Fiber Optics in TV and Radio broadcasting

By Pavel Demidov

Review contents:

Fiber Optic technologies in broadcast sphere Profitt Company equipment for Fiber Optic links of video, audio and data transmission Axon equipment BKtel equipment for Fiber Optic networks Fiber Optics in TV and Radio broadcasting Kramer Electronics equipment for Fiber Optic lines of TV signal transmission Network Electronics equipment Snell & Wilcox Fiber Optic receivers and transmitters Equipment of Telecast Fiber Systems Company Optical node getting closer to the household Fiber Optic equipment from Vistek

Transmission of video signals and digital data over conventional copper cables can not yet comply with constantly growing requirements caused by signal quality enhancement and consequently bit rates as well as distances. The problem is that the resistance of coaxial cables and twisted pairs limits the distance which the signals can be transferred on. Moreover, in any system conductors operate as a huge antenna which suffers from interferences from very different sources including close placed conductors, electromagnetic fields from various devices etc.

Elegant and cheap solution of this problem is Fiber Optics. Optical fiber characterized much wider band with less loss than coaxial cable which allows transferring images with high resolution on pretty longer distances with no use of path amplifiers or repeaters. And since the signal transferred as a beam of light instead of electric current the system becomes fully secured from any kind of electric interference including neighbor conductors or high voltage power lines.

Unfortunately, working with a fiber of human hear in thickness will never be as simple as two conductors connection by means of clip and, of course, the very important meaning has the clearance. Besides, each end of line requires an interface for conversion electric signal to light beam and vice versa.

So why despite of it the constantly growing interest to the Fiber Optics use in TV and radio broadcasting and post-production is being seen today?

Advantages of Fiber Optic signals transmission

For many applications the Fiber Optics is preferred due to large number of advantages. Not all of them, nevertheless, are equal for different users. Most important in terms of implementation in TV systems are also mentioned low loss at transmission as well as wide band of optical fiber allowing simultaneously transferring video, audio and digital data over the single Fiber Optic cable. Besides recalled protection against interference and distortions it is important absence of ability to conduct electricity which eliminates problems caused by changing of earth potential and also exclude a danger of corrupting the equipment caused by current peaks as a consequence of lightning etc as well as provides galvanic separation.

Not of less importance is that what the compactness of these cables lets inject new life into fully populated cable channels. For example, the single coaxial cable occupies the same place as 24 Fiber Optic cables each of which as one can estimate is able simultaneously transfer 64 video channels and 128 audio channels.

Besides, Fiver Optic cable doesn’t getting old. By means of simple replacement of end equipment but not cables themselves Fiber Optic networks can be upgraded for transmission of higher volumes of information. From the other side, part of network or even whole network can be used for totally different task — for combining with local computing network or with IP telephony in the single cable, for instance.

B7741AV Series receiver and transmitter

B740AV/B7740AV Series devices

B748AV/B7748AV set

B72xA/B772xA Series equipment

The tasks being solved

As a rule, the necessity appeared to use existing single mode optical cables. Such cable is necessary to use to cover long distances (up to several tens of kilometers). The use of multi mode cable limits maximum distance up to three to five kilometers. In most cases on short distances it is more efficient using free fibers in existing (rented) cable than financing works on building new path.

The most popular task is transmitting the signal (video plus audio) over long distance from facility to TV transmitter or from satellite headend to facility.

GE Security/Fiber Options Company, one of the leading manufacturers, produces B741AV/ B7741AV product range.

Devices designed as modules for installation into the frame. The main feature is that the transmission is being done in digital domain but with no compression. 10-bit DAC/ADC for video is used providing 7.5 MHz signal bandwidth and over 67 dB S/N ratio. For audio signal 24-bit DAC/ADC is used; bandwidth is 20 Hz…20 KHz; S/N ratio is over 90 dB; harmonic distortions are less than 0.003%.

In the middle of 2004 Fiber Options Company had presented a new product — inexpensive B740AV/ B7740AV set. Principal differences from previous one are ability to make it as a standalone device and 8-bit video digitizing which narrows bandwidth of video transmission to 6.5 MHz and, consequently, decreases resolution to 520 TVL.

The use of up-to-date technologies, for example CWDM, allows explore single fiber (single mode or multi mode) for transferring of four video channels and eight audio channels with parameters equal to B741AV/ B7741AV.

Digital technologies let solve the wide specter of tasks, for instance duplex transmission of video and audio over the same cable. New B741AV/B7741AV set solves this tasks transferring video in 7.5 MHz bandwidth in duplex mode.

For transmission of component (YUV, RGB, and VGA) signal B780G/B7780G set is designed. The bandwidth for each component is 125 MHz which is enough for transmission, let’s say, UXGA signal.

For radio facilities B72xA/B772xA Series equipment produced which is designed for transmission one to four audio channels via single cable in both duplex and simplex modes.

Material provided by Balt Sys Ltd.