Coaxial cable transmission characteristics
Security market has always been no lack of "war" front-end analog surveillance cameras with HD PK war continues, but the back-end NVR and DVR do not know when joined the smoke-free war. More surprising is that even the two transmission also expressed their "stand" behind his teammates. Simulation and high-definition monitor corresponding coaxial cable and optical fiber transmission, this is still a never ending fight.
In the video transmission system, the output impedance of the camera 75 in the CCTV video signal transmission engineering major with an insulating layer of solid polyethylene SYV coaxial cable, and the insulating layer is a polyethylene foam SBYFV coaxial cable. These two are the characteristic impedance of the cable 75, in terms of the amount of attenuation which is also smaller than the former.
HD PK war simulation and coaxial cable and fiber optic transmission of
Faced with the general monitoring requirements, best 75-5 coaxial cable transmission distance of about 300 meters, if required to meet more long-distance transmission, you need to increase the video amplifier to prevent signal attenuation. Coaxial video cable video signal transmission, high-frequency part of the decay faster; amplifier can be corrected to compensate by adding a cable compensation unit allows the transmission line extension 500m.
As a traditional analog and digital high-definition monitor to monitor the transmission medium, coaxial cable transmission has the following four characteristics:
First, the simple wiring. The system can be implemented in practical applications 40-channel monitoring signal through a coaxial cable two-way transmission. Data transmission, including both video information, including audio and control signal information.
Second, the large frequency bandwidth. And network monitoring is different, coaxial cable frequency bandwidth of 0 ~ 1000MHz, its large bandwidth monitoring data uses only some of the bandwidth resources, as well as alarm and other information transmission space left.
Coaxial Cable Applications
Three: bidirectional transmission: the use of 5 ~ 65MHz to downstream transmission and front-end PTZ camera control data signal, use 110 ~ 550MHz uplink transmission to monitor video and audio signals, and a signal 65 ~ 87MHz bidirectional transmission buffer zone, up and down signal transmission lines will not conflict prevails.
Four: interference: the audio, video and control signals to the high-frequency design, only attenuate the carrier signal transmission without attenuation of the video signal.
Four features of optical fiber transmission
And coaxial cable corresponding to an optical fiber transmission, optical transmission biggest advantage lies in the distance. If the coaxial cable transmission to maintain the best results within 300 meters, an increase of signal amplifier will increase the complexity of the system and reduces the reliability of the system. This is the biggest question raised by coaxial cable to fiber.
And 300m are different, not only to achieve optical fiber transmission distance transmission, coaxial cable attenuation is only one percent loss per kilometer, and therefore can be achieved without relay transmission 20km. Optical fiber can transmit analog images, digital images can also be transmitted, an optical fiber can also transmit audio and video information and the signal control information.
Fiber need of special protection
Optical fiber transmission also has four characteristics
First: a wide frequency band. Fiber bandwidth has reached 1.0GHz, far higher than the bandwidth of coaxial cable can also be multiplexed video information.
Second: attenuation. As I said above, the optical fiber transmission attenuation is much smaller than coaxial cable. Cost also higher than coaxial cable lot.
Third: immunity to interference. Coaxial cable is also have a certain immunity, but the fiber perform better. Not as a result of a short circuit, poor contact or cable aging phenomenon caused by sparks or static electricity like a traditional coaxial cable and communication cable, so it is suitable for long-distance transmission of information and the requirements of high-security applications.
Optical signal test: optical fiber transmission
Fourth: transmission confidentiality. Optical fiber transmission confidentiality is highly secure communications medium, no doubt.
Coaxial cable and fiber optic contrast, exactly what kind of transmission is better, from the application development trend, "Light of Copper" can explain everything. It is noteworthy that the optical fiber is relatively fragile, the wiring should be careful, but based on the transmission distance, transmission effect, fiber still has great value in the development of surveillance.