Technical application: installation, lightning protection and maintenance of optical transceivers

With the gradual deepening of applications, domestic manufacturers have gradually started to independently research and develop optical transceiver products. The emergence of domestically produced products has greatly reduced the cost of the entire optical transceiver. At this time, single-mode optical cables and optical transceivers have gradually matured, making the transmission distance farther. The effect is better, and it has been applied in more monitoring fields. When installing and debugging the optical transceiver, the optical transceiver should be well protected against the site, moisture, water and dust. At the same time, pay attention to the actual operation of the site, and it must be equipped with suitable fiber. Fibers with defective faults cannot be used. If they do not match, the transmission quality of the optical transceiver will be seriously affected. When the optical cable is welded, the optical attenuation or loss of the optical cable should be measured within the effective value range. The debugging of the optical transceiver is mainly for the debugging of the optical fiber and the data channel. Due to the variety of optical transceiver data, according to the actual needs of the site, the data type of the optical transceiver used in the field is not the same. When debugging, be sure to refer to the corresponding manual, according to the data dialing and interface definition on the manual. Data wiring. The environment where the optical transceiver is installed on site is complicated. Some users usually suspect that the product is faulty when debugging fails. In fact, the optical fiber product technology is very mature. The product has been repeatedly tested and copied before leaving the factory, so the product itself is less likely to be problematic. Therefore, when there is a problem in the field, the first thing to consider is the installation problem. You can check the following aspects: • The fiber itself has not been tested, the optical path is unreachable or unstable or the optical attenuation is too large, etc. • The front-end equipment is faulty, such as The camera has no video or no power supply; • The back-end equipment is faulty, such as no video on the monitor, the keyboard control protocol is wrong, and it cannot be controlled by itself; • The connection line is faulty, such as the soldering of the video head is not good, the control line is wrong, or The cable is connected incorrectly, reversed, etc. The above phenomenon is especially the most likely to occur when a line fault occurs, and it needs to be carefully checked when encountering a problem. When troubleshooting, you can use the exclusion method, one device and one device to eliminate, and finally accurately determine the key problem. When judging whether there is any problem with the optical transceiver, it is recommended that the user put the transmitter and the receiver together for close-range testing. If it is still not available, the optical transceiver itself is faulty, and it is necessary to contact the manufacturer for replacement. In order to reduce the problem, the user can test the optical transceiver at a close distance before installation as much as possible, so that the installation and debugging can be quickly completed, thereby saving the construction period. Optical terminal lightning protection method Optical transceivers, especially as front-end equipment transmitters, are usually installed in outdoor equipment boxes. The site environment is quite harsh, and lightning protection is extremely important. The advantages and disadvantages of lightning protection measures directly determine the probability of optical transceiver failure. The damage modes of lightning are mainly divided into three types: direct lightning strike, inductive lightning and ground potential counterattack. The most serious impact on optical transceivers is ground potential counterattack. The so-called ground potential counterattack is when the lightning arrester and other lightning receptors will directly strike the thunder. When the lightning current is discharged to the earth through the down conductor and the grounding body, a relatively high moment will occur on the down conductor, the grounding body and the metal object connected thereto. Voltage, this high voltage creates a huge potential difference between electronic objects such as metal objects and cables that are close to them but not in direct contact. The electric shock caused by this potential difference is the ground potential counterattack. The ground potential counterattack is to damage the optical transceiver by the following form: When the lightning current leaks into the earth, the ground potential of the grounding grid will be raised to tens of thousands or hundreds of thousands of volts within a few microseconds. Highly destructive lightning currents will flow from the grounded parts of various equipment to these devices, or by penetrating the ground insulation to other nearby equipment, resulting in damage or damage to the equipment. The damaged parts are mainly: PCB board of the chassis power supply. Chips on electronic components, video interface chips and their related electronic components, audio and data ports. Although the form of lightning damage is varied, it is still possible to reduce the probability of optical transceiver failure by taking scientific protective measures. First of all, ensuring that the grounding device works well is a prerequisite for lightning protection measures, because all induced currents are finally leaked into the earth. In general, the smaller the grounding resistance, the better the leakage effect. It is usually better to control the grounding resistance within 4 ohms. The grounding resistance can be measured using a grounding clamp. For some areas with high soil resistivity, consider adding a drag reducer to the soil to reduce the grounding resistance. Secondly, the front-end equipment should be equipped with a surge protector. When the voltage is normal, the surge protector is in a high-impedance state. There is only a small leakage current, and the power loss is small. When an overvoltage occurs in the line, the surge protector is In the low-resistance state, the over-voltage flows into the earth through the surge protector in the form of discharge current, and the over-voltage is suppressed. When the line voltage returns to normal after the surge voltage is over, the surge protector is in a high-resistance insulation state, so the surge The protector must have a good grounding device to match it. The video signal output port of the front camera and the video input port of the transmitter are connected to the surge protector. If the transmitter is connected with other data lines, the data lightning protection device needs to be installed at the beginning and end of the control signal line. Lightning protection devices such as power supply lightning arresters are also added to the power input terminals of the camera and the optical transceiver. When installing the lightning protection device, make sure that the lightning protection device is close to the inlet. If the lightning protection device is too far away from the video port and the data port, it will not play the lightning protection effect. After adding the lightning protection equipment, the rest is the design problem of the grounding grid. The grounding pile must be in place to ensure good grounding of the optical transceiver. A good low-impedance grounding grid design can ensure that the lightning protection equipment in the system works well and can effectively balance the voltage of all parts in the whole transmission system to prevent the ground potential difference from being in the line. The interference of the equipment can also effectively avoid the damage of the ground potential counterattack to the equipment. Daily maintenance of optical transceivers Normally, the working environment of optical transceivers is quite harsh. Pay attention to keeping the optical fiber head clean when using. The optical transceiver is very sensitive to dust. Because the optical transceiver is in the process of transportation or after the customer uses it for a period of time, it may cause clogging due to dust or debris at the optical fiber port, thus affecting the normal transmission of video and data. Water alcohol and dust-free paper clean the fiber tip to avoid sticking dust. The fiber jumper inside the optical transceiver is connected to the external fiber through an adapter. Usually the adapter is a ceramic die. Pay special attention when inserting and removing the fiber tip. Do not use force to prevent the ceramic sleeve from being crushed or crushed. The optical transceiver cannot transmit signals properly.

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Sept.30, 2019