IntroductionThe design and planning of a facility-based optical fiber for Professional Audio & Video A / V transmission (Broadcast) should not be a problem for experienced system integrator or project engineer. But keep in mind that working with optical fiber is different from working with the distribution of copper wire. The optical fiber has unique and beneficial characteristics which can be exploited only if taken into account at the start during the planning stage. Here are 4 essential tips to consider when designing a fiber optic system for professional audio and video.
1 – Start with a blank sheet of paper.One of the most common mistakes when starting a new design using a fiber optic system or Audio and Video Transmission System (Broadcast) is to design the system with the traditional products of copper wire. Using design techniques and then substituting therein the optical fiber elements. Thus, restricting the use of fiber optic technology limits the copper cable. The fiber optic technology and products are susceptible to be implemented so that the copper wire can not be used as the bidirectional transmission of baseband signals, multiplexes several different signals with an optical fiber.
2 – Thinking in Audio & Video and Data.In the design of optical fiber, we may have to work with the IT staff of the facility or its consultants. Remember one thing: when it comes to how to understand baseband audio and video signals and how they communicate and the implications of any fiber optic infrastructure, IT people think very differently.
Although modern signals baseband audio and video to be transmitted over optical fiber is transmitted as “ones” and “zeros” and no data are transmitted as IT people used in IP packets, using various schemes compression. The biggest difference is that the band Audio and Video, including SDI, are transmitted unidirectionally without error detection or correction protocols. This results in a need of bandwidth much higher and a lower rate of bit errors to end infrastructure.
3 – Determine what kind of fiber optic needs.There are two types of fiber optic cables: multimode (MM) and single mode (SM). And they are not compatible. If the optical fiber is installed and there is no other option, it is imperative to know whether it is SM or MM, and if MM, what type of MM as 62.5 or 50 pm. Knowing what type of fiber is being used will be necessary for the specification of optical converters for the types of signals that communicate and other auxiliary equipment in the system. It is also used in calculating losses and estimate the maximum cable lengths. Given a choice, we recommend using SM fiber for its lower cost and higher bandwidth and low loss.
4 – Determining the lengths of the segments of optical fiber cable.It is important to know the lengths of the individual segments of an optical fiber, especially if the MM fiber is being used in one of the segments. When video signals are transmitted uncompressed baseband, such as HD-SDI, the bandwidth required distance severely limit the use of optical fiber dispersion due to MM. As a practical matter, this is usually not a concern with single-mode fiber, only in exceptional cases, such as long-distance calls.If you are forced to work with optical fiber segments of different types such as SM optical fiber between buildings and MM fiber inside the building, do not worry. There is active and passive equipment that can be deployed across different types of fibers successfully and some products on the market that work with both types of fibers eliminating this concern.