Fiber Optic Update

Fiber optics, as we all know, has not had a very good time the last couple of years, with the overall market dropping by almost 80 percent (see chart at top right). But most of the problems were a result of the investment “bubble” caused by all of the hype over the Internet and ridiculous predictions of the future of telecommunications. Fiber has basically had a market “adjustment,” returning to reality.

Not all fiber optics is suffering; it’s mostly outside plant telecommunications that has had a hard time. If you talk to component suppliers and installers, the premises market, including LANs, security systems and industrial networks, is doing quite well. But the severe drop in the total market has caused steep price declines; one speaker quoted prices for optical fiber that were lower than kite string and fishing line!

Unfortunately, most manufacturers address both markets, so the drop in OSP sales has forced cutbacks in investments in all aspects of fiber R&D, limiting the new products and technology coming to market at this time. However, two product areas, laser-rated high-bandwidth multimode fiber and long-wavelength VCSELs have made promising strides.

We discussed the laser-rated multimode fibers in the June 2003 issue. The advent of gigabit networks created a problem for current 62.5/125 multimode fiber; bandwidth constraints limited its use in campus-style networks to a maximum length capability of 300m. Manufacturers dusted off a 25-year-old design for 50/125 fiber and offered it as a solution for gigabit links up to 500m. Users were reluctant to adopt this fiber, since the additional distance capability was not enough to overcome the inconvenience of its incompatibility with current fibers and higher price.

But after a couple of years on the market, the 50/125 fiber has become popular enough that its manufacturing volume has reduced the cost to actually make it about 10 percent cheaper than the 62.5/125 fiber. A move to 10 gigabit networks has required fiber manufacturers to spend some R&D bucks improving the 50/125 fiber to allow use at even higher bandwidths. Now the end user has three fibers to choose from: 62.5/125, 50/125 and the new ultra-high-bandwidth 50/125.

The choice, as always, involves tradeoffs. If the building or campus already has 62.5/125 fiber cabling, a move to either type of 50/125 requires thorough marking of the cable types and careful segregation of the two incompatible cable plants and all the patchcords. Then there is the issue of further changes in the technology that can make other options more viable.

The big question mark today is the future of a new type of laser source, the VCSEL (for vertical cavity surface-emitting laser), which is finally becoming available at 1310nm. You may remember that Gigabit Ethernet was too fast for the LED sources used in slower networks, so a newly developed device, the VCSEL, was adopted. This VCSEL, operating at 850nm (usually called “short wavelength” in fiber optic parlance) could easily handle the data rate and was compatible with the installed base of multimode fiber.

What made the 850nm VCSEL really popular was its cost. Using new fabrication techniques, VCSELs could be made about as cheaply as LEDs. Manufacturers have also been working on VCSELs at 1310nm, which would be compatible with both single-mode and multimode fibers, but the technology was much more difficult to develop. Just recently, two manufacturers have introduced devices and are shipping sample quantities. Given some time to ramp up production, these devices should reduce the cost of 1310 laser transmitters substantially, perhaps as much as 75 percent.

This is really good news for every aspect of fiber optics. Telcos and CATV companies can use these to reduce link costs and it might even encourage the adoption of fiber to the home. Premises networks benefit also. Using 1310nm VCSELs with single-mode fiber means that relatively inexpensive links can go really long distances—not 300, 500 or 2,000m, but 20km or more.

The 1310nm VCSEL can be also used with all the installed base of premises cabling, even one that was installed 15 years ago. Many backbone fiber optic cables already have both multimode and singlemode fiber, something many of us in the industry have encouraged for a long time, assuming that network speeds would eventually require the unlimited bandwidth of singlemode fiber.

But this new laser does not solve the dilemma of what type of multimode fiber to install. There is no question that the higher performance of 50/125 fiber will be required for 10 gigabit networks, which is where LAN backbones will be shortly. Perhaps now is the time to bite the bullet, start planning the upgrade, then install enough 50/125 fiber that all services can be switched over to it. Once the switchover occurs, the 62.5/125 fiber can be retired. Just remember, whenever you install new backbone cabling, install a hybrid cable with lots of singlemode fibers too—the price is right. EC

HAYES is a VDV writer and trainer and the president of The Fiber Optic Association. Find him at


About the Author

Jim Hayes

Fiber Optics Columnist and Contributing Editor
Jim Hayes is a VDV writer and trainer and the president of The Fiber Optic Association. Find him at .

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