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Fiber: Truth or Fiction?

Fiber-optic cabling has become big business. In recent years, fiber's advantages over copper Cat-X and coaxial wiring have become clearer to a larger number of AV systems integrators. Still, misconceptions persist and it can be hard for integrators, installers, and end users to separate hype from reality. We gave it a shot.

"Fiber is signal-agnostic"

This is true in the sense that it will carry any type of signal, but integrators have to be aware that the signal itself can be proprietary, requiring the use of the same manufacturer's equipment at all terminations. That's contributed to a sense among AV integrators that standards don't exist for fiber transmission. "Down the road a fiber-optic standard will probably emerge," says Drake Wayson, president of national systems integrator General Projection Systems, based in the Orlando, Fla., area. "In the meantime, you have to think ahead about what kind of connectors are on the devices and stick with one brand for the entire facility."

But while Miranda acknowledges that AV integrators do have to be aware of proprietary differences between manufacturers' termination devices, he also stresses that standards for fiber do exist, citing the Society of Motion Picture and Television Engineers (SMPTE) 297-2006 specification. "The issue really is the fact that fiber has been used mostly in broadcast and IT applications up till now, areas where standards are required," says Miranda, who acknowledges that these standards aren't as readily apparent as fiber migrates to the AV community.

"SMPTE has defined a complete set of interoperability standards for the transmission of video and audio through fiber-optic interfaces, and the SMPTE 297-2006 standard even goes so far as to define fiber-optic connectors, power levels, and recommended methods for performance testing," Miranda says. The gulf between broadcast and IT on one hand and AV on the other, while narrowing in many ways as more AV utilizes Internet applications, remains wide because of misconceptions regarding connectors.

"Fiber is completely secure"

"A myth that applies to classified facilities is that fiber is magically secure," Wayson says. "It is not." He explains he learned that from working on various U.S. military installations, which he describes with military-like jargon as "fiber-intense."

"There used to be a sense that fiber was magically immune to being breached, but over the years the military has found that tapping into a fiber cable is not all that much more difficult than copper, so the protection of the cable system is just as important whether fiber or copper," Wayson says. Thus, making fiber cabling secure can be done in the same ways as for copper: conduits versus cable trays, and other ways to keep the cabling itself less accessible.

"Fiber is fragile and has bending issues"

Normal, PVC-jacketed fiber is actually very rugged. Because fiber-optic cable uses Kevlar as part of its construction, it can withstand a lot of abuse without breaking the internal glass fiber. Fiber cabling has a relatively tight bend radius–the radius of curvature that an optical fiber can bend without sustaining damage–equal to or better than that of Cat-6. A minimum bend radius is the radius below which an optical fiber or fiber-optic cable should not be bent. Larger radii bends are easier to pull and put less strain on the cable.

As a rule of thumb, TexelSPL's Mitchell says the minimum bend radius is generally 10 times the diameter of the cable–or six times the diameter of the buffered glass–or approximately 4 inches. "It's also a function of the wavelength," he adds, noting also that lower frequency waves navigate bends easier than higher frequencies, and they do it better in the wider 62.5-micron channels of multimode fiber than the 8.3-microns of single-mode. The single-mode wavelengths most common are 1310 nm, 1550 nm, and 1625 nm, while multimode wavelengths are commonly 850 nm and 1300 nm.

So if, for example, you have to pull a single-mode fiber-optic cable that's .75-inch in diameter around a 90-degree bend of conduit or wall, or your electrician wants to use a condulet and your 10-gigabit electronics are running 1550/1625 CWDM wavelengths, then the minimum bend radius would be 10 times the diameter of the cable, or .75 x 10 = 7.5 inches.

"I can do it all using copper"

You can, but you'd be severely restricting your range. For instance, DVI distribution maxes out at 5 feet to 10 feet over copper. In a medical education scenario that would require distribution of the same HD signal to five classrooms, five separate Blu-ray players would be necessary. SMPTE HD over coax could extend that reach to a little more than 100 meters, but using single-mode fiber cable, the HD signal from one Blu-ray player can reach more than 12 miles.

"Plus, [with copper] you'd be limiting what the installation can do in the future, as bandwidth requirements keep increasing," Jachetta says.

Fiber once was considered an exotic cable, but the convergence of AV and IT is putting it increasingly at the forefront of AV installations. Going forward, economies of scale won't only mean price drops for fiber cabling; it also will encourage more and easier-to-implement methods of installing, integrating, and terminating fiber. So if you haven't already, assume you'll be adding fiber to your AV diet very soon. That's the truth. AV

Dan Daley is a freelance AV writer based in Nashville, Tenn. He's a regular contributor to Hanley Wood media, covering pro and residential technology.

Tipping Point

Hybrid Matrix Routers

General Projection Systems (GPS) is a regular vendor to U.S. military installations, including Lockheed Martin's Center for Innovation and most recently the new Joint Forces Command's Joint Deployment Center in Norfolk, Va. For the past five years or so, fiber-optic cabling has been a regular proposition in these projects, thanks to the development of hybrid routers that can accommodate both fiber and copper.

"We would not have used fiber five years ago the way we do today," says GPS president Drake Wayson. "Five years ago it would have been strictly for security reasons or long distances. You had to do a conversion from fiber to copper transport outside the router, which was cumbersome, complex, and expensive.

"However, today it's possible to start out digital at a camera, for example, send it to a matrix, and end up at a codec and never have to [convert]," Wayson continues.

Over the past five years, end-point cost has come way down and flexible fiber matrix routers are more readily available from companies like

AMX/AutoPatch, CSI, Extron, and others. "The turning point for fiber came when we didn't have to convert back and forth ahead of or after the router," Wayson says. "'Digital flexibility' used to be an oxymoron," he says. "Now it's routine."







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