Fiber-optic transport
Oct 1, 2008 12:00 PM, By Jim Jachetta
As the demand for the transport of high-resolution video at higher bandwidths increases, the use of fiber in facilities will be more and more prevalent.
Systems can be designed using many of the technologies described above. We can mix analog and digital signal transport. We can combine signals using time-division and optical multiplexing.
A broadcast television station may typically reside in a downtown metropolitan area, while the television transmitter and satellite up and down links may be on a distant mountaintop outside the city. This situation is a perfect application for fiber transport. The system may require both analog video and DVB/ASI digital video, because the station might be in the midst of its conversion from analog to digital broadcast. It will also require signals in both directions to support downlink satellite video.
Another application is where many channels of video and audio are combined together over one fiber for backhaul feeds, cable television, common carrier or telco. The system uses time-division multiplexing (TDM) to combine groups of eight channels of video with audio into single wavelengths. The optical multiplexing (CWDM) technology is used to combine the wavelengths with groups of eight videos onto one fiber. The combined technique of TDM and CWDM provides a fiber transport capacity of more than 144 video channels on one fiber.
Fiber-optic video networking
Solutions are available to distribute video over large networks. The current trend is the transport of video, audio and data over an IP or Ethernet network. These systems require compression and a high-bandwidth infrastructure to move many signals at one time. IP systems can have issues with compression artifacts and latency due to limited network bandwidth, but they are simple in design and configuration.
Systems are available that offer the same simplified design and configuration, but in an uncompressed, real-time, high-quality video transport. These new systems transport and distribute uncompressed video, audio and data over fiber. This new technology drastically simplifies the architecture of a fiber-optic network, reduces equipment costs, simplifies design, and maintains uncompressed, digital, broadcast-quality video from end to end.
Fiber-optic transport technology has numerous applications in sports, ENG/SNG, field and studio production, broadcast, cable, satellite, and the studio to transmitter link (STL).
Figure 1. The fiber receivers can be integrated with the multiplexer into a fiber hub to save rack space.
Click to enlarge
In a traditional system, there are multiple fiber-optic transmitters at each video source. The fiber-optic signals are then typically routed to a central location or node. At the central location, the fiber-optic signals are converted back to analog video, audio and data. Then up to eight channels of video, audio and data are combined once again using TDM into a single fiber-optic signal. Two TDMs are required to transport 16 channels of video over one or two fibers. The equipment at the central node typically occupies 8RU to 10RU. The 16 channels of TDM video are then decoded at the receiving end using three or more rack units of equipment.
A new fiber transport system reduces the equipment required at the central node from 8RU to 10RU to 1RU or 2RU. (See Figure 1.) As in the traditional system, a fiber head is used at the source location to encode the video, audio and data onto one fiber. At the central location or node, the 16 fiber-optic receivers and two TDMs are combined into one device called the fiber hub. The fiber hub supports up to 16 fiber-optic inputs from up to 16 video fiber head units. The fiber hub unit has one high-speed, fiber-optic output for the main fiber.
| Want to use this article? Click here for options! |  |
