plik

P P E N D I X

IBER

PTIC

TANDARDS

Widespread use of any technology depends on the existence of acceptable stan-
dards. Standards must include primary measurement standards, component stan-
dards, network standards, standard test methods, and calibration standards. In
fiber optics, this means standardized specifications for fiber, cables, connectors,
and splices and test procedures for fibers, cables, connectors, and splices under
many varying environmental conditions. Primary and transfer standards for opti-
cal power, attenuation, bandwidth, and the physical characteristics of fiber are
also required.

These standards are developed by various groups working together, all of

which  are  listed  with  contact  information  in  Appendix  C.  Network  standards
come from American National Standards Institute (ANSI), Institute of Electrical
and  Electronics  Engineers  (IEEE),  International  Electrotechnical  Commission
(IEC), International Organization for Standardization (IOS), Telcordia (formerly
Bellcore),  and  other  groups  worldwide.  The  component  and  testing  standards
come from some of these same groups, as well as from the Electronic Industries
Alliance (EIA) in the United States and internationally from the ISO and IEC, and
other  groups  worldwide.  Primary  and  transfer  standards  are  developed  by
national standards laboratories such as National Institute of Standards and Tech-
nology (NIST), formerly the National Bureau of Standards which exist in almost

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all countries to regulate all measurement standards. International cooperation is
available to ensure worldwide conformance to all absolute standards.

We must also discuss “de facto” standards, those generally accepted stan-

dards for components and systems that are widely accepted in the marketplace.
In fact, we want to discuss all of those and their status in today’s fiber optic sys-
tems.

DE FACTO STANDARDS COME FIRST

In any fast developing technology such as fiber optics, there is always resistance
to the development of standards. Critics say standards stifle technology develop-
ment. Some critics object because it is not their standard that is proposed, and in
some cases, nobody really knows what standards are best because the technology
is still under development. Given these circumstances, users must choose the best
solutions for their problems and forge ahead. In fiber optics, those who have
gone ahead and committed heavily to the technology or who have marketing
strength have established many of today’s standards.

In telecom systems, there are many types of systems but all are operating on

singlemode fiber at 1310 or 1550-nm wavelengths. Bit rates of 1.544 Mbits/S up
to 2.5 Gbits/S are already in operation, with wavelength division multiplexing
(WDM) giving much higher rates. Today, Synchronous Optical Network
(SONET) in the United States or Synchronous Digital Hierarchy (SDH) in the rest
of the world is the network protocol of choice. That appears to be changing as
the effect of the Internet drives everyone to Internet protocol (IP) networks.

In datacom systems (the generic category that includes datalinks and local

area  networks  [LANs]),  the  situation  is  reaching  consensus.  Four  multimode
fibers  have  been  used  in  datacom  systems:  50/125,  62.5/125,  85/125,  and
100/140 (core/clad in microns), but 62.5/125 fiber has been dominant. It origi-
nally  was  chosen  as  the  preferred  fiber  for  Fiber  Distributed  Data  Interface
(FDDI) and Enterprise System Connection (ESCON), became adopted by all ver-
sions of Ethernet, and the U.S. government is using 62.5/125 exclusively in offices
(FED STD 1070). Connectors have usually been ST style, but the EIA/TIA 568
Standard calls for the SC. The new small form factor (SFF) connectors are now
the multimode connector of choice for the networking equipment manufacturers,
as they offer higher density connections and reduce electronics cost.

While short wavelength light-emitting diode (LED) (820-850 nm) systems

have been most popular for Ethernet at 10 MB/s, the higher bit rates of faster
systems are requiring 1300-nm LEDs due to the limiting effects of chromatic dis-
persion in the fiber. The development of low-cost 850-nm vertical cavity surface-
emitting lasers (VCSELS) operating with multimode fiber has made Gigabit
Ethernet possible using lower-cost components, enhancing fiber optics as a net-
working technology.

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APPENDIX B — FIBER OPTIC STANDARDS

INDUSTRY STANDARDS ACTIVITIES

In light of these de facto standards, many groups are working to develop stan-
dards that are acceptable throughout the industry.

Primary Standards

The keeper of primary standards in the United States is the Department of Com-
merce, National Institute of Standards and Technology (NIST). Although some
optical standards work is done at Gaithersburg, Maryland, fiber optic and laser
activity is centered at Boulder, Colorado. Today, NIST is actively working with
all standards bodies to determine the primary reference standards needed and to
provide for them. With fiber optics applications, their concern has been with
fiber measurements, such as attenuation and bandwidth, mode field diameter for
singlemode fiber, and optical power measurements.

NIST standards are in place for fiber attenuation and optical power measure-

ments, the most important measurement in fiber optics. Since all other measure-
ments require measuring power, several years ago NIST ran a “round-robin” that
showed up to 3 dB differences (50 percent) in power measurements among par-
ticipants. An optical power calibration program at NIST has resulted in reliable
transfer standards at 850 nm, 1300 nm and 1550 nm. Using new transfer stan-
dards, measurements of better than 5 percent accuracy should be easily obtained.

Component and Testing Standards

Several groups are looking at fiber optic testing standards, but the most active by
far is the EIA in the United States and the ISO worldwide. EIA FO-6 and FO-2
committees  meet  at  least  twice  a  year  to  discuss  technical  issues  and  review
progress  on  the  writing  of  standards  test  procedures  and  component  specifica-
tions.  At  the  current  time,  there  are  over  100  EIA  fiber  optic  test  procedures
(FOTPs) in process or published and many component specifications are being
prepared. The EIA should be contacted for an up-to-date list of currently pub-
lished standards as well as those in process.

In addition to being a standards-writing body, the FO-6 and FO-2 commit-

tees are a forum for the discussion of technical issues, relevant to the FOTPs
being prepared, and are sometimes scenes of heated debate over these issues. But
real progress is being made in defining relevant tests for fiber optic component
and system performance.

Within the United States, Bell Communications Research (Bellcore), the spin-

off research and development organization for the divested Regional Bell Operat-
ing companies (RBOCs), was commissioned to set standards for its RBOCs by
issuing technical advisories (TAs) on subjects of mutual interest. Bellcore was
sold to a commercial company and renamed Telcordia, thus its impact on future
standards is unknown.

APPENDIX B — FIBER OPTIC STANDARDS

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Internationally, almost every country has its own standards bodies, but most

work through ISO and the IEC to produce mutually acceptable standards. The
IEC work is at least as large in scope as the EIA.

System Standards

Most early fiber optic systems were compatible with some electrical standards,
such as T-3, RS-232, and so forth, but each manufacturer used its own protocol
on the optical part of the network. As a result, there was little compatibility in
fiber optic systems. Even in telephony, fiber optic links developed as adapters for
standard T-carrier systems, so each manufacturer used its own protocol. Bellcore
developed SONET standards and CCITT did SDH to provide a standard proto-
col for telephony.

Work is now done by ANSI and IEEE on developing standard systems for

computer networks. The ANSI FDDI (X3T9.5 committee) is a high bit-rate sys-
tem for computer networks that has reached commercial reality. Another ANSI
committee (X3T9.3) is working on the even faster Fibre Channel specification for
GB/s  data  communications.  The  IEEE  standards  include  a  token-ring  LAN
(802.5), metropolitan area LAN (802.6), and fiber versions of all varieties of Eth-
ernet (802.3). From the vendor front, ESCON was developed by IBM to connect
mainframes to peripherals and has been adopted by the entire IBM-compatible
mainframe  industry.  Asynchronous  transfer  mode  (ATM)  is  a  fiber  or  copper-
based LAN using protocol borrowed from the telephony technology developed as
part of SONET and was developed into a LAN technology by an industry group
advocating  its  use.  So  network  standards  may  be  developed  by  any  number  of
groups who will then control the issues of compatibility and interoperability.

Standards change continuously. To keep informed on the current status of

fiber optic standards, contact the standards bodies involved for latest information.

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APPENDIX B — FIBER OPTIC STANDARDS