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Testing Multimode Fiber Gets International Attention
Multimode fiber R&D was shoved aside in the mid-80s when the phone companies switched to singlemode. With the continuing use for premises cabling, multimode remained popular, with 62.5/125 micron FDDI-grade fiber being the standard in the US. With the advent of Gigabit Ethernet, which uses VCSEL lasers, a new-old fiber re-emerged, 50/125, first as a 50/50 Mhz-km bandwidth design, then truly laser-optimized with a bandwidth of over 2000 MHz-km at 850 nm for VCSEL networks at 1-10 Gb/s or more.
But as the speed of networks increased, the loss margin decreased accordingly. Thus very high speed networks have loss margins of 2-4 dB, compared to 6-14 dB or more for 100 Mb/s networks like FDDI and fast Ethernet. With smaller margins, the need for accurate loss measurements became more critical.
At the same time, test equipment manufacturers lobbied to have OTDR testing recognized as acceptable for cable plant testing, just like light sources and power meters (LSPM is the European terminology, but many here use OLTS.) In Europe, draft standards already give them equal status, based on some tests conducted last year that showed correllation between OTDR and OLTS testing when certain commercial mode conditioners are used on both test sets.
The FOA decided to see if we could duplicate the results ourselves. We obtained several of these mode conditioners and TIA -pecified mandrels and tested some new-generation OM-3 fibers with both LSPM and OTDR. Our results are shown here (PDF). Our results:
We presented this material at a TIA standards meeting in February, which was good timing, as the meeting saw a number of other presentations on problmes with mode-dependent measurements. The issue has been deemed important enough that the TIA FO-4 committee has begun organizing an industry-wide task force to investigate the problems encountered with multimode measurements and determine the best solution, which can be written into US standards.
Don't expect a solution too quickly, as these processes take time, and this is a big one! However, the FOA is considering having our members help provide data by helping us gather information on the measurement uncertainty of testing a multimode cable plant. If you are interested in participating, let us know - email to firstname.lastname@example.org.
Technology Updates - Getting Closer To Optical Integrated Circuits
Two new developments in semiconductor technology offer promises for cheaper, faster fiber optic links and perhaps even a breakthrough on integrating optics into semiconductor chips.
The first development comes from
Professor Connie Chang-Hasnain at UC Berkeley, who has developed
a new simple way to make the mirrors required to create the laser
cavity on lasers like the VCSELs used for fiber optic links.
Normally, the mirrors are made by building up many layers (about
80) of semiconductor material. Professor Chang-Hasnain figured
out how to make the mirrors with an air gap and only one mirror.
Not only will this allow cheaper lasers, but they are thinner
and may be able to allow making VCSELs at wavelengths other than
850 nm, a current problem. This development promises to make
all VCSELs cheaper, not only for fiber optics, but for those
used in CD or DVD players. And the technology is so simple, that
commercialization should happen quickly.
The second development comes
from MIT, where they claim to have found a simple way to integrate
ICs and optical devices on a single chip. This has been hard
to devise, as ICs are generally based on inexpensive silicon
while optical devices require gallium arsenide or similar, more
complicated semiconductor materials. Details on the processes
used are sketchy, probably because a ton of patents are being
filed, but if it proves commercially feasible, it could make
fiber optics easier to implement - and justify.
The Fiber Optic Association Holds "Fiber To The Home Summit" in Los Angeles
The Fiber Optic Association, Inc. (The FOA) hosted a "Fiber To The Home" Summit Meeting on January 18, 2007 in Los Angeles at LA Trade Technical College. For full details on the meeting, including a rundown of the employment needs of Verizon which is looking for many FTTx techs around the US, see the February FOA Newsletter.
Fiber Optics Sales Engineer / Account Manager
For consideration, please send a cover letter with your resume attached (Word or PDF) to Human Resources at <email@example.com> . Lightwaves 2020, Inc. is an Equal Opportunity Employer.
Technical Applications Engineer
REPORTS TO: Director of Marketing & Sales
SUMMARY OF POSITION:
Excellent verbal and written
Please submit resume and references to:
Mr. Joseph Pagano, CFO
Tel. No. (908) 647-6601
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Your Name, CFOT - It pays to advertise!
The FOA encourages CFOTs to use the logo on their business cards, letterhead, truck or van, etc. and provides logo files on this site for that purpose. But we are also asked about how to use the CFOT or CFOS certifications. Easy, you can refer to yourself as "Your Name, CFOT" or "Your Name, CFOS/T" for example.
Feel free to use the logo and designations to promote your achievements and professionalism!
Remember To Renew Your Certification !
Remember to renew your FOA certification. All current CFOTs have a ID Card with their certification data and we keep a database of current CFOTs to answer inquiries regarding your qualifications if needed. You must be a current FOA member and CFOT to participate in our online database of installers, contractors, technicians and consultants. If you forgot to renew, use the online application form to renew NOW!