Views:0 Author:Site Editor Publish Time: 2021-09-22 Origin:Site
CATV optical transmitters convert CATV signals into optical signals and coupling digital TV optical signals into optical fibers. The laser is the light source of the CATV optical transmitter. At present, the distributed feedback semiconductor laser (DFB) and YAG solid state laser (YAG laser) are commonly used in CATV systems. The output power of the laser varies with the change of the driving current (within a certain range). Because the RF TV signal is a wide-band analog signal, the performance requirements of the laser are very strict, especially the electro-optical transformation non-linearity, relative strength noise, etc. Now let's take a look at how CATV optical transmitters are used.
Correct selection of RF signal input level.
Read the CATV optical transmitter manual carefully before using it. CATV optical transmitter housing should be well grounded before power. To ensure that the CATV optical transmitter has a continuous and uninterrupted, stable voltage of the normal power supply. The laser assembly and photoelectric conversion module of CATV optical transmitter should avoid the impact of instantaneous pulse current. Therefore, in use must avoid or reduce frequent switching machine, in order to ensure the life of the laser. Once the laser enters the working state, the human eye must not look directly at the light output port on the rear panel of the CATV optical transmitter, so as not to burn out the laser retina.
The RF drive level of DFB optical transmitter directly determines the modulation system of the CATV optical transmitter, and also determines the value of C/N, CTB and CSO. If the RF level added to the CATV optical transmitter is too large, the M value of the optical modulation system will increase, which will degrade the nonlinear indexes of CTB and CSO. It will also cause the over-drive of the DFB laser, which will lead to the decline of the output power of the CATV optical transmitter. The input level is too small, so that the light modulation system is reduced, resulting in the noise ratio index of the CATV optical transmitter can not meet the demand. Therefore, the correct selection of RF driving level is the key to ensure the indicators of optical fiber transmission network. CATV optical transmitters produced by different manufacturers require different RF drive levels, so the input RF level of the transmitter should be set according to the manufacturer's product manual.
When installing the light movable joint, first wipe the output port and connection plug of the light transmitter with an alcohol cotton ball, then align the protruding edge of the optical fiber plug with the gap of the light output port, screw it to the end, not too tight nor too loose, ensure that the two plugs are aligned and have good contact. After the power is switched on and the laser enters the normal working state, press the TEST button on the front panel to look at the LCD display and check the work-related state of the laser in sequence.
Set up technical data files, file all technical data during network construction, such as product specification, design scheme, optical cable trunk line trend diagram, loss of each optical fiber (optical joint fusion loss, movable joint loss), total loss of link, measured input power of each light point, etc. As the basis of judging whether the CATV optical transmitter is normal in the future.