April 15, 2009 • TV Technology • www.tvtechnology.com Page 10
LAS VEGAS - The Stratosphere observation tower is one of Las Vegas' signature landmarks, with its restaurants and high altitude thrill rides. At 1,149 feet, the tower, which is the tallest free-standing observation tower in the United States, also serves as camera platform and microwave receive site for local television stations.
KTNV the local ABC affiliate, and owned by Journal Broadcast Group of Milwaukee, Wis., has long had an analog camera and microwave receiveratop the structure, with a single-mode fiber link to its studios several miles away. To get more utility out of the fiber link as part of its BAS upgrade to a new MRC Central Receiver, the station installed a MultiDyne CWDM (Coarse Wave-Division Multiplexer) 2000 system.
"MultiDyne offers Journal cost effective and reliable ways to transmit multiple signal types over a single fiber link," said Ron Adair, director of television engineering for the Journal Broadcast Group. "That enables us to have Ethernet control of the system without the need of separate phone lines."
MultiDyne's CWDM system uses advances in laser and thin film technology that have made it economically possible to provide up to 18 different wavelengths on a single fiber, separating them by 20nm. "The CWDM2000 is basically a passive device," said Bob McAlpine, MultiDyne vice president of Global Sales & BusinessDevelopment in Locust Valley, N.Y. "It is set up to multiplex many different wavelengths of light into a single fiberpath. The criterion for the design was to provide the correct signal functionality over the existing single fiber line."
The station chose an eight channel CWDM-2000-8 for the job, which provides them with three spare channels. The CWDM-2000 is available configured for 4, 8, 12, 16 and 18 wavelengths, and with a pair of de-multiplexers, it could support 18 channels in each direction.
"There's essentially four links going through this fiber," said Scott Michaels, customer service manager for systems integrator Heartland Video Services of Plymouth, Wis., which designed and installed the MultiDyne system for the station. "We're multiplexing Ethernet capability between the studio and their site up there, we're multiplexing analog video and audio from the existing camera, and then we're taking back ASI from that central receive site."
Michaels gives high marks to the flexibility of MultiDyne's modular design. "One of the beauties of MultiDyne is that it's got a bunch of modules, and you can mix and match those to meet your specific requirements. So we were able to get Ethernet, analog video and audio, ASI, and leading edge 3-Gig HD-SDI fiber transport."
Where previously control of the receive site and camera was via four wire modem communication, and the video and audio path were limited, control is now handled via Ethernet. MultiDyne EM316SW-XY transceiversare installed at both the Stratosphere and studio ends.
An HD-3000 transmitter on the tower and receiver module at the studios will allow KTNV to install a high definition camera at its Stratosphere location, and is future-proofed to 3 GHz when there's need to deliver 1080/60p video.
A DTV-120 transmitter at the towerand receiver at the station are used to carry the ASI signal from the MRC central receiver back to the studios, and a DVM-2000 transmitter and receiver are used for the analog videoand audio from the current camera onthe tower. In all, the installation occupies five rack units of space.
Prior to shipping the equipment, MultiDyne engineers configure the CWDM-2000 units to the specified laser wavelengths. Since some users are accessing dark fiber and have no idea whether it is of the single-or multi-mode type, the CWDM units can be set up to handle either of them.
A coarse wavelength-division multiplex system uses uncooled lasers, which are relatively inexpensive compared with the cooled lasers necessary for DWDM (dense wavelength division multiplexing). The DWDM systems require such temperature control because individual wavelength channels are set only 3nm apart, which allows them to pass over 100 wavelength channels over a single fiber optic path.
The Stratosphere is the tallest free standing observation tower in the United States and home to microwave operations for Las Vegas stations.