Triax vs. fiber-optic cable

Triax cable has a long and reliable history with broadcasters. It’s low cost and often the best choice for remotes. Photo courtesy Gepco International.

As remote television production transitions from SD to HD production, producers and remote facility companies face numerous issues. They must not only design new systems, but also implement the equipment for actual HD production. These issues include deciding among the different options for signal formats (1080i, 720p, 24p), recording formats, aspect ratio conversion, upconversion of existing material, surround sound, and even camera cable.

Faced with all of these choices and decisions, it's good to resolve them as soon in the production process as possible. One decision broadcasters should make early on is which camera cable to use.

Dispelling confusion

There are basically two ways to transmit an HD signal from the camera head to the base station in the truck: SMPTE standard multicore fiber-optic cable or triax. SMPTE fiber uses two single-mode fibers — copper for power and copper pairs for initial startup communications between the camera head and base station. Triax is basically heavy-duty coax with an extra shield. Power and data signals are combined and distributed as one across the copper conductors, riding along with the signal.

NEP Supershooters supplies SD and HD cameras that operate on either fiber or triax. Our staff has been directly involved for some time in the industry debate about the choice to use triax or fiber for remote productions. Let's examine some of the issues.

HD signals from the camera head are essentially uncompressed at 1.5Gb/s. The path from the camera to the base station is one of the few places where HD video has not been compressed. At first glance, this wide bandwidth might seem to suggest that fiber optics is the only way. But, for years, technology has been available to transmit the bandwidth-hungry digital signals from super-slow-motion cameras back to the truck on analog triax. This technology can offers the same ability to transmit HD from the camera to the base station.

Practicality and ease of use

But uncompressed digital transmission over triax is not currently practical over long distances. Using compressed digital signals introduces several seconds of delay because of the encoding process. Because of this, it is not easily implemented for live multi-camera HD production.

NEP Supershooters has found that using triax greatly simplifies setup in HD and that most stadiums and outside venues are currently wired for it.

Laying fiber is costly, from the standpoint of both equipment and labor. With SMPTE fiber cable running seven to eight times the cost of triax, few can afford to install SMPTE fiber and leave it there. So installation and removal are a major financial issue for the producer.

On the other hand, triax is easy to use. An experienced person can fix a piece of triax in a few minutes. If a triax cable gets cut, as it has during the half-time show at every Super Bowl telecast we have done, it can be repaired easily during a commercial break. That's not the case with fiber; the fiber cable must be returned to the shop for retermination.

The NEP Supershooters truck for World Wrestling Entertainment relies on triax for most broadcasts. This simplifies setup and if cable repairs are needed, they are easy and quick to make.

To protect against the potential of cut fiber cables at an event, we “home run” all the connections on the field to a central point, and use short pieces or “stingers” to the cameras. That way, if a cable is cut on the field, the staff replaces the stinger, not the home run. The real cost of fiber cable is in the termination. A 100ft stinger costs almost what a 1000ft does. With fiber, this gets expensive quickly.

Going the distance

Some stadiums have preinstalled single-mode fiber rather than SMPTE multicore cable. NEP Supershooters has adapters that work around the fiber by breaking out the glass, but this means that the camera must be powered from the closest electrical outlet or generator. It's just one more thing to go wrong if the power plug gets pulled or the generator quits.

The HD signals can travel farther on fiber, but triax covers significant distances (up to 2500ft over standard triax) — more than enough for most arena applications. Where longer runs are needed, a single strand of single-mode fiber is the solution. For an auto racing production, we use SD and HD triax cameras on Telecast Fiber Cobras with full camera features. It works well. It's single-mode, single-transfer over fiber, and the pictures are excellent. This method can take the camera out to 10,000ft with no problems.

For the majority of the shows where the cable does not have to go long distances, triax saves time, money and complexity.

Quality counts

There's also the issue of equipment reliability. One of our long-time clients, FOX Sports, has used both fiber and triax for Super Bowl XXVI, FOX NASCAR (including Daytona, where they used both fiber and triax) and the “NFL on Fox.” FOX Sports uses triax for most of its telecasts.

As for signal quality, HD cameras on triax won't yield a better picture to the home than would fiber. Ninety-nine percent of our clients request triax.

Ultimately, camera manufacturers need to develop cameras that can operate over triax or fiber. That would allow users to pick the solution that works best for each specific production on a camera-by-camera basis.

Our staff does a lot of talking with customers about our HD triax cameras and how they work, but not much about the cable. In many cases, they don't even think about the cable. NEP Supershooters has been to virtually every arena in the country, and the cable issue has never come up. That's because triax is transparent to what we do.

With fiber-only cameras, there's always the worry about how to get enough of the cable, get it installed in time and make it work. Sometimes it's not feasible to use an HD camera because there is simply no way to get fiber to the desired location.

With triax, there are none of these worries. Besides, you get the same results, in terms of picture quality, whether you use fiber or triax.

George Hoover is senior vice president of operations and engineering at NEP Supershooters.