Scientific-Atlanta's Prisma DT transports video across the islands via fiber
MILILANI, OAHU, HAWAII
In 2001, Oceanic Time Warner Cable launched a plan to replace four headends, serving cable systems on the islands of Oahu, Maui, Hawaii and Kauai with a single, master headend. The challenge was finding a way to connect them. The result involved nearly 1,000 miles of fiber-optic cable.
"To streamline operating costs and improve operational efficiency, Oceanic Time Warner Cable wanted to collapse or remove the four individual headends and replace all of them with a single, master headend. So they've established a master headend in Mililani on Oahu that gathers all the signals -- whether broadcast, over the air or downloaded from satellites -- and processes them just one time, then sends them via a fiber-optic network to receive sites close to the HFC (Hybrid Fiber Coax) plants serving their customers on the four islands," says Thomas McCoy, director of product management, digital transport for Atlanta-based Scientific Atlanta.
"Because of the enormous, unprecedented distances that the video signals had to travel -- under the seas and across the four islands -- Oceanic Time Warner Cable chose the Scientific-Atlanta Prisma DT digital transport because it's the core component of a powerful, end-to-end solution dedicated to this high-performance (DVB-ASI) video transport application," he said.
The total distance of the network is 1,600 kilometers, but one link set a record distance for Scientific-Atlanta, according to Bob Collmus, director of product marketing and management, digital transport, for Scientific-Atlanta.
"Between Kaui and Maui is the largest fiber link ever supported by Scientific Atlanta -- 190 kilometers. This is about 20 to 30 kilometers longer than any other previous 'longest shot' distance," he said.
He added that the installation utilized undersea fiber-optic cable, with up to OC-48 capacity that had already been laid by the Hawaiian government.
ROUGH TERRAIN
"The architecture of this network, connecting four Hawaiian Islands, presented an immense geographical challenge. We had to resolve two pressing issues -- the distance itself and the quality of the fiber-optic cable over which the signal is traveling," Collmus said.
At the engineering site, "we did a number of OTDR (Optical Time Domain Reflectometer) measurements to determine if there was any impairment or delay time along the fiber-optic line that would promote signal loss," he said. "We then took those OTDR readings back to our lab and simulated those conditions to perform extensive tests. Once we were certain we could successfully transport video over that fiber distance without any signal loss, we moved it to the site for installation."
An external clock reference was used to synchronize the Prisma DT signals on all four islands, and Prisma DT "black boxes" placed at key hubs on the islands helped boost the transport signal along to the HFC plants. Also, the Prisma DT platform employs UPSR (Unidirectional Path Switched Ring) technology for redundancy, so that if a fiber cut occurs on any of the islands, the cable service will continue without interruption. (UPSR is a counter-rotating ring system, which is commonly used to ensure that the signal being transported would instantly switch to another fiber automatically to avoid disruption to the service.)
The entire installation also allows Oceanic Time Warner Cable to control, operate and monitor the entire operation, across the four islands, using Scientific-Atlanta's PC-driven TNCS (Transmission Network Control System) software from the master headend. Today, with the Prisma DT installation completed, "Oceanic Time Warner Cable now operates from its new master headend in Mililani on Oahu, which gathers all the signals -- whether broadcast over the air or downloaded from satellites -- and processes them just one time, and sends them via a fiber-optic network to receive sites close to the HFC (Hybrid Fiber Coax) plants serving their customers on the four islands," said McCoy.
"We've been able to consolidate many processes at the master headend in Mililani that used to be duplicated at each of our four headends. For example, we're able to perform signal delays that will shift programming from the Eastern U.S., (which is six hours ahead), and from the West Coast (which is three hours ahead) so that it airs at times more convenient to Hawaiian viewers," says Doug Stanfield, director of data networking for Oceanic Time Warner Cable, in Mililani, Oahu, Hawaii.
"The savings stem from eliminating expensive programming equipment, such as encoders and modulators, as well as technicians, power, AC and real estate costs associated with the individual headends," Stanfield added. "Real estate here in Hawaii is definitely at a premium."
With the additional space afforded by the new master headend in Mililani, the company can house the equipment needed to support new services, such as Video-on-Demand (VOD) and HDTV, utilizing Scientific-Atlanta's Explorer set-top boxes, as well as high-speed residential cable modem service.
