Bridging the Gap

Fiber-optic solutions helps Australian city manage traffic, incidents

• By Megan Weadock
• Apr 01, 2010

In the days before fiber optics, certain surveillance applications simply weren't possible—or too expensive to even be considered feasible.

In the past, that would have been the case at the West Gate Bridge in Melbourne, Australia, where a fiber-optic solution from Infinova is now linking cameras to the city's video depot, miles away. West Gate is Australia's third-longest bridge, stretching a total of 8,473 feet across the Yarra River. The beautiful cable-stayed bridge, which was built in the 1970s, is twice as long as the Sydney Harbour Bridge.

Mark S. Wilson, Infinova's vice president of marketing, said the city chose Infinova because the company has completed many high-profile projects throughout Australia and Asia. The installation was finished in the first quarter of 2009.

"This bridge is just one of many major infrastructure projects that have turned to Infinova fiber optics for more efficient, quality transmissions of images," Wilson said. "Since high-performance surveillance systems require greater reliability and increased throughput, the leaps forward in CCTV system technology have increased the demand for Infinova fiber optics."

Keeping Watch

The West Gate Bridge installation includes an Infinova N3731 Series fiber-optic transmitter, which transmits one digitally encoded video channel with a bidirectional RS-232/RS-422 contact closure and DIP selectable data over one or two fibers.

The transmitter receives video from the PTZ dome camera on the bridge and delivers it to the West Gate Bridge Depot via fiber. Another N3731 Series transmitter collects the video at the depot. This enables security officers to monitor traffic and react quickly to any incidents on the bridge.

Video from the bridge is simultaneously distributed to an Infinova N3790 Series transmitter for transmission over a single fiber to Melbourne City for remote monitoring. Meanwhile, the transmitter sends PTZ control data to the dome cameras via fiber. As a result, officers who are several miles away can view and control the PTZ control function of the cameras on the bridge.

"[Prior to the new installation], there was a former surveillance system on the bridge, but it was a very basic set-up with limited coverage," Wilson said. "Authorities wanted a system that would let them see all parts of the bridge at all times in order to ensure orderly traffic flow and catch any pedestrians not authorized to be on the bridge."

Infinova's N3790 Series is a digitally encoded, expandable and flexible fiber-optics transmission system. Data formats support RS-232, RS-422, twowire/ four-wire RS-485, Manchester/Biphase and contact closures. The transmitters use CWDM technology to transmit up to 64 channels of NTSC, PAL or SECAM video, 32 channels of audio, 32 channels of data, 32 channels of contact closure signal or eight channels of intercom.

The Future of Transmission

Around the globe, the demand for high-performance surveillance systems—which require greater reliability and increased throughput—has in turn led to a greater demand for fiber optics. At the West Gate Bridge, for example, fiber optics better preserves the quality of video signals, providing a high level of security, transmitting at higher data transfer rates, operating at distances five times greater than coaxial cable and leading to lower signal losses, strong data protection and a longer life for the system.

"Because of the importance of this bridge, it was imperative to get more signals from the camera end to the monitor end over greater distances and in harsher environments," Wilson said.

The fiber-optic system also allows the bridge operators to leverage other, lesser-known benefits. For example, they are able to avoid problems with electromagnetic interference, radio frequency interference, cross-talk, lightning or ground loops.

"They also don't have to worry about short circuits, sparks or fire hazards with fiber," Wilson explained. "In addition, the large signal-carrying capacity of optical fibers makes it possible to provide not only many more signals, but also more sophisticated signals than could never be handled by a comparable amount of copper wire."

Wilson said the city of Melbourne plans to expand the system in the future, but the additions have not yet been finalized. For now, the city and its residents can know that its impressive bridge is safe and secure.