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Expert Roundtable: The State of Fiber

Mar 1, 2009 12:00 PM, By Bennett Liles

Four industry experts shed some light on the future of fiber.

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Hayes: Perhaps the biggest impact for the installer is the industry's move to make more usable, and cost-effective, preterminated fiber-optic systems — plug-and-play cables. They are made to order and simply require placement and connection. They cost more, but reduce installation labor time and cost. Plus, they perform as well as, or better than, most field-installed systems.

Some networks can now be connected with active cables — fiber-optic cables with media converters on each end that replace copper connections exactly. The biggest application now is in data centers for short, high-speed links. For those doing field terminations, practically every termination type has improved — especially the prepolished/splice-type connectors that now have lower and more acceptable losses when done with the new termination kits.

In case you missed it, fiber has become the media of choice for most applications at very high speeds or for video surveillance and wireless networks in large facilities. Why? The usual reasons: bandwidth and distance capability, lower power consumption, smaller size, easier to install.

Lopinto: Fiber technology is making incremental improvements in both transmission equipment and fiber cable all the time. Just look at the new product announcements that come from the manufacturers, particularly the small innovative ones, every week. But until those who influence the modus operandi of the AV industry truly decide to advance the state of the art beyond copper technology, its deployment will be slow.

What specific standards should AV tech people be familiar with in relation to installing fiber-optic lines and using fiber-transmission gear?

Commare: Know the terms. Understand the difference between multimode and single-mode. Keep connectors clean.

Spennacchio: In any digital system, the most important component is the clock. AV technicians should have a firm understanding of clock, how it works, clock distribution, etc. The other consideration is light budget. You need to know the overall light budget of the system, and pay attention to how many connections you have, as each connection contains some loss. Depending on the connector, this can be 1/2dB to 2dB of loss per connector. Also, if there is fiber already installed, you need to know if it is single-mode or multimode before you order the gear you want to transport over it.

Hayes: The most important thing to understand is building codes — they are the law. This is to prevent electrical shock, fires, and reduce the impact of fire. As for standards, most have been written for the component manufacturers, not installers. Some refer to cabling, some to electronic hardware or networks. Manufacturers are the best source of data on what standards mean to the installer.

Lopinto: One very specific and comprehensive standard is SMPTE 297-2006. This defines how all serialized, or SDI, video signals are transmitted over fiber. These signals include everything from standard-definition TV all the way up through 1080p HDTV. The standard defines the mechanical and optical interface specifications for both a transmitting and receiving device. It was adopted specifically to ensure compatibility and interoperability between fiber-optic equipment from different manufacturers. But, once again, those who hold sway over the standard practices of the AV industry seem to actively promote a one-vendor solution and employ equipment with proprietary interfaces. In the broadcast industry, these manufacturers would not stand a chance of selling their equipment. The broadcasters want the flexibility to buy best of breed and therefore demand equipment that conforms to standardized interfaces.

What are the most common mistakes to avoid when installing, testing, and troubleshooting fiber-optic installations?

Commare: Mismatching single-mode and multimode fibers. Mismatching multimode 50 and 62.5 micron fibers. Have the right equipment to troubleshoot your infrastructure. Label everything, and keep an updated drawing of all connections and patch panels. Did I mention keeping everything clean?

Spennacchio: Crimp the fiber when closing up a junction box; correctly connect and plan the distribution of clock; and make sure that fiber connectors are clean and fully connected.

Hayes: In our experience, the biggest mistake installers make is trying to do something when they do not know how to do it properly. We can cite some very expensive instances. A contractor pulled out $100,000 worth of perfectly good cable because he did not know how to use new equipment purchased to splice it, and he did not know how to read [optical time-domain reflectometer] OTDR traces.

Another installer had to retest over 1,000 12-fiber cables because he was told by a vendor that OTDR testing was acceptable instead of insertion-loss (light source/power meter) tests. He also used autotest on the OTDR because he did not know how to read OTDR traces, and it gave erroneous results — obvious to the customer.

Training is the answer, but it must be good training by qualified instructors, not a salesman. Secondly, it's important to have a good design for the network before starting installation and to manage the installation properly.

Lopinto: The first mistake to avoid is not to do it without the proper test equipment. It's amazing how many installations are done and then troubleshot without even a basic $200 optical power meter. It is like a pilot flying a plane without a compass.

The second mistake is not cleaning the tips of all the fiber connectors before installing them. Microscopic particles of dirt can attach themselves to the tips of the connectors and block the passage of light. It takes two seconds with a simple Kimwipe or alcohol pad to clean a connector. Without question, a dirty connector is the largest single cause of fiber-optic system problems both during the initial installation and over time.

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