Test your fiber-in-the-horizontal IQ

Sept. 1, 2000

Before you dismiss fiber for LAN applications, make sure you're up to speed on the technology.


With so many kilometers of optical fiber already installed, it's hard to believe that so many misconceptions about fiber still exist. However, many myths about fiber still live on-especially when you move beyond such "traditional" venues as telephony, cable television, and LAN backbones and risers. These misunderstandings may be preventing network managers from taking full advantage of an established technology that can help them build the networks of the future by using fiber to carry signals all the way to the desktops of their LANs.

Test your fiber-in-the-horizontal IQ with the 12 questions that follow. We also provide the answers, but if any of them come as a surprise, you may want to log onto the Website of the Fiber Optics LAN Section (FOLS) of the TIA. Our Website includes white papers, case histories, and resource directories that address the use of fiber-to-the-desktop (www.fols.org).

  1. Why is multimode optical fiber the most predominant medium for building backbones and risers?
    a) It supports the longest link distances
    b) It supports data rates up to 10 Gbits/sec and beyond
    c) It is highly reliable, minimizing network downtime
    d) All of the above
  2. Optical fiber is fully supported in which standards?
    a) TIA-568 (Commercial Building Wiring Standard)
    b) Gigabit Ethernet
    c) 10-Gigabit Ethernet (draft)
    d) All of the above
  3. Which advantages can be realized by deploying optical fiber in a centralized cabling network?
    a) Reduced costs
    b) Greater reliability
    c) Longer supported lengths
    d) All of the above
  4. 62.5/125-micron optical fiber offers performance characteristics (data rate and link lengths) that are roughly the equivalent of:
    a) Category 5 unshielded twisted-pair (UTP)
    b) Category 5E UTP
    c) Category 6 UTP
    d) Better than Category 6 UTP
  5. Why does optical fiber have a stronger tensile strength than copper, steel, and aramid yarn?
    a) It is made of ultrapure silica
    b) It has higher bandwidth
    c) It has lower attenuation
    d) All of the above
  6. Network managers who deploy optical fiber typically need to pull new cable:
    a) Every 2-3 years
    b) Every 3-5 years
    c) Every 5-7 years
    d) Once-when deployed
  7. Standard multimode optical fiber is used in:
    a) Backbones
    b) Risers
    c) Horizontal runs
    d) All of the above
  8. New small-form-factor connectors make fiber terminations:
    a) Less expensive
    b) Quicker
    c) Denser
    d) All of the above
  9. How many parameters must be field-tested to verify an optical-fiber network?
    a) One
    b) Two
    c) Three
    d) More than three
  10. To upgrade an optical-fiber network, which of the following typically do not need to be changed?
    a) The network electronics
    b) Any media-conversion elements
    c) The optical-fiber infrastructure and patch cords
    d) All of the above
  11. The proposed 100Base-SX standard:
    a) Provides a low-cost migration path from Ethernet to Fast Ethernet
    b) Uses 850-nm optics
    c) Is close to ratification
    d) All of the above
  12. Compared to copper-based systems, the cost for deploying fiber is:
    a) 15-20% higher for the initial installation
    b) Significantly lower over the life of the network
    c) Comparable in terms of labor costs
    d) All of the above
  1. (d) Multimode optical fiber offers network managers the three things they need in their network: long transmission distances, the ability to support high data rates, and low downtime. These characteristics are inherent in the medium, which has demonstrated it's proven performance for nearly two decades.
  2. (d) The use of optical fiber is fully supported for all standards and both current and proposed operating protocols.
  3. (d) Centralized cabling, TSB-72, was designed specifically to take advantage of the longer link lengths supported by optical fiber. Using a centralized cabling architecture, users can consolidate their electronics in a central closet, thereby also reducing network costs and improving reliability. The most recent revision of EIA/TIA-568B.1, due out in the next few months, will elevate the status of centralized optical-fiber cabling from a technical service bulletin to a normative annex.
  4. (d) It is difficult to compare multimode optical fiber to any existing or planned grades of UTP copper. Unlike copper, glass optical fiber offers inherently high bandwidth, making it a suitable transmission medium for planned as well as existing protocols. In addition, optical fiber is smaller, lighter in weight, and immune to electromagnetic and radio-frequency interference.
  5. (a) One of the surviving myths about optical fiber is that, because it is glass, it is fragile. Quite the opposite is true; made from ultrapure silica, optical fiber is very strong and rugged.
  6. (d) One of the greatest advantages in deploying optical fiber is that it supports network needs over the life of the installation. Many network managers find they need to pull new UTP cable each time they upgrade their networks to support new protocols, essentially shutting down their networks for weeks on end and incurring repeated labor costs. In contrast, multimode optical fiber has the bandwidth to support network upgrades without the need for pulling new cable.
  7. (d) Multimode optical fiber is used throughout LANs. While it has become the de facto standard for risers and backbones, network managers increasingly are deploying fiber in the horizontal, as well.
  8. (d) Small-form-factor connectors are helping to make optical fiber easier and more cost-effective to install in the horizontal. The new connectors have the same size footprint as traditional copper-based connectors. As a result, they help increase density and reduce the cost of hubs and switches, lower patch-panel and enclosure costs, reduce jumper costs, and reduce connector installation costs.
  9. (a) Testing optical fiber is easy. Since fiber-cable facilities are not affected by near-end crosstalk (NEXT) and their operating performance is not affected by frequency, they can be tested simply by measuring the attenuation of the optical-fiber link.
  10. (c) Upgrading a fiber-optic-based net work typically involves replacing only the electronics and media-conversion elements, so the fiber infrastructure can remain intact.
  11. (d) The proposed 100Base-SX standard provides network managers with a cost-effective migration path from Ethernet to Fast Ethernet because it uses low-cost, light-emitting-diode technology to achieve Fast Ethernet, providing network managers a cost-effective migration path from 10 to 100 Mbits/sec without changing to 1,300-nm electronics.
  12. (d) Perhaps the greatest myth that remains about deploying fiber is that the technology is cost-prohibitive. While there is still a slight premium over copper for installed first costs, that equation is changing with the development of new technologies and proposed standards (such as 100Base-SX). And if you take the viewpoint of the total cost of ownership of your LAN, fiber-based systems offer greater reliability and lower costs.

FOLS member companies include 3M, AMP, Allied Telesyn, Berk-Tek, Belden Wire & Cable, Comm Scope, Corning, LANCAST, Lucent Technologies, MicroLinear, Ortronics, Panduit, Siecor, Siemon Co., SpecTran, Sumitomo Electric Lightwave, and Transition Networks. For more information from FOLS, please visit www.fols.org.

Herbert V. Congdon, II, PE, is market manager, fiber, at AMP Netconnect Systems (Harrisburg, PA).

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