With the rapid advancement of Safe City, more and more optical fiber technology is used to transmit images, sounds, data and other information in the security monitoring project. The key equipment of the optical fiber transmission system, the digital video optical transceiver, is favored by the majority of users.
Optical transceiver troubleshooting method
First, there is no video signal 1. Check whether the power supply of each device is normal.
2. Check if the video indicator of the corresponding channel on the receiving end is lit.
A: If the indicator light is on (the light is on to prove that the channel has a video signal output at this time). Then check whether the video cable between the receiving end and the terminal device such as the monitor or DVR is connected, whether the video interface connection is loose or there is a virtual soldering.
B: The video indicator on the receiving end is not lit. Check whether the video indicator of the corresponding channel on the front end is lit. (Recommended to re-power the optical receiver to ensure the synchronization of the video signal)
a: The light is on (the light is on, indicating that the video signal collected by the camera has been sent to the front end of the optical transceiver), check whether the optical cable is connected, and whether the optical interface of the optical transceiver and the optical cable terminal box are loose. It is recommended to re-plug the fiber interface once (if the tail fiber is too dirty, it is recommended to wash it with cotton alcohol before inserting it).
b: The light is off, check if the camera is working properly, and the video cable from the camera to the front transmitter is connected reliably. Whether the video interface is loose or there is a virtual soldering.
If the above method cannot eliminate the fault and has the same type of equipment, you can use the replacement check method (requires the equipment to be interchangeable), that is, the fiber can be accurately connected to the receiver at the other end or the remote transmitter can be accurately judged. Faulty device.
Second, the screen appears to interfere with snowflakes
This situation is mostly caused by excessive attenuation of the fiber link or excessive length of the front-end video cable subject to AC electromagnetic interference.
1. Check if the pigtail has excessive bending (especially when multi-mode transmission should be carried out, do not bend the pigtail too much).
2. Check whether the connection between the optical port and the terminal box flange is connected to the reliable flange core or not.
3. Whether the optical port and the pigtail are too dirty, use alcohol and cotton to clean and then insert.
4. When laying the line, the video transmission cable should use 75-5 cable with good shielding quality and good transmission quality, and should avoid AC lines and other objects that are likely to cause electromagnetic interference.
There is no control signal or the control signal is not normal.
Check that the optical transceiver data signal indicator is correct.
a: Check whether the data cable is connected correctly and securely according to the data port definition of the product manual. In particular, the positive and negative poles of the control line are reversed.
Check whether the control data signal format issued by the control device (computer, keyboard or DVR, etc.) is consistent with the data format supported by the optical transceiver (for details on the data communication format, see page ** of this manual). Is the baud rate higher than that supported by the optical transceiver? Range (0-100Kbps).
b: Check whether the data cable is connected correctly and securely according to the data port definition of the product manual. In particular, whether the positive and negative poles of the control line are reversed.
Optical fiber machine common fault solution 1. Optical path problem of optical transceiver:
In the security monitoring project, most of the optical cables are laid by the users themselves, generally G652 single-mode optical fibers. Since the coverage of the system is generally small, the optical link loss of the device is very rich with the standard (≤20KM). Therefore, the optical transceiver does not have excessive requirements for optical path loss, but users often encounter no image, image jitter, and image quality. Problems such as poor, when most of the problems are on the pigtails, jumpers or adapters at both ends of the light path, and rarely related to the trunk light path. Common problems are: 1. The fiber optic connector is not inserted correctly; 2. The fiber optic connector core (ceramic tube) is contaminated. The solution is:
1. Re-insert the active connector or replace the fiber jumper; 2. Wipe the plug with 99, 9% absolute ethanol, and the core of the socket; 3. Check the video cable of the camera with a multimeter to determine whether there is a video signal.
2. Data interface of optical transceiver:
In order to meet the needs of security monitoring, all kinds of equipment (matrix, hard record, decoder) provide RS-485 data interface. The advantage of this format data interface is long transmission distance, strong load capacity and can form four. Line full-duplex communication bus, any two devices on the line can achieve two-way communication, while the four-wire RS-422 bus can only achieve two-way communication between the master and slave, but not between the slaves. Its shortcoming is that there is an enabling end, which is in a three-state form, which brings instability and even "catch" to the communication. If there is no communication (out of control), you should look up the reasons from the following aspects:
1. Detect whether there is any control signal. Use the multimeter AC 10V test controller (matrix, hard record, etc.) to output the RS-485 port to see if it has control signal output.
2. Determine whether the RS-485 interface of the optical transceiver is normal. If the UA-B voltage is zero, it is considered abnormal.
Yuntai chaos can not be controlled, this phenomenon is caused by two reasons: a) RS-485 port A +, B- reverse; b) system impedance is seriously mismatched.
3. Switching quantity of optical transceiver
The switch signal is a TTL level pulse train, which can control the operation of warning lights, alarm bells, relays, etc. The load capacity of the switch interface is measured by the magnitude of the controlled current. For example, the switching capacity of the EW series optical transceiver is ≤ 1, 5A.
1. The EW series optical transceiver switch interface supports the normally open button, but when the following figure is connected, the normally open and normally closed forms are supported:
2. The switch quantity interface cannot be directly used in parallel. If necessary, it can only be accessed through the distribution circuit.
3. Some customers use the RS-485 bus to transmit the switch quantity. According to our practical experience, this method is not advisable. It often occurs when the work is working for a period of time (such as 3~4 days). Defects in the switching of RS-485 converters may be the problem.
4. Harm of transient interference of optical transceivers and countermeasures
1. Generation of transient interference: Transient interference is generated by large inductive loads, such as switching of motors, transformers, relays, etc., and during the occurrence of lightning, it often invades the optical transceiver by electrostatic induction.
2, the hazard of transient interference: due to its high frequency of interference, short duration, large amplitude of interference (hundreds of thousands of volts), it can burn out the key parts of the RS-485 interface chip and main chip of the optical transceiver, but does not stay Traces, especially during the summer thunderstorm season, have a great impact on the destructive power, making users, businesses and manufacturers very nerve-wracking.
3. Countermeasures: Although optical transceiver manufacturers use various protection methods such as bypass (self-recovery diode), absorption (bidirectional suppression diode, etc.), isolation (optocoupler isolation), they cannot completely eliminate transients. The damage caused by interference, the RS-485 interface is damaged frequently, causing great pressure on users and manufacturers.
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