Video surveillance system using fiber optic cable instead of the coaxial cable could increase the long distance transmission of high quality, strong conditions. The transmission characteristics and versatility of coaxial cable is unmatched. Advanced transmission, stable performance, high reliability and versatility of the information exchange network can also lay good foundation for future information superhighway;
(A) The advantages and disadvantages of optical transmission
1. Long transmission distance, now single-mode fiber optic attenuation per kilometer could be 0.2dB~0.4dB which is the loss of 1% of coaxial cable per kilometer.
2. Transmission capacity, via an optical fiber can transmit more than dozens of road signals. If using a multicore cable capacity, then the capacity growths. In this way, several fibers fully meet the considerable demands on transmission capacity for a long time.
3. The transmission of high quality: Unlike coaxial cable, optical fiber transmission does not require considerable relay amplifier, eliminating the noise and distortion of nonlinear superposition.
4. Anti-jamming performance: Optical fiber transmission is not subject to electromagnetic interference, suitable for application to strong electromagnetic interference and electromagnetic radiation in the environment.
5. The main disadvantage is the high cost and construction difficult.
(B) The selection of single or multimode fiber optical transceiver
1. Currently common fibers by mode points has two large class: more die fiber and single-mode fiber more die cable for video image transmission Shi, only meet most far 3~5km around of transmission distance, and on video light end machine of bandwidth (for simulation modulation) and transmission rate (for digital type) has larger of limit, General applies Yu short from, and small capacity, and simple application of occasions. Single-mode fiber optic cable because of excellent features and low price has become the mainstream of optical communication, but its higher equipment prices than multimode optical transceiver.
2. Video optical transmitter and receiver technologies are divided into analog modulation optical transmitter and receiver and digital optical transmitter and receiver for two broad categories of non-compression encoding. Analog optical transceiver uses the baseband video signal (referred to as AM) or pulse-frequency modulation (PFM) technology. Digital optical transmitter mainly refers to compression encode video optical transceiver, strict sense, is a video optical transceiver with digital transmission, still is a standard analog video input and output signals. Simulation of optical transceiver development has been more than ten years of history, is already a mature product, stability and maintainability, said analog device at temperature drift, aging characteristic and long-term stability is obviously not as good as a digital device. Price alone, said current simulation in the 1~2-channel video optical transceiver price still has its advantages, but on the more than 4-channel video optical transceiver difference between analog and digital has almost gone, if required ...