Fiber optic devices for receiving — transmitting video.
The main task of video surveillance systems is to transmit images over various distances with maximum quality and minimal losses. The solution to this problem when designing and installing a video system:
correct selection of equipment;
high-quality installation.
What questions arise when designing video surveillance systems:
what end equipment to use;
what transmission medium to use (wireless channel, copper cable, fiber optic).
We will not touch on the topic of selecting the final equipment (video cameras, monitors, etc.). Let us dwell in more detail on the questions: «What transmission medium is better to use?» and «What should be taken into account when choosing transceiver devices?»
In what cases is it advisable to use fiber optics for transmitting video images?
The answer to this question logically follows from the main advantages of using fiber optic communication lines:
better noise immunity compared to copper cable;
longer transmission distance (about 2 km via twisted pair cable, several tens (up to 50–70) km via fiber-optic communication lines);
higher bandwidth;
compactness (several hundred signals from various sources can be transmitted via one optical fiber using various multiplexing methods).
The conditions under which the use of optical fiber is not only justified but also optimal are long distances, increased requirements for channel capacity and an “aggressive” electromagnetic environment.
The next question that needs to be answered is: “Which fiber (multimode or singlemode) is better to use?” The selection criterion here is the transmission distance. Multimode fiber can be used for short distances (up to 4 km). The type (multimode/singlemode) of fiber does not affect the quality of video signal transmission, but the price of multimode equipment is somewhat lower today.
Analog or digital?
Transmission of video signals via fiber optic cable is basically no different from transmission of other signals. The only difference is that not all signals can be digitized.
The main differences between analog and digital video signal transmission were discussed in more detail in the TZ (No. 1, 2 — 2010). Most of the advantages of using fiber optics (transmission distance, large number of channels) are manifested precisely when using digital equipment. For high-quality video image transmission, the bandwidth and bit depth of the analog-to-digital conversion are of great importance. When choosing equipment, these parameters should also be taken into account (for devices used in CCTV, the standard is a bandwidth of 5-10 MHz and 8-10-bit analog-to-digital conversion). That is, if the funds allocated for the installation of the video surveillance system allow, it is better to use digital equipment.
Another question frequently asked by CCTV installers who are using fiber-optic communication lines for the first time is: «How does this or that multiplexing method affect the quality of the transmitted video signal? Does the fact that a large number of different signals will be transmitted over one fiber affect the image quality?» The basic concepts of channel multiplexing used in fiber-optic transmission (WDM and CWDM) were generally discussed in previous issues of the magazine. The short answer is as follows: neither the multiplexing method nor the number of transmitted signals (including the presence of additional audio channels, telemetry transmission, etc.) have any effect on the quality of the video image. And, whatever the device is — a simple video signal receiver and transmitter, a trunk or multi-channel (transmitting more than a hundred video, telephony, control signals, etc.), the image quality will be the same if the digitization parameters match.
As we can see, there are significantly more advantages than disadvantages when using fiber-optic communication lines to transmit video.
The main factors holding back the widespread use of fiber-optic communication lines for video transmission are still the relatively high cost of equipment and the increased requirements for the qualifications of installers.
4-channel digital video transmitter/receiver FS14SVT/FS14SVR
The products are designed to transmit 4 video channels over one single-mode optical fiber in real time, using 8/10-bit digital encoding/decoding at a laser wavelength of 1310 nm, high quality at a distance of up to 50 km. The video channel has lightning protection at the input. The devices do not require adjustment or configuration before starting work. The digital transmission method ensures stable operation for a long time in any external conditions. The optical budget is 21 dB, and the power consumption is 8 W. The 220 V power supply has built-in protection against voltage drops. The products are available both in a flat case with an external power supply, and for installation in a 19 «rack. A power transformer and one or two boards are installed inside. As a rule, receivers are mounted in a rack (transmitters are located near the cameras on the street), up to 80 four-channel receivers can be mounted in one full 40U rack. The performance characteristics allow the use of devices in various temperature conditions, from -45 C to +70 C. These models are mainly used in video surveillance systems for transmitting video and control signals from PTZ cameras to control rooms over long distances.
A series of fiber optic modems for specialized applications — ASFOM (KBC Networks)
The ASFOM series combines analog video, data, contact closure, telephone and Ethernet channels in the quantity and order required for a given site. Solutions can be as simple as a single contact closure channel or as large as 128 real-time video signals, all on a single monofiber.
The flexibility of the ASFOM series devices allows them to be used in areas such as security and video surveillance, access control, building and industrial process control and many others, and to meet almost any requirement without the need for non-standard or custom-made devices. The ASFOM series devices are characterized by increased protection against environmental influences and can be used at temperatures from -40°C to +70°C.
32-channel multiplexers with 8 channels for bidirectional data transmission ComNet™ FVT/FVR320D8 (ComNet)
FVT/FVR320D8 multiplexers (receiver/transmitter) combine 32 separate video channels and 8 data channels (RS232/422/485-2W & 4W) into one high-speed stream for bidirectional transmission, and all information is transmitted over one fiber-optic communication line at a distance of up to 54 km. These devices are used to transmit/receive broadcast-quality video signals with 10-bit digital encoding. ComNet multiplexers have a lifetime manufacturer's warranty and operate reliably in the temperature range from -40 to +75º C.
The plug-and-play design ensures easy installation of the FVT/FVR320D8 without the need for additional optical or electrical adjustments, and LED indicators on the device housings allow you to monitor the current status of the receivers/transmitters. The exemplary quality of the transmitted video allows us to recommend ComNet multiplexers for use in high-performance CCTV systems.
VT/VR14100 Series (IFS/UTC FIBER & TRANSMISSION)
The VT/VR14100 Series of video transmitters and receivers from IFS/UTC Fiber & Transmission utilize the latest 10-bit analog-to-digital conversion technology to deliver true broadcast-quality video that exceeds EIA RS-250C short-haul signal quality requirements. These ruggedized modules deliver video over a single single-mode or multimode fiber for distances up to 108 km, making them ideal for unprepared roadway or field applications (-40C to +74C). Due to the very high quality of video transmission, the VT/VR14100 series modules (including VT/VR14120, VT/VR14130) are ideal for networks involving several physical transmission layers where video signal degradation may be a problem, such as frequency-division multiplexing or digital multiplexing links, T-1 or fractional T-1 codecs and SONET or ATM trunk lines. These units are completely transparent and fully compatible with any NTSC, PAL or SECAM stand-alone TV camera. The plug-and-play design ensures easy installation without the need for electrical or optical alignment. LED indicators are provided for quick assessment of the system status. Works with ST-type connectors.
CFO-321 System
The CFO-321 system allows for the transmission of high-quality analog video signals using digital coding. The transmitted signal also carries information about the data and status of alarm inputs. Transmission is carried out via multimode fiber over a distance of up to 8 km.
Single-channel devices occupy 1 slot and can be installed either separately in a special housing or in a standard crate. There is also a compact transmitter model.
To simplify the design of large systems, each CFO-321 module supports the main data transmission protocols, which are selected using special DIP switches.
ComNet™ FVT/FVR1031 (ComNet) Transceivers
The FVT/FVR1031 series of fiber optic receivers/transmitters provide reception and transmission of television signals over single- or multi-mode fiber with 10-bit digital coding, as well as bidirectional data transmission and transmission of commands received over a coaxial cable. FVT/FVR1031 are compatible with most video cameras from leading global manufacturers and support the following interfaces: RS-232, RS-422 and 2- or 4-wire RS-485, as well as all major data transmission protocols.
The plug-and-play design allows for easy installation of the equipment without the need for optical or electrical adjustment, and the FVT/FVR1031 LED indicators provide monitoring of their current status. The transmission range of these devices reaches 70 km, and the operating temperature range is from -40 to +75°C. At the same time, ComNet receivers and transmitters are produced as stand-alone devices and for rack mounting, and have a lifetime manufacturer's warranty.
SF80S2T-N transmitter and SF80S2R-N receiver of video signals over fiber optic cable (SF&T)
The devices provide transmission of 8 video signals over a distance of up to 40 km via single-mode optical fiber of the 9/125 µm standard using high-quality 10-bit analog-to-digital conversion. Compatible with any CCTV cameras of NTSC, PAL or SECAM systems.
The devices have a wide optical range, optical attenuators are not required. Multiplex transmission in real time, plug-and-play support, hot-swappable modules. Bandwidth: 5 Hz…10 MHz.
The equipment does not require additional settings, can be used as separate modules and installed in a rack. LED indication for monitoring the operation of devices. Built-in lightning protection. Operating temperature from -40 ° C to +70 ° C. 3-year warranty.
SVP-11T/12R
SVP-13T/14R («Special Video Project»)
The devices are designed to transmit signals in television surveillance systems over distances of up to 6–12 km. The transmitter and receiver sets transmit one composite video signal over a multimode optical cable at a wavelength of 850 and 1310 nm.
Video signal resolution is 570 TVL, signal-to-noise ratio at maximum range is no worse than 50 dB, frequency band: 50 Hz – 8 MHz. The automatic gain control system constantly maintains a video signal amplitude of 1 V at the output. Light signaling indicates the presence or absence of a video signal. The devices are small in size, have low power consumption, and are equipped with wall mounting elements.
The devices are protected against power supply reversal – they do not fail if connected incorrectly. They operate in plug and play mode – no setup or adjustment is required during installation.
The signal receivers are also available in a housing designed for installation in standard 19” racks.