Fiber absorbs premises demands
In premises networks, multimode fiber-optic cable has proved to be a cost-effective medium for installation in campus backbones to distances of 2000 meters. Moreover, it is currently demonstrating equal performance in building cabling to 300 meters and horizontal cabling to 100 meters.
With little or no modification, multimode fiber accommodates a range of standard networking and transmission protocols; information rates; and voice, video and data transmissions. These capabilities provide additional cost savings because they readily adapt to premises network operations that have to be changed, expanded or upgraded.
To demonstrate the versatility of multimode fiber, the standards committee of the Telecommunications Industry Association Fiber Optics LAN Section has published premises fiber technology recommendations for standard local area network applications.
According to Steve Swanson, manager of standards engineering at Corning Inc., and a member of the Fiber Optics LAN Section standards committee, some network planners are not considering fiber-optic cables for the building cabling portion because most standards have been developed around backbone applications on networks longer than 2 kilometers. Minimal industry effort has been invested to standardize commercially available cost-effective solutions for fiber in premises runs less than 300 meters, notes Swanson. Yet, according to a recent AT&T study, runs of less than 300 meters represent more than 95% of combined horizontal and backbone intrabuilding cabling.
"Installing multimode fiber provides flexibility in upgrading networks because the cable plant remains intact. Only the electronics needs upgrading," says Swanson.
The standards committee believes that new and existing premises network applications should include cost-effective multimode fiber-optic solutions over distances of 300 meters and less. "Standards need to offer end users solutions that take advantage of available transmission technologies. When the full spectrum is presented, the advantages of fiber become clear," contends Swanson.
To demonstrate, the committee has tabulated recommended baud rates, fiber-optic cables and transmission technologies for campus, building and horizontal cabling applications. For example, it contends that 62.5/125-micron multimode fiber operating at 850 or 1300 nanometers can support horizontal cabling to 100 meters and building cabling to 300 meters for common communications standards.
For longer layouts, multimode fiber can handle most of the same communications standards except at some of the higher-speed transmissions. In those cases--622 to 2488 megabits per second for Sonet/ATM, for example--singlemode fiber fills the gap.
Fiber-optic cable is increasingly being installed in shorter building cabling and horizontal cabling networks. In fact, Electronicast Corp., a market research consultancy in San Mateo, CA, estimates that the installation of fiber-optic cable assemblies in premises data and local area networks should average an annual growth rate of more than 20% per year through 2003 (see page 53).
Fiber ribbons update
To the Editor:
As secretary of International Electrotechnical Commission Subcommittee 86A, I would like to comment on William Gardner`s article "Fiber Ribbons" (see Lightwave, January 1995, page 31). Several points in his article do not accurately reflect the situation as it stands today.
The document referred to in the paper was circulated in accordance with a parallel-voting procedure and referenced as IEC 1279; but when IEC Subcommittee 86A met in Istanbul, the document was approved as an international standard with the amended reference IEC 794-3 ("Optical fiber cables Part 3--Telecommunications Cables-- Sectional Specification").
Mr. Gardner says IEC 1279 was a "controversial document." In fact, it was submitted to the vote of IEC participating members according to IEC rules of procedure, and was accepted by a large majority. Vote results published by the IEC Central Office in April 1994 showed that 20 participating members sent in their ballots: 16 votes were positive, two negative, and two abstentions. Four additional positive votes were received from observer members but were not counted, in accordance with IEC rules. If by the words "controversial document" Mr. Gardner means that it has not been possible to obtain unanimous agreement, I agree. But when voting on a draft international standard, it is typical for a few national committees to cast a negative vote. Contrary to Mr. Gardner`s statement, the document was supported not only by Cenelec countries but also by several non-Cenelec, non-European countries.
The proposal submitted during the Istanbul meeting--to have work on ribbons as a stand-alone product in SC 86A Working Group 1 and work on ribbons as a cable element in the SC 86A Working Group 3-- was submitted to the vote of national committees as two distinct New Work Item Proposals, according to IEC rules of procedure. At the end of the voting period, a clear majority supported the work in SC 86A Working Group 3. However, the proposal to have Working Group 1 work on ribbons as a product did not meet either of the two acceptance criteria (a simple majority of participating members and at least five participating members willing to participate), so it was rejected. When Mr. Gardner says it is dangerous to attempt to shorten the international standardization process, he is right. However, his article shortened this process because the result of the vote has only just become known.
Finally, the reference to a sectional specification for optical fiber ribbon (IEC 1403-1) does not correspond to any official IEC document; even if some working group members have used such numbering, this can be confusing. The documents prepared for submission in a working group are just working documents and have no official status. They should not be referred to as IEC documents. In this particular case, this document has been canceled, since the corresponding work was stopped by the decision on the New Work Item Proposal.
In my opinion, since the beginning of these discussions on ribbons in the IEC, this issue has become very emotional for some people, probably because it has never been debated in depth. This may be due to limited time during plenary meetings. Such a discussion might be the only way to remove some of the bitterness and to stop the controversy.
Michel de Vecchis
Secretary of IEC SC 86A
Bezons, Cedex, France
Mr. Gardner replies:
Mr. de Vecchis` letter does contain new information: Since my column was written, the negative vote (10 to 9, with 3 abstentions) on the New Work Item Proposal has, indeed, stopped the work in Working Group 1 on ribbons as a stand-alone product.
Perhaps the additional discussion advocated by Mr. de Vecchis would help defuse this controversy. Some participants feel that the parallel-voting procedures followed in this case effectively bypassed and negated the specifications that were being developed by the IEC Working Groups, where such work normally occurs. The conflicting demands of rapid response and due process will continue to be a challenge for all standards organizations.