashGet can automatically split files into sections or splits, and download each split simultaneously. Multiple connections are opened to each file, and the result is the the most efficient exploitation of the bandwidth available. Whatever your connection, FlashGet makes sure all of the bandwidth is utilized. Difficult, slow downloads that normally take ages are handled with ease. Download times are drastically reduced.ManagementFlashGet is capable of creating unlimited numbers of categories for your files. Download jobs can be placed in specifically-named categories for quick and easy access. The powerful and easy-to-use management features in FlashGet help you take control of your downloads easily.
HighlightsSpeed. The ability to split files into up to 10 parts, with each part downloading simultaneously. Up to 8 different simultaneous download jobs. FlashGet just might be the fastest download software around! Organize. Categorize files with FlashGet's integrated & simple-yet-powerful file management features before your files engulf you! Mirror search. Automatically search for the fastest server available for the fastest possible downloads. Automatically have FlashGet dial up, hang up & shut down the computer when you're not around! Schedule to download files whenever you feel! Whether it's while you snooze or during off-peak periods, certain times each weekday, weekend or whatever. The choice is yours! Manage your copious downloaded files with FlashGet's simple yet powerful user interface. Automate your FlashGet downloads with a browser click! Supports Internet Explorer, Netscape and Opera* web browsers. *with freely downloadable plug-in.Superior ease-of-use. FlashGet's interface is logical, integrated, informative and customizable.Queue your downloads with FlashGet's logical queueing system. Control the download speed limit so that downloading files doesn't interfere with your web browsing!Easily see any aspect of your downloads at a glance. Whether it be server status messages, monitoring splits, amount downloaded, time left...whatever! No excessive clicking into multiple open windows to see what's going on! Customize the the FlashGet toolbar and user interface, including the Graph and log window colors. Support for proxy servers for maximum downloading flexibility. Speak your language with FlashGet's auto-select language capabilities (20+ selectable languages available). Check for FlashGet updates from within FlashGet. Monitor your download progress, server status messages and download splits graphically with the easiest, most functional user interface around!
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Surface mounted optics aid automated assembly

Surface mounted optics aid automated assembly

Michael Hatcher reports on a technique developed by a Swiss collaboration that paves the way towards faster, automated assembly of miniature optical subsystems.
From Opto & Laser Europe

Miniature mounts

Although optical subsystems are widespread in applications such as sensing and telecoms today, the way in which the optics components are assembled and packaged remains a tricky and time-consuming business. For the most part, optics are passively aligned and then stuck together with glue.
In high-volume semiconductor manufacture, such techniques would be unthinkable. More sophisticated methods for the assembly of photonics modules are essential if their manufacture is to reach the same level of automation as that of electronics while maintaining high-precision alignment and high reliability.
A collaboration between the Swiss Federal Institute of Technology in Lausanne (EPFL) and Leica Geosystems of Switzerland has recently developed a technique that appears to offer a way forward. The group's three-dimensional miniaturized optical surface-mounted devices (TRIMO-SMD) imitate the assembly techniques that were developed for the electronics industry 20 years ago. The method, which uses six-axis robotic motion, automated optical alignment and laser-reflow soldering to make photonics modules, is currently being made commercially available by Leica Geosystems.
Automated assembly
Opto & Laser Europe reported on the first generation of this automated assembly equipment back in September 1998. Originally developed by the EPFL, optical surface-mounted devices (O-SMD) were useful for assembling optics of approximately 8-10 mm in size. A spin-off company called BrightPower was set up to commercialize the technology.

Lidar transceiver

However, the O-SMD technique, which involves simultaneous laser-welding of three metal cups that act as a tripod holding the optical component, was judged to be unsuitable for micro-optical assembly. For the past few years, Leica Geosystems has been working closely with both the Institute of Applied Optics and the Institute of Robotics at EPFL on a technique that, while it works on a similar principle to O-SMD, is suitable for use in manufacturing micro-optic systems - TRIMO-SMD.
"We decided that O-SMD was way too large for future projects," said Laurent Stauffer, who has been managing the technological development of the first commercial product to use TRIMO-SMD at Leica Geosystems. "TRIMO works extremely well with laser diodes. In many applications where you have a laser diode and you need an optical component you can use TRIMO, so there is a very wide potential market."
TRIMO-SMD is designed for use with optical components of around 2 mm in diameter. "We regard the high throughput and reliability possible with TRIMO-SMD to be something of a quantum step in optical assembly," Stauffer told Opto & Laser Europe.
Smaller optics
Laser-welding a mount to a substrate was not viable for making subsystems that incorporate smaller optics. Instead, laser-soldering or brazing was found to be the best method of attachment. This is the key difference between O-SMD and TRIMO-SMD: rather than holding the optics in place with a tripod of metal cups, the optical element in TRIMO-SMD is suspended up to 400µm away from the substrate material, and is moved into position by a robot. There is no contact between the substrate and the optical mount, which according to Stauffer is an improvement on O-SMD. "Contact between the substrate and the element was a bit of a problem in the past," he said.
In TRIMO-SMD, a mount called a universal holder is produced first. This holder consists of a 2.5mm-diameter round cup and two vertical arms 2.6mm long. It is covered with a tin preform in preparation for the soldering process. "The universal holder is our standard interface between the optics and the ground plate," explained Stauffer. A sub-mount containing the optical element is then laser-welded to the holder. With the holder gripped by a robot-controlled jig, the optical element is aligned using cameras and sensors. The robot can move in six dimensions and, according to Stauffer, has a placement precision of 0.25µm.
When the optical element is suspended precisely above the desired position, an 808nm continuous-wave high-power diode laser fires 20-40W through the substrate underneath the optics. The substrate is partially transparent and part-metallized to enable wetting of the surface during soldering. When the laser hits the preform, the tin melts and then drops onto the mounting plate to form a stable joint with the holder.
This method fixes the optical element into position in just 2s. The soldering causes slight thermal shrinkage that alters the exact position of the optical element. Stauffer says, however, that this can be easily resolved: "With a 200µm gap, there is typically a shrinkage of 3µm - this can be calibrated accurately, and you can simply offset the optical element before soldering," he commented. After soldering, the gripper is relaxed and the optics left in a fixed position. "The placement of each optic is repeatable to within 1µm [to a 99% confidence limit]," said Stauffer.

TRIMO-SMD robot

When Leica Geosystems and EPFL first developed TRIMO-SMD, they had a particular product in mind: a laser rangefinder used in military applications. Leica needed to place a beam-shaping optic directly in front of a laser diode inside the rangefinder. Thanks to the new micro-optic assembly produced using TRIMO-SMD, the distance over which the equipment is effective has been increased from 5 to 10km.
Award-winning technology
The technique had a welcome boost in February this year, when its selection as one of the winners of the Swiss Technology Award meant that it was exhibited at the Hannover Messe technology show. "We found five very interested potential customers for TRIMO-SMD at Hannover," Stauffer said. A spin-off company dedicated to the commercialization of TRIMO-SMD is planned and will be set up in the autumn of this year. According to Stauffer, "Leica will support the company over the first few years and the goal is to offer a manufacturing service, technical support and consulting."
In the meantime, Leica is looking to cash in on its investment (the company owns two patents protecting the technology) by licensing the technique to industrial partners. "We think that there is a very wide market for TRIMO-SMD, particularly companies that are involved in optical sensing and telecommunications," Stauffer said. "Leica Geosystems will use TRIMO for applications using optical sensing and we expect other customers to do the same. Medical applications are also possible."
In addition to the laser rangefinder, Leica has built a lidar transceiver module using TRIMO-SMD. The technique enabled a dramatic reduction in the size and weight of the transceiver and improved its stability and robustness. Coupled with a drop in price, the module could open up a new market for transceivers.
A third module that has been built by Leica using TRIMO-SMD is a series of components that produce second-harmonic generation from an Nd:YAG microchip laser. "All of the devices used are ideally sized for TRIMO-SMD, and components like the self-focusing lens can be positioned to a very high accuracy," said Stauffer.
He recommends that anybody considering using the TRIMO technique should carefully plan exactly what they need to assemble: "You need to 'think TRIMO', and design your optics accordingly." He adds that although micro-optic assembly currently takes around 10-15 min using the technique (the active alignment has been only partially automated), this could be shortened and optimized for high-throughput mass-production by any company willing to invest in the technology.
If a major manufacturer of optical subsystems is forthcoming with that kind of investment, the TRIMO-SMD technique could propel photonics manufacturing along the same path as electronic

Friday, December 23, 2005

iTunes

" title="Atom feed">Site FYou can use iTunes to create your own personal digital music library and easily organize and listen to your collection of digital music files. You can also create your own custom audio CDs and transfer your music to an Apple iPod.

Important: After installing iTunes 4.6 for Windows, you'll only be able to transfer music to your iPod using iTunes. To transfer music from MusicMatch Jukebox or Audible Manager to your iPod, you'll need to first import the music into iTunes. For more information, search iTunes and Music Store Help.

System requirements
iTunes 4.6 requires Windows 2000 or Windows XP with a QuickTime-compatible audio card. Also make sure you have the latest Service Pack for your computer using Windows Update.

To create CDs or DVDs, you need an iTunes-compatible CD or DVD burner. To use the iTunes visualizer, you need a QuickTime-compatible video card.

If you plan to listen to music previews or buy music from the iTunes Music Store, a DSL, cable modem, or local area network (LAN) Internet connection is recommended.

Installing iTunes 4.6
Double-click the iTunes 4.6 installer and follow the instructions that appear. When you install iTunes, QuickTime 6.5.1 is also installed.

What's new in iTunes 4.6
iTunes 4.6 includes support for playing your music wirelessly using AirPort Express with AirTunes. It also includes a number of other minor enhancements.

For more information
For more information about using iTunes, open iTunes and choose Help > iTunes and Music Store Help. Type a question in the search field, or click Overview or Contents. If you're connected to the Internet, you can learn how to use iTunes by taking the iTunes tutorial. Visit www.apple.com/support/itunes/windows/tutorial/index.html.

If you've purchased music from the Music Store and have a billing question, open iTunes and choose Help > Music Store Customer Service.

For more information about using your iPod with iTunes, open iTunes and choose Help > iPod Help.

For the latest news about iTunes, visit the iTunes website at www.apple.com/itunes or the Apple Support website at www.apple.com/support/itunes. For the latest information about iPod, visit www.apple.com/ipod.

A note about copyright
This software may be used to reproduce materials. It is licensed to you only for reproduction of non-copyrighted materials, materials in which you own the copyright, or materials you are authorized or legally permitted to reproduce. If you are uncertain about your right to copy any material, contact your legal advisor.eed

Researchers compile radiation database

" title="AtoAs the number of photonic systems used in nuclear, space and high-energy physics environments grows, radiation-induced performance-degradation of optical materials and devices becomes an increasingly important issue. Johan van der Linden discovers how it is to be tackled.
From Opto & Laser Europe
Testbed reactor
Late last year, lasers were used for the first time to transmit data between orbiting satellites. But as the photonics revolution begins to extend into the harsh environments of the space and nuclear industries, there is an urgent need to assess the performance of optical components - both active and passive - under the influence of various forms of radiation.
One organization that aims to do this is the Belgian nuclear research centre SCK-CEN. During the past decade it has investigated the radiation resistance of a number of photonic components, including optical fibres, semiconductor light sources and photodetectors, fibre-optic couplers and sensors, and liquid-crystal cells.
Comparable effects
Francis Berghmans, head of photonics at SCK-CEN, has led the work on the effects of radiation. "We found that, although the basic environmental conditions such as dose rate, total dose and radiation type may differ from one application to the next, the fundamental effects that influence devices often remain comparable," he said.
However, the results of exposure can vary. Exposure to particle radiation, such as proton and neutron beams, can cause displacement damage, whereas exposure to electromagnetic radiation, such as gamma rays, will primarily induce defects resulting from ionization. This means that even though a particular component may be able to withstand large doses of gamma radiation, making it useful in civil nuclear facilities, it could be too sensitive to protons to be suitable for space applications.
Lanzarote
Passive devices, particularly optical fibres comprising Bragg gratings, are the most frequently studied components, due to their potential use as strain, temperature and multi-point structural integrity sensors in thermonuclear environments.
High radiation doses generally create defects - known as colour centres - in optical glasses, which can lead to significant transmission losses and light generation from unwanted wavelength bands. This is a major obstacle to the efficient operation of optical communication systems.
Berghmans has found that in standard germanium-doped fibres, high radiation doses can induce absorption losses of several hundred dB/km in the 1310 nm and 1550 nm telecom transmission windows. Pure silica fibres suffer about one tenth of the losses seen in germanium-doped fibres. However, the optical fibres required for data transmission in nuclear facilities are comparatively short in length, so standard fibre loss levels may be acceptable.
In semiconductor-based active optical components, radiation-induced damage can introduce defect states into the crystal lattice and create new energy levels in the bandgap. These defects may act as generation-recombination centres, leading to increased threshold current and lower optical output from laser diodes. In photodiodes, increased dark current and lower responsivity are the likely hazards.
VCSEL array
"Our experiments have demonstrated that photodetectors are the most critical components in optical communication systems," said Berghmans. His findings show that, at low doses, III-V-based photodiodes are not as sensitive to radiation-induced degradation as silicon-based detectors. As far as sources are concerned, vertical-cavity surface-emitting lasers (VCSELs) seem to have more radiation tolerance than edge-emitting light sources. Berghmans puts this enhanced tolerance down to the VCSEL's thin active layer and initially brief carrier lifetime, which mean that a great many defects must be induced before they seriously affect the efficiency of the device.
Optical components are increasingly used in space applications, ranging from teleobjective lenses to communication systems for use in spacecraft and between satellites.
Most commonly-applied optical materials are prone to darkening - or solarization - in irradiation environments, so glass manufacturers supply radiation-hardened products (analogues of standard glasses that have been doped with cerium oxide) which exhibit improved end-of-life transmission properties. However, the performance of spaceborne optical systems rests on the reliability of refractive components.
Cerium doping retains more than 90% transmittance in the visible spectrum, but it has been shown to have some negative effects on other system performance parameters. For instance, radiation has a substantial effect on the refractive-index profile of cerium-doped components.
Glass sample a)
Last November, the ESA's Research and Technology Centre (ESTEC) in Noordwijk, the Netherlands, presented the results of a study it had assigned to the France-based space company Astrium and SCK-CEN to assess the stability of physical properties in commercially available glass materials.
Dominic Doyle, a technical officer at ESTEC, explained the need for such a study: "The main reason was the deficit of a reliable, usable and easily accessible database concerning the radiation characteristics of refractive optical materials. This [study] is a step towards establishing a comprehensive database to quantify radiation effects for use in the design and development of spaceborne optical systems."
Glass sample b)
Michel Fruit, manager of optical design and engineering at Astrium, and his colleagues place special emphasis on studying refractive index changes in proton and gamma radiation fields to simulate a range of different Earth orbits. "We found that cerium-doped specimens can show significant steps in the wavefront profile," he said.
Depending on the base material, the refractive index change can be positive as well as negative, although it is generally rather small (less than 10-5). In optical systems that use a large number of lenses, however, the effect can be significant. Fortunately, says Fruit, it can be predicted. "The radiation-induced refractive index change and absorption-increase sensitivity is linear - particularly in proton environments - and this allows a dose-coefficient modelling approach to be used," he said.
Huge task lies ahead
Compiling the database is an enormous task and it will be several years before it is accessible, probably via the ESA's Web site. Once complete, the database could be of use in a range of related fields such as deep-ultraviolet lithography and pulsed high-power lasers, because such systems need high-performance refractive optical components.
Since gamma rays are photons, any optical system that is exposed to high-energy photons could benefit from the radiation studies. This applies to deep-ultraviolet lithography in particular, since it would use many optical components and the long exposure times involved would result in significant radiation doses. Because such systems work to tight tolerances, an awareness of possible radiation effects is crucial.
According to Doyle, standard methods must now be adopted. "Given the workload involved [in compiling the database], one of our most immediate goals is to concentrate on the standardization of the assessment methodology with industrial, institutional and agency partners," he said. "Such a methodology could eventually be approved by the ISO or the European Cooperation for Space Standardization."
m feed">Site Feed

Pulse Spreading

" title="Atom feeThe data which is carried in an optical fibre consists of pulses of light energy following each other rapidly. There is a limit to the highest frequency, i.e. how many pulses per second which can be sent into a fibre and be expected to emerge intact at the other end. This is because of a phenomenon known as pulse spreading which limits the "Bandwidth" of the fibre.

Figure 11 Pulse Spreading in an Optical Fibre
The pulse sets off down the fibre with an nice square wave shape. As it travels along the fibre it gradually gets wider and the peak intensity decreases.
Cause of Pulse Spreading
The cause of cause spreading is dispersion. This means that some components of the pulse of light travel at different rates along the fibre. there are two forms of dispersion.
1. Chromatic dispersion
2. Modal dispersion
Chromatic Dispersion
Chromatic dispersion is the variation of refractive index with the wavelength (or the frequency) of the light. Another way of saying this is that each wavelength of light travels through the same material at its own particular speed which is different from that of other wavelengths.
For example, when white light passes through a prism some wavelengths of light bend more because their refractive index is higher, i.e. they travel slower This is what gives us the "Spectrum" of white light. The "red' and "orange" light travel slowest and so are bent most while the "violet" and "blue" travel fastest and so are bent less. All the other colours lie in between.
This means that different wavelengths travelling through an optical fibre also travel at different speeds. This phenomenon is called "Chromatic Dispersion".
Figure 10 Dispersion of Light through a Prism
Modal Dispersion
In an optical fibre there is another type of dispersion called "Multimode Dispersion".
More oblique rays (lower order modes) travel a shorter distance. These correspond to rays travelling almost parallel to the centre line of the fibre and reach the end of fibre sooner. The more zig-zag rays (higher order modes) take a longer route as they pass along the fibre and so reach the end of the fibre later.
Now:-
Total dispersion = chromatic dispersion + multimode dispersion
Or put simply: for various reasons some components of a pulse of light travelling along an optical fibre move faster and other components move slower. So, a pulse which starts off as a narrow burst of light gets wider because some components race ahead while other components lag behind, rather like the runners in a marathon race.
Consequences of pulse spreading
Frequency Limit (Bandwidth)
The further the pulse travels in the fibre the worse the spreading gets

Figure 12 - Merging of Pulses in a Fibre.
Pulse spreading limits the maximum frequency of signal which can be sent along a fibre. If signal pulses follow each other too fast then by the time they reach the end fibre they will have merged together and become indistinguishable. This is unaceptable for digital systems which depend on the precise sequence of pulses as a code for information. The Bandwidth is the highest number of pulses per second, that can be carried by the fibre without loss of information due to pulse spreading.
Distance Limit
A given length of fibre, as explained above has a maximum frequency (bandwidth) which can be sent along it. If we want to increase the bandwidth for the same type of fibre we can achieve this by decreasing the length of the fibre. Another way of saying this is that for a given data rate there is a maximum distance which the data can be sent.
Bandwidth Distance Product (BDP)
We can combine the two ideas above into a single term called the bandwidth distance product (BDP). It is the bandwidth of a fibre multiplied by the length of the fibre. The BDP is the bandwidth of a kilometre of fibre and is a constant for any particular type of fibre. For example, suppose a particular type of multimode fibre has a BDP of 20 MHz.km, then:-
1 km of the fibre would have a bandwidth of 20 MHz
2 km of the fibre would have a bandwidth of 10 MHz
5 km of the fibre would have a bandwidth of 4 MHz
4 km of the fibre would have a bandwidth of 5 MHz
10 km of the fibre would have a bandwidth of 2 MHz
20 km of the fibre would have a bandwidth of 1 MHz
The typical B.D.P. of the three types of fibres are as follows:-
Multimode 6 - 25 MHz.km
Single Mode 500 - 1500 MHz.km
Graded Index 100 - 1000 MHZ.km
NB: The units of BDP are MHz.km (read as megahertz kilometres). They are not MHz/km (read as megahertz per kilometres). This is because the quantity is a product (of bandwidth and distance) and not a ratio.
Choice of Fibre
Multimode Fibre
Muitimode fibre is suitable for local area networks (LAN's) because it can carry enough energy to support all the subscribers to the network. In a LAN the distances involved, however, are small. Little pulse spreading can take place and so the effects of dispersion are unimportant.
Single Mode Fibre.
Multimode Dispersion is eliminated by using Single Mode fibre. The core is so narrow that only one mode can travel. So the amount of pulse spreading in a single mode fibre is greatly reduced from that of a multimode fibre. Chromatic dispersion however remains even in a single mode fibre. Thus even in single mode fibre pulse spreading can occur. But chromatic dispersion can be reduced by careful design of the chemical composition of the glass.
The energy carried by a single mode fibre, however, is much less than that carried by a multimode fibre. For this reason single mode fibre is made from extremely low loss, very pure, glass.
Single mode low absorption fibre is ideal for telecommunications because pulse spreading is small.
Graded Index Fibre
In graded index fibre rays of light follow sinusoidal paths. This means that low order modes, i.e. oblique rays, stay close to the centre of the fibre, high order modes spend more time near the edge of core. Low order modes travel in the high index part of the core and so travel slowly, whereas high order modes spend
predominantly more time in the low index part of the core and so travel faster. This way, although the paths are different lengths, all the modes travel the length of the fibre in tandem, i.e., they all reach the end of the fibre at the same time. This eliminates multimode dispersion and reduces pulse spreading.
Graded Index fibre has the advantage that it can carry the same amount of energy as multimode fibre. The disadvantage is that this effect takes place at only one wavelength, so the light source has to be a laser diode which has a narrow linewidth.
Figure 13 - Ray Paths in Graded Index Fibred">Site Feed

High Precision Attenuating Optical Fiber Streamlines Fixed In-Line Attenuator Production

LASER 2003: Can fibre lasers steal the show?

" title="Atom feed">Site FeedAccording to many in the laser industry, fibre lasers are now a serious alternative to solid-state and carbon dioxide lasers for industrial material-processing applications. Here, we look at some of the fibre-laser vendors that will be looking to make a splash at this year's event.
From LASER. World of Photonics Visitor Magazine
Fibre preform
The boom years of optical telecoms may be long gone, but some of the technological advances of that time will be on view to LASER 2003. World of Photonics visitors in some unexpected ways.
One example of these is in the field of high-power fibre lasers, which are sure to turn a few heads in the production-engineering sector. During the telecoms boom, firms needed reliable, high-power 980 nm diode sources to pump erbium-doped fibre amplifiers (EDFAs). The technology was developed rapidly to satisfy the market's demand.
With components like EDFAs no longer so popular, these diodes are being employed in high-power fibre lasers that are finding industrial applications such as in the manufacture of car parts and medical devices.
Two show exhibitors in particular - Southampton Photonics (SPI) of the UK and IPG Photonics, US - have shifted their emphasis away from telecoms to the industrial applications of high-power fibre lasers.
On the fast track
IPG was first out of the blocks with its high-power sources and is seeing them used in the automotive and medical-device industries. "The telecoms hiccup has allowed us to fast-track high-power fibre lasers," said Bill Shiner, business-development manager of IPG Photonics' industrial-laser group.
While IPG has dived straight into the market, SPI has added to its ranks senior staff with experience in the industrial sector. The firm's plan is to sell its fibre sources to OEMs, rather than direct to the user application. SPI has developed what it believes to be a superior fibre design. So far, it has focused on military applications (it has contracts with DARPA in the US and Qinetiq in the UK), but at LASER 2003. World of Photonics, SPI will be launching its first fibre-laser products tailored to the industrial market.
In a fibre laser, a doped silica fibre is excited by a diode source. Two Bragg gratings written into the fibre act like the mirrors of a "normal" laser cavity to generate the laser emission, resulting in a compact source with excellent beam quality. IPG has found a way to "bundle" its ytterbium-doped fibre lasers together efficiently, and it has produced systems that emit up to 6kW continuous-wave power at 1080nm.
Aside from the many technical advantages claimed by the makers of fibre lasers, it is their cost-of-ownership that may turn out to be the key factor. Stuart Woods is SPI's director of business development. He estimates that over the typical lifetime of a source, the total cost of ownership of a fibre laser is approximately one-third that of a similar carbon dioxide or solid-state device. This is despite the initial purchase of a fibre laser generally being slightly more expensive than a DPSS laser, and it highlights the exceptionally low maintenance cost. Woods has another way of putting it: the fibre laser gives the lowest "cost per millijoule" of any comparable laser, coming in at less than $200.
Faster welding
IPG recently installed a 2kW fibre laser at the Edison Welding Institute, a leading materials-joining organization in the US, and a 6kW fibre-laser unit at an (undisclosed) automotive plant in Germany. During trials, the air-cooled 6kW unit was integrated with a robot and used for welding and cutting steel and aluminium alloys. According to IPG, the fibre laser could cut and weld faster than comparable YAG sources.
"Last year industry experts forecast that a multiyear development would be required to convince automotive and other major industries to accept this unknown technology," said Shiner, adding: "Large numbers of prospective customers are now lining up for pre-production tests."
Shiner is confident that IPG lasers will go on to make a big impact on a variety of applications: "The lasers have a 20% wallplug efficiency and are ideal for marking, cutting and welding," he said. "I believe that they will revolutionize the industrial-laser market."
Meanwhile, several SPI units are undergoing customer-evaluation tests. SPI's DARPA project is to build a singlemode, single-polarization 1kW fibre laser with an M2 value of 1. The first phase of this project is now complete, with the firm producing a 50W polarization-maintained (PM) output at 1060nm and a 25W non-PM output at 1550nm. The Qinetiq contract is to produce distributed-feedback fibre lasers for acoustic sensor arrays, and the first stage of this project was completed in December last year.
SPI's fibre lasers are based on its patented fibre design. Mikhail Zervas, SPI's chief scientist, explained: "Conventional active fibres are core-doped at the centre of the fibre. Our design is based on ring doping." Zervas says that conventional doping increases saturation and limits the maximum extractable energy from the fibre. With ring doping, the gain is more controlled and the output less noisy.
With its Q-switched fibre lasers, SPI reckons that it should be able to deliver more energy per pulse than is possible with the conventional active fibre architecture.
JDS Uniphase also has plans for its fibre lasers. Product marketing manager Rüdiger Hack says that the firm is working to increase the power output: "The next step is 50 and 100W models with an M2 of 1."
While Hack also believes that fibre lasers will revolutionize industrial-laser applications, he believes that costs are currently too high: "Manufacturers need to work on driving down component and manufacturing costs, especially for high-volume applications."
Shiner's view appears to dispute this: he says that the price of IPG's fibre sources are comparable with those of Nd:YAG sources up to around the 4kW mark. Any higher, and he admits that fibre lasers do become the more expensive option.
Not that this is dulling his optimism: "I think [fibre lasers] will become huge in the cutting market. I don't really see how we can lose - in a few years they should really dominate the YAG business, especially in areas like automotive welding. We will take on YAGs first and then carbon dioxide lasers."
Currently, the market - estimated to be worth $60-70 m - is dominated by IPG, which has a share of more than 50%. JDS Uniphase takes the only other significant share with 26%. This looks set to change as SPI enters the market, with other major laser vendors also expected to get in on the act.
Woods' estimate is that the total addressable market for fibre lasers could be as much as $300 m. He argues that multisource agreements between fibre-laser vendors could be the way forward.
Well, so much for the hype. At LASER 2003. World of Photonics you can see what the fibre-laser vendors have on offer.

Innovative optics targets next-generation telecoms

" title="Atom feed">Site FeedDespite the telecoms downturn there is still plenty of innovation emerging from the R&D labs. Steve Ferguson of Marconi Communications examines 10 optical technologies.
Best of both
There has been plenty of bad news in the telecoms industry over the last two years, but if you take a long-term view then telecoms has been a resounding success. Revenues of telecoms operators have risen enormously over the last 150 years, the amount of traffic per bearer has increased steadily and analysts forecast that the market for "next-generation optical products" is healthy.
Equipment vendors and network operators that want to take advantage of the long-term potential of the industry must now watch the innovation going on in research labs in order to see which optical technologies will be key for future growth.
In the near future, industry emphasis will continue to be on consolidation and cost reduction and many products will be based on existing components and product types. However, looking beyond 2005, there are a variety of emerging technologies that could well prove invaluable to this industry.
Enhance and advance
Much of the research currently under way builds on techniques and ideas that already exist and combines them to create dramatically better systems. Wavelength switching and broadband passive optical networks are key examples.
Wavelength switching can be used to reroute traffic, independently of payload protocol. Remotely reconfigurable optical add-drop multiplexers (R-OADMs) provide the first stage of wavelength switching, and Marconi has already deployed more than 300 R-OADMs in public networks, each capable of supporting up to 32 x 10 Gbit/s.
Before full photonic cross-connects, which promise massive savings in cost, space and power consumption, can be deployed, traffic needs to grow. Current 32-, 40- and 80-channel systems still have light traffic loads.
With greater loads, many operators and vendors view R-OADMs as a significant feature of future networks. Wavelength switching will offer the greatest value when combined in nodes with electronic switching, under a single level of automated management control.
Broadband passive optical networks (B-PONs) are an attractive way to deliver fibre-to-the-home (FTTH). Although the major investments in B-PONs in the mid-1990s were too early to impact the market, investors have recently begun to show increased interest again.
Japan leads the way in FTTH deployment and authorities predict more than 7 million users there by 2006. This is in part because of Japan's high density of housing, but also owing to a national policy for broadband. Some European countries, such as Italy and Germany, are also deploying FTTH in areas such as greenfield housing.
One application that could also drive FTTH deployments is the provision of video services, which several operators have earmarked as their best bet for good future margins. While asymmetric digital subscriber line systems combined with MPEG4 coding could deliver video services, there are many constraints. Delivery across fibre removes these.
Electronic integration
The use of electronics to improve the performance of photonic systems is another major research area, and the technology is now moving beyond 10 Gbit/s. One example application is enabling multimode fibre (which offers low installation costs but is often thought to be limited in terms of speed or distance) to achieve 10 Gbit/s in B-PON or access network applications that require a range of around 1 km. Techniques that could help this include forward error correction and fibre compensation.
Forward error correction (FEC) improves photonic-performance margins by digitally correcting errors after they occur but before the data are used. The fast response of electronics, compared with today's typical photonic devices, is an advantage when compensating for polarization-mode dispersion. FEC uses powerful processing electronics for 10 Gbit/s systems and is being developed further for use at 40 Gbit/s. In addition, true digital photonics techniques could give 160 Gbit/s.
Fibre compensation is a precursor to the true integration of electronic and photonic technologies on the same chip. This technique compensates for fibre impairments at the photonic level to prevent digital errors before they occur. The technique is similar to that of the phone-line modem in a PC, but 200,000 times faster.
Many fibre routes need conditioning for use beyond 2.5 Gbit/s owing to the effects of dispersion. The effects of current photonic-compensation techniques are marginal for 40 Gbit/s and introduce a 20-30% loss. Electronic compensation is not as effective as true photonic compensation, but its costs are much lower.
Digital boost
Although still at the research stage, digital photonics techniques such as multiwavelength regenerators, multiple integrated photonic digital devices and optical packet switching could greatly improve system capacity, cost and functionality.
Holey fibre
Multiwavelength regenerators promise to remove the planning burden of analogue characterization for long-distance routes. Two approaches are being studied at present. The first employs multiple regenerators in a chip, which is difficult to do and is really just putting more electronics in a package. A more innovative approach is the regeneration of multiple (about 10) wave-division multiplexing (WDM) channels within one optical-processing device, typically a variant of a semiconductor optical amplifier. Such devices could be deployed in around three to five years.
Multiple integrated photonic digital devices (devices integrated onto one substrate and suitable for mass production) could be used to create devices for FEC, demultiplexing and more intriguing applications such as encryption. Photonics researchers want to be ready for the day when substrates other than silicon will be used.
As is the case with many photonics applications that burst onto the market, distributed switching and control have been the focus of much research in universities. However, improvements in all-optical switching and optical memories are still needed, and optical packet switching will probably first appear as optically assisted packet switching in single-router nodes.
Holey structures
Photonic-crystal devices and fibres rely on photonic bandgaps and promise impressive control over the properties of optical devices.
Just as electronic bandgaps are the basis of transistors and integrated circuits, photonic bandgaps could form the basis of many types of active and passive optical devices. A photonic crystal is a lattice in a dielectric material created, for example, by an array of holes in an optical waveguide. These holey structures can be tailored to create photonic bandgaps - a range of frequencies in which electromagnetic waves cannot propagate.
Optical technologies
On a substrate such as silicon, a pattern of microscopic holes or similar discontinuities shapes the light field, enabling overall device sizes just a fraction of those today. For example, 3 dB fibre couplers now on the market are tens of millimetres long. In a photonic-crystal device, the equivalent functionality could fit into just 20 µm.
Most work at present is on 2D devices - structures patterned in two directions and constant in the third. Fabricated via photolithography, plasma etching and metallization, such structures can produce nearly lossless filters, waveguides and mirrors, lasers with a low current threshold and holey optical fibres (see below).
Three-dimensional devices are just starting to emerge. These are much harder to create, but will be needed to make active photonic-bandgap-based devices. Scientists in Japan plan to build commercial 3D optical crystals in space, relying on the zero gravity to prevent distortions in the lattice.
Photonic crystals offer the possibility of single-substrate integration of photonics and electronics. When combined with digital photonics, this could enable the multiple parallel processing of ultrahigh-speed signals.
Photonic-crystal fibre is the most commercialized photonic-crystal technology, and comprises a long thread of silica glass with a periodic array of holes (containing vacuum, air or liquid) running along its length. It can give extreme properties, such as selective forbidden regions of wavelengths or high nonlinearity. Other fibre designs can offer greatly reduced signal degradation for transport applications, nonlinearity 100 times lower than current fibres and almost perfect control of chromatic dispersion.
In the longer term, the attenuation could potentially be much lower than on legacy fibre. The industry is not there yet, however - current loss from photonic-crystal fibre is 13 dB/km compared with legacy-fibre loss of 0.2 dB/km - and there are big questions regarding what to do about splices.
Data storage
The final category of emerging technologies is a wild card - optical signal storage. Researchers in this field have come up with many ideas but, so far, few useful techniques. For example, there is still no optical random-access memory. Such a device could revolutionize router design because optical memory is potentially much faster, although it would not necessarily be smaller or denser than electronics.
There is considerable ongoing research in this area. Light has already been slowed by 2000 times in a solid-state device and the latest results show that it can be slowed at room temperature. This could prove a crucial breakthrough. After all, laser development only began seriously once the first room-temperature lasers appeared.
Commercial potential
All of the above technologies could prove highly useful in tomorrow's optical networks. Photonics is inherently as powerful as electronics, and the potential of the emerging combination of the two is awesome. There are plenty of areas for innovation, as is evident at the key industry conferences and meetings. Positioning these ideas for commercial success is a real challenge but, crucially, the long-term market in telecoms is still healthy.

THE BASICS OF FIBER OPTIC CABLE

" title="Atom feed">Site THE BASICS OF FIBER OPTIC CABLE

BRIEF OVER VIEW OF FIBER OPTIC CABLE ADVANTAGES OVER COPPER:
• SPEED: Fiber optic networks operate at high speeds - up into the gigabits• BANDWIDTH: large carrying capacity• DISTANCE: Signals can be transmitted further without needing to be "refreshed" or strengthened.• RESISTANCE: Greater resistance to electromagnetic noise such as radios, motors or other nearby cables.• MAINTENANCE: Fiber optic cables costs much less to maintain.
In recent years it has become apparent that fiber-optics are steadily replacing copper wire as an appropriate means of communication signal transmission. They span the long distances between local phone systems as well as providing the backbone for many network systems. Other system users include cable television services, university campuses, office buildings, industrial plants, and electric utility companies.
A fiber-optic system is similar to the copper wire system that fiber-optics is replacing. The difference is that fiber-optics use light pulses to transmit information down fiber lines instead of using electronic pulses to transmit information down copper lines. Looking at the components in a fiber-optic chain will give a better understanding of how the system works in conjunction with wire based systems.
At one end of the system is a transmitter. This is the place of origin for information coming on to fiber-optic lines. The transmitter accepts coded electronic pulse information coming from copper wire. It then processes and translates that information into equivalently coded light pulses. A light-emitting diode (LED) or an injection-laser diode (ILD) can be used for generating the light pulses. Using a lens, the light pulses are funneled into the fiber-optic medium where they transmit themselves down the line.
Think of a fiber cable in terms of very long cardboard roll (from the inside roll of paper towel) that is coated with a mirror.If you shine a flashlight in one you can see light at the far end - even if bent the roll around a corner.
Light pulses move easily down the fiber-optic line because of a principle known as total internal reflection. "This principle of total internal reflection states that when the angle of incidence exceeds a critical value, light cannot get out of the glass; instead, the light bounces back in. When this principle is applied to the construction of the fiber-optic strand, it is possible to transmit information down fiber lines in the form of light pulses.
There are three types of fiber optic cable commonly used: single mode, multimode and plastic optical fiber (POF).Transparent glass or plastic fibers which allow light to be guided from one end to the other with minimal loss.
Fiber optic cable functions as a "light guide," guiding the light introduced at one end of the cable through to the other end. The light source can either be a light-emitting diode (LED)) or a laser.
The light source is pulsed on and off, and a light-sensitive receiver on the other end of the cable converts the pulses back into the digital ones and zeros of the original signal.
Even laser light shining through a fiber optic cable is subject to loss of strength, primarily through dispersion and scattering of the light, within the cable itself. The faster the laser fluctuates, the greater the risk of dispersion. Light strengtheners, called repeaters, may be necessary to refresh the signal in certain applications.
While fiber optic cable itself has become cheaper over time - a equivalent length of copper cable cost less per foot but not in capacity. Fiber optic cable connectors and the equipment needed to install them are still more expensive than their copper counterparts.
Single Mode cable is a single stand of glass fiber with a diameter of 8.3 to 10 microns that has one mode of transmission. Single Mode Fiber with a relatively narrow diameter, through which only one mode will propagate typically 1310 or 1550nm. Carries higher bandwidth than multimode fiber, but requires a light source with a narrow spectral width. Synonyms mono-mode optical fiber, single-mode fiber, single-mode optical waveguide, uni-mode fiber.
Single-mode fiber gives you a higher transmission rate and up to 50 times more distance than multimode, but it also costs more. Single-mode fiber has a much smaller core than multimode. The small core and single light-wave virtually eliminate any distortion that could result from overlapping light pulses, providing the least signal attenuation and the highest transmission speeds of any fiber cable type. Single-mode optical fiber is an optical fiber in which only the lowest order bound mode can propagate at the wavelength of interest typically 1300 to 1320nm.
jump to single mode fiber page

Multimode cable is made of of glass fibers, with a common diameters in the 50-to-100 micron range for the light carry component (the most common size is 62.5). POF is a newer plastic-based cable which promises performance similar to glass cable on very short runs, but at a lower cost.
Multimode fiber gives you high bandwidth at high speeds over medium distances. Light waves are dispersed into numerous paths, or modes, as they travel through the cable's core typically 850 or 1300nm. Typical multimode fiber core diameters are 50, 62.5, and 100 micrometers. However, in long cable runs (greater than 3000 feet [914.4 ml), multiple paths of light can cause signal distortion at the receiving end, resulting in an unclear and incomplete data transmission.
The use of fiber-optics was generally not available until 1970 when Corning Glass Works was able to produce a fiber with a loss of 20 dB/km. It was recognized that optical fiber would be feasible for telecommunication transmission only if glass could be developed so pure that attenuation would be 20dB/km or less. That is, 1% of the light would remain after traveling 1 km. Today's optical fiber attenuation ranges from 0.5dB/km to 1000dB/km depending on the optical fiber used. Attenuation limits are based on intended application.
The applications of optical fiber communications have increased at a rapid rate, since the first commercial installation of a fiber-optic system in 1977. Telephone companies began early on, replacing their old copper wire systems with optical fiber lines. Today's telephone companies use optical fiber throughout their system as the backbone architecture and as the long-distance connection between city phone systems.
Cable television companies have also began integrating fiber-optics into their cable systems. The trunk lines that connect central offices have generally been replaced with optical fiber. Some providers have begun experimenting with fiber to the curb using a fiber/coaxial hybrid. Such a hybrid allows for the integration of fiber and coaxial at a neighborhood location. This location, called a node, would provide the optical receiver that converts the light impulses back to electronic signals. The signals could then be fed to individual homes via coaxial cable.
Local Area Networks (LAN) is a collective group of computers, or computer systems, connected to each other allowing for shared program software or data bases. Colleges, universities, office buildings, and industrial plants, just to name a few, all make use of optical fiber within their LAN systems.
Power companies are an emerging group that have begun to utilize fiber-optics in their communication systems. Most power utilities already have fiber-optic communication systems in use for monitoring their power grid systems.

Fiber
by John MacChesney - Fellow at Bell Laboratories, Lucent Technologies
Some 10 billion digital bits can be transmitted per second along an optical fiber link in a commercial network, enough to carry tens of thousands of telephone calls. Hair-thin fibers consist of two concentric layers of high-purity silica glass the core and the cladding, which are enclosed by a protective sheath. Light rays modulated into digital pulses with a laser or a light-emitting diode move along the core without penetrating the cladding.
The light stays confined to the core because the cladding has a lower refractive index—a measure of its ability to bend light. Refinements in optical fibers, along with the development of new lasers and diodes, may one day allow commercial fiber-optic networks to carry trillions of bits of data per second.
Total internal refection confines light within optical fibers (similar to looking down a mirror made in the shape of a long paper towel tube). Because the cladding has a lower refractive index, light rays reflect back into the core if they encounter the cladding at a shallow angle (red lines). A ray that exceeds a certain "critical" angle escapes from the fiber (yellow line).

STEP-INDEX MULTIMODE FIBER has a large core, up to 100 microns in diameter. As a result, some of the light rays that make up the digital pulse may travel a direct route, whereas others zigzag as they bounce off the cladding. These alternative pathways cause the different groupings of light rays, referred to as modes, to arrive separately at a receiving point. The pulse, an aggregate of different modes, begins to spread out, losing its well-defined shape. The need to leave spacing between pulses to prevent overlapping limits bandwidth that is, the amount of information that can be sent. Consequently, this type of fiber is best suited for transmission over short distances, in an endoscope, for instance.
GRADED-INDEX MULTIMODE FIBER contains a core in which the refractive index diminishes gradually from the center axis out toward the cladding. The higher refractive index at the center makes the light rays moving down the axis advance more slowly than those near the cladding. Also, rather than zigzagging off the cladding, light in the core curves helically because of the graded index, reducing its travel distance. The shortened path and the higher speed allow light at the periphery to arrive at a receiver at about the same time as the slow but straight rays in the core axis. The result: a digital pulse suffers less dispersion.
SINGLE-MODE FIBER has a narrow core (eight microns or less), and the index of refraction between the core and the cladding changes less than it does for multimode fibers. Light thus travels parallel to the axis, creating little pulse dispersion. Telephone and cable television networks install millions of kilometers of this fiber every year.

BASIC CABLE DESIGN
1 - Two basic cable designs are:
Loose-tube cable, used in the majority of outside-plant installations in North America, and tight-buffered cable, primarily used inside buildings.
The modular design of loose-tube cables typically holds up to 12 fibers per buffer tube with a maximum per cable fiber count of more than 200 fibers. Loose-tube cables can be all-dielectric or optionally armored. The modular buffer-tube design permits easy drop-off of groups of fibers at intermediate points, without interfering with other protected buffer tubes being routed to other locations. The loose-tube design also helps in the identification and administration of fibers in the system.
Single-fiber tight-buffered cables are used as pigtails, patch cords and jumpers to terminate loose-tube cables directly into opto-electronic transmitters, receivers and other active and passive components.
Multi-fiber tight-buffered cables also are available and are used primarily for alternative routing and handling flexibility and ease within buildings.
2 - Loose-Tube Cable
In a loose-tube cable design, color-coded plastic buffer tubes house and protect optical fibers. A gel filling compound impedes water penetration. Excess fiber length (relative to buffer tube length) insulates fibers from stresses of installation and environmental loading. Buffer tubes are stranded around a dielectric or steel central member, which serves as an anti-buckling element.
The cable core, typically uses aramid yarn, as the primary tensile strength member. The outer polyethylene jacket is extruded over the core. If armoring is required, a corrugated steel tape is formed around a single jacketed cable with an additional jacket extruded over the armor.
Loose-tube cables typically are used for outside-plant installation in aerial, duct and direct-buried applications.

3 - Tight-Buffered Cable
With tight-buffered cable designs, the buffering material is in direct contact with the fiber. This design is suited for "jumper cables" which connect outside plant cables to terminal equipment, and also for linking various devices in a premises network.
Multi-fiber, tight-buffered cables often are used for intra-building, risers, general building and plenum applications.
The tight-buffered design provides a rugged cable structure to protect individual fibers during handling, routing and connectorization. Yarn strength members keep the tensile load away from the fiber.
As with loose-tube cables, optical specifications for tight-buffered cables also should include the maximum performance of all fibers over the operating temperature range and life of the cable. Averages should not be acceptable.
Connector Types
Gruber Industriescable connectors

here are some common fiber cable types
Distribution Cable
Distribution Cable (compact building cable) packages individual 900µm buffered fiber reducing size and cost when compared to breakout cable. The connectors may be installed directly on the 900µm buffered fiber at the breakout box location. The space saving (OFNR) rated cable may be installed where ever breakout cable is used. FIS will connectorize directly onto 900µm fiber or will build up ends to a 3mm jacketed fiber before the connectors are installed.

Indoor/Outdoor Tight Buffer
FIS now offers indoor/outdoor rated tight buffer cables in Riser and Plenum rated versions. These cables are flexible, easy to handle and simple to install. Since they do not use gel, the connectors can be terminated directly onto the fiber without difficult to use breakout kits. This provides an easy and overall less expensive installation. (Temperature rating -40ºC to +85ºC).

Indoor/Outdoor Breakout Cable
FIS indoor/outdoor rated breakout style cables are easy to install and simple to terminate without the need for fanout kits. These rugged and durable cables are OFNR rated so they can be used indoors, while also having a -40c to +85c operating temperature range and the benefits of fungus, water and UV protection making them perfect for outdoor applications. They come standard with 2.5mm sub units and they are available in plenum rated versions.

Corning Cable Systems Freedm LST Cables
Corning Cable Systems FREEDM® LST™ cables are OFNR-rated, UV-resistant, fully waterblocked indoor/outdoor cables. This innovative DRY™ cable with water blocking technology eliminates the need for traditional flooding compound, providing more efficient and craft-friendly cable preparation. Available in 62.5µm, 50µm, Singlemode and hybrid versions.

Krone Indoor Outdoor Dry Loose Tube Cable
KRONE’s innovative line of indoor/outdoor loose tube cables are designed to meet all the rigors of the outside plant environment, and the necessary fire ratings to be installed inside the building. These cables eliminate the gel filler of traditional loose tube style cables with super absorbent polymers.

Loose Tube Cable
Loose tube cable is designed to endure outside temperatures and high moisture conditions. The fibers are loosely packaged in gel filled buffer tubes to repel water. Recommended for use between buildings that are unprotected from outside elements. Loose tube cable is restricted from inside building use, typically allowing entry not to exceed 50 feet (check your local codes).

Aerial Cable/Self-Supporting
Aerial cable provides ease of installation and reduces time and cost. Figure 8 cable can easily be separated between the fiber and the messenger. Temperature range ( -55ºC to +85ºC)

Hybrid & Composite Cable
Hybrid cables offer the same great benefits as our standard indoor/outdoor cables, with the convenience of installing multimode and singlemode fibers all in one pull. Our composite cables offer optical fiber along with solid 14 gauge wires suitable for a variety of uses including power, grounding and other electronic controls.

Armored Cable
Armored cable can be used for rodent protection in direct burial if required. This cable is non-gel filled and can also be used in aerial applications. The armor can be removed leaving the inner cable suitable for any indoor/outdoor use. (Temperature rating -40ºC to +85ºC)

Low Smoke Zero Halogen (LSZH)
Low Smoke Zero Halogen cables are offered as as alternative for halogen free applications. Less toxic and slower to ignite, they are a good choice for many international installations. We offer them in many styles as well as simplex, duplex and 1.6mm designs. This cable is riser rated and contains no flooding gel, which makes the need for a separate point of termination unnecessary. Since splicing is eliminated, termination hardware and labor times are reduced, saving you time and money. This cable may be run through risers directly to a convenient network hub or splicing closet for interconnection.

What's the best way to terminate fiber optic cable? That depends on the application, cost considerations and your own personal preferences. The following connector comparisons can make the decision easier.Epoxy & PolishEpoxy & polish style connectors were the original fiber optic connectors. They still represent the largest segment of connectors, in both quantity used and variety available. Practically every style of connector is available including ST, SC, FC, LC, D4, SMA, MU, and MTRJ. Advantages include:• Very robust. This connector style is based on tried and true technology, and can withstand the greatest environmental and mechanical stress when compared to the other connector technologies.• This style of connector accepts the widest assortment of cable jacket diameters. Most connectors of this group have versions to fit onto 900um buffered fiber, and up to 3.0mm jacketed fiber.• Versions are. available that hold from 1 to 24 fibers in a single connector.Installation Time: There is an initial setup time for the field technician who must prepare a workstation with polishing equipment and an epoxy-curing oven. The termination time for one connector is about 25 minutes due to the time needed to heat cure the epoxy. Average time per connector in a large batch can be as low as 5 or 6 minutes. Faster curing epoxies such as anaerobic epoxy can reduce the installation time, but fast cure epoxies are not suitable for all connectors.Skill Level: These connectors, while not difficult to install, do require the most supervised skills training, especially for polishing. They are best suited for the high-volume installer or assembly house with a trained and stable work force.Costs: Least expensive connectors to purchase, in many cases being 30 to 50 percent cheaper than other termination style connectors. However, factor in the cost of epoxy curing and ferrule polishing equipment, and their associated consumables.Pre-Loaded Epoxy or No-Epoxy & PolishThere are two main categories of no-epoxy & polish connectors. The first are connectors that are pre-loaded with a measured amount of epoxy. These connectors reduce the skill level needed to install a connector but they don't significantly reduce the time or equipment need-ed. The second category of connectors uses no epoxy at all. Usually they use an internal crimp mechanism to stabilize the fiber. These connectors reduce both the skill level needed and installation time. ST, SC, and FC connector styles are available. Advantages include:• Epoxy injection is not required.• No scraped connectors due to epoxy over-fill.• Reduced equipment requirements for some versions.Installation Time: Both versions have short setup time, with pre-loaded epoxy connectors having a slightly longer setup. Due to curing time, the pre-loaded epoxy connectors require the same amount of installation time as standard connectors, 25 minutes for 1 connector, 5-6 minutes average for a batch. Connectors that use the internal crimp method install in 2 minutes or less.Skill Level: Skill requirements are reduced because the crimp mechanism is easier to master than using epoxy. They provide maximum flexibility with one technology and a balance between skill and cost.Costs: Moderately more expensive to purchase than a standard connector. Equipment cost is equal to or less than that of standard con¬nectors. Consumable cost is reduced to polish film and cleaning sup-plies. Cost benefits derive from reduced training requirements and fast installation time.No-Epoxy & No-PolishEasiest and fastest connectors to install; well suited for contractors who cannot cost-justify the training and supervision required for standard connectors. Good solution for fast field restorations. ST, SC, FC, LC, and MTRJ connector styles are available. Advantages include:• No setup time required.• Lowest installation time per connector.• Limited training required.• Little or no consumables costs.Installation Time: Almost zero. Its less than 1 minute regardless of number of connectors.Skill level: Requires minimal training, making this type of connector ideal for installation companies with a high turnover rate of installers and/or that do limited amounts of optical-fiber terminations.Costs: Generally the most expensive style connector to purchase, since some of the labor (polishing) is done in the factory. Also, one or two fairly expensive installation tools may be required. However, it may still be less expensive on a cost-per-installed-connector basis due to lower labor cost.Feed

Concrete casts new light in dull rooms

" title="Atom feed"Light transmitting concrete is on sale from this year.
The days of dull, grey concrete could be about to end. A Hungarian architect has combined the world’s most popular building material with optical fiber from Schott to create a new type of concrete that transmits light.
Letting the light in
A wall made of “LitraCon ” allegedly has the strength of traditional concrete but thanks to an embedded array of glass fibers can display a view of the outside world, such as the silhouette of a tree, for example.
“Thousands of optical glass fibers form a matrix and run parallel to each other between the two main surfaces of every block,” explained its inventor Áron Losonczi. “Shadows on the lighter side will appear with sharp outlines on the darker one. Even the colours remain the same. This special effect creates the general impression that the thickness and weight of a concrete wall will disappear.”
Light-transmitting concrete
The hope is that the new material will transform the interior appearance of concrete buildings by making them feel light and airy rather than dark and heavy.
Losonczi, a 27 year old architect from Csongrád recently came up with the idea while he was studying at the Royal University College of Fine Arts in Stockholm, Sweden. After demonstrating the material at design exhibitions all over Europe he has now formed a company to commercialize the concept.
His new company, also called LitraCon, is now optimizing its manufacturing methods and hopes to start selling prefabricated blocks of the material later this year.
Commerical possibilities
“In theory, a wall structure built out of the light-transmitting concrete can be a couple of meters thick as the fibers work without any loss in light up to 20 m,” explained Losonczi. “Load-bearing structures can also be built from the blocks as glass fibers do not have a negative effect on the well-known high compressive strength of concrete. The blocks can be produced in various sizes with embedded heat isolation too.”>Site Feed

Market report: Optical MEMS: the future of all-optical networks

The emerging field of optical micro-electromechanical systems promises to take a key role in telecoms networks. Phillip Hill looks at Europe's strengths in this field.
Lucent's micromirrors
A recent report from market-research firm Yole Développement of Lyon, France, stresses that, although Europe has a rich and high-quality R&D environment in optical micro-electromechanical systems, little of the research into these devices has filtered down to the manufacturing floor.
Eric Mounier from Yole Développement commented: "Many research institutes cover the same field of development, but often with insufficient resources."
The optical telecommunications market is growing at a dramatic rate. According to market-research firm RHK, the fibre-optic-component market will increase from USD 5.5 billion in 1999 to USD 21.3 billion in 2003 (an annual growth rate of 40%).
Driving demand
The development of dense wavelength division multiplexing (DWDM) has led to an unprecedented increase in the demand for optical components. DWDM systems currently use the expensive optics-to-electronics-to-optics (OEO) conversion to route and switch optical signals.
Deploying DWDM in optical rings in a cost-effective way requires optical add-drop multiplexers and optical cross-connects to overcome the need for OEO conversion.
Currently there are five competing technologies that are used to produce optical components: integrated optics, fibre optics, thin films, micro-optics and micro-electromechanical systems (MEMS)/optical MEMS.
As far as the MEMS technologies are concerned, there are two kinds of microsystems. MEMS are passive components - V-grooves and alignment parts, for example. Optical MEMS are microsystems for wavelength handling, either with a wavelength shift (this type of component uses materials other than silicon, such as InP) or without a wavelength shift, such as micromachined micromirror arrays or optomechanical switches.
In Europe there are about 10 companies that make optical MEMS products - mainly optical switches. For example, Ilotron - a spin-off from the Photonic Networks Research Centre at the University of Essex in the UK - develops all-optical network routers based on optical MEMS. Ilotron also integrates micromirror technology from several firms, including OMM in the US.
Compared with the US, few European businesses make optical MEMS products. "The development cost of these technologies is high and can scarcely be afforded by small firms. Ilotron is an exception, because it does not make components but integrates them into systems," said Mounier.
The other principal companies involved in MEMS are: Amic of Sweden, Optical Micro Devices of the UK, Optospeed of Switzerland, Piezosystem Jena, Germany, and Sercalo Microtechnology, Lichtenstein. New players are emerging, including CSEM in Switzerland, TMP in the Netherlands (now Kymata Netherlands) and Tronic's Microsystems in France.
Micromirror switch
The most commonly marketed active component is the optical switch. Sales in optical-switching systems are forecast to grow from USD 247 million in 2000 to USD 4 billion in 2004, according to market-research firm Pioneer Consulting.
IMM Mainz in Germany makes an optical switch based on polymer technology, while the start-up company Sercalo Microtechnology is developing a device that is based on silicon micromirror technology. Piezosystem Jena has optical switches that are based on piezoceramic actuation technology. The company is still developing its range of optical-fibre switches, with new developments ongoing (for example, a 4 ¥ 4 matrix and a 1 ¥ 16 fibre optical switch). LEOM (France) is currently developing a tunable filter based on InP material.
Large development costs
The most complex components that can be manufactured using optical MEMS technology - optical cross-connects for network management, for example - are currently being developed by large companies that can afford the development costs. Demand is not uniform in the network, so there is a growing need for reconfiguration of parts of it (to create regions of higher capacity). Optical MEMS, such as WDM add/drop, optical cross-connects and optical switches, are suitable for reconfiguration.
According to market-research firm ElectroniCast, the global consumption of optical add-drop multiplexers will grow from USD 23 million to USD 1.64 billion in 2003 and to USD 7.2 billion in 2008.
MEMS technology is ideal for large (more than 1000 ¥ 1000 inputs/outputs) optical cross-connects that can reconfigure the network in a short time (less than 50 ms) in response to traffic flow. Moreover, MEMS are free-space devices and each wavelength channel is physically separate from its neighbour. They could be the answer to the debate on all-optical versus OEO conversion.
Access to manufacturing is a vital issue for companies that are looking for optical MEMS products. There are two kinds of player: manufacturers with low intellectual property rights (IPR), such as Tronic's Microsystems, and IPR players without production units, such as Xros in the US.
In Europe, industrial transfer and creation of start-ups are strongly encouraged, even in state-owned laboratories.
Mounier said: "A European belief is that the creation of employment will emerge from the setting up of new start-ups by research institutes and laboratories. Europe is aware that optical MEMS added value is in the system and subsystem and not in the component itself. That is why the marketing position of Ilotron is so interesting."
Established microsystem foundries are now moving into optical MEMS activities. This is true for Twente Microproducts in the Netherlands, Gefran Spa in Italy and Tronic's Microsystems (which now makes micromirrors). Some firms prefer to be component integrators - such as Alcatel, which buys optical MEMS from OMM in the US.
There are few organizations that develop and manufacture components; this is a crucial point for the telecoms players that need access to production facilities.
"Companies are being acquired earlier and earlier in their development cycle," said Mounier. "Large businesses are gambling on not-yet-proven technologies."
US firms have more mature products that use optical MEMS technology than European companies, says Mounier. "US businesses have made major breakthroughs in optical MEMS. Industrial products that integrate optical MEMS were presented for the first time at OFC 2000.
"One strength of the US MEMS industry is the presence of 'open' MEMS foundries that offer custom optical-MEMS devices. Europe lacks such facilities, but there is a trend towards offering customized devices."
In pole position
Optical-MEMS activity in the US is a few years ahead of that in Europe. Large companies, for example Lucent Technologies and Texas Instruments, have developed large-matrix cross-connects using micromirrors as the base element. Moreover, says Mounier, amazing technological achievements have been realized by start-ups. Such performances force European firms to use US companies as providers.
In the field of optical MEMS, Europe has an excellent research base, a well qualified workforce and a strong knowledge base. It also enjoys a top-ranking position in complementary microsystem technologies, such as micro-optics and replication techniques as well as in packaging and interconnect techniques. In theory, Europe should be well placed to exploit a booming market.

ENGINEERS