Problems and solutions encountered in the installation and use of optical fiber transceivers
The first step: first see whether the indicator light of the optical fiber transceiver or optical module and the twisted pair port indicator light are on?
1. If the optical port (FX) indicator of the A transceiver is on and the optical port (FX) indicator of the B transceiver is not on, the fault is on the A transceiver side: one possibility is: A transceiver (TX) optical transmission The port is bad because the optical port (RX) of the B transceiver does not receive the optical signal; another possibility is: there is a problem with this fiber link of the optical transmit port of the A transceiver (TX), such as a broken optical jumper .
2. If the FX indicator of the transceiver is off, please make sure whether the fiber link is cross-linked? One end of the fiber jumper is connected in parallel mode; the other end is connected in cross mode.
3. The twisted pair (TP) indicator is off, please make sure the twisted pair connection is wrong or the connection is wrong? Please use a continuity tester to detect (however, the twisted pair indicator of some transceivers must wait for the optical fiber chain Lights up after the road is connected).
4. Some transceivers have two RJ45 ports: (ToHUB) indicates that the connection line to the switch is a straight-through line; (ToNode) indicates that the connection line to the switch is a crossover line.
5. Some hair generators have an MPR switch on the side: it means that the connection line to the switch is a straight-through method; DTE switch: the connection line to the switch is a cross-over method.
Step 2: Analyze and judge whether there is a problem with fiber jumpers and fiber optic cables?
1. On-off detection of optical fiber connection: use laser flashlight, sunlight, etc. to illuminate one end of the fiber jumper; see if there is visible light on the other end? If there is visible light, it indicates that the fiber jumper is not broken.
2. Detection of optical cable connection and disconnection: use laser flashlight, sunlight, luminous body to illuminate one end of the optical cable connector or coupler; see if there is visible light at the other end? If there is visible light, it indicates that the optical cable is not broken.
Step 3: Is the half / full duplex method wrong?
Some transceivers have FDX switches on the side: full duplex; HDX switches: half duplex.
Step 4: Test with optical power meter
The luminous power of the optical fiber transceiver or optical module under normal conditions: multimode: between -10db–18db; single-mode 20 km: between -8db–15db; single-mode 60 km: between -5db–12db ; If the luminous power of the optical fiber transceiver is between: -30db–45db, then it can be judged that there is a problem with this transceiver
Matters needing attention of optical fiber transceiver
For the sake of simplicity, it is better to use a question and answer style, which can be seen at a glance.
1. Does the optical transceiver itself support full-duplex and half-duplex?
Some chips on the market can only use the full-duplex environment at present, and cannot support half-duplex. For example, if they are connected to other brands of switches (SWITCH) or hub sets (HUB), and it uses half-duplex mode, it will definitely cause Serious conflicts and packet loss.
2. Have you tested connection with other fiber transceivers?
At present, there are more and more fiber optic transceivers on the market. If the compatibility of transceivers of different brands is not tested beforehand, it will also cause packet loss, long transmission time, and fast and slow.
3. Is there a safety device to prevent packet loss?
In order to reduce costs, some manufacturers use a register data transmission mode to reduce costs. The biggest disadvantage of this method is that the transmission is unstable and packet loss. The best is to use a buffer line design, which is safe Avoid data packet loss.
4. Temperature adaptability?
The optical fiber transceiver itself will generate high heat when it is used. When the temperature is too high (not greater than 50 ° C), whether the optical fiber transceiver is working properly is a factor worthy of customer consideration!
5. Does it meet the IEEE802.3u standard?
If the optical fiber transceiver complies with the IEEE802.3 standard, that is, the delaytime is controlled at 46bit, if it exceeds 46bit, it means that the transmission distance of the optical fiber transceiver will be shortened.
Summary and solutions of common fault problems of fiber optic transceivers
There are many types of fiber optic transceivers, but the method of fault diagnosis is basically the same. In summary, the faults that occur in fiber optic transceivers are as follows:
1. The Power light is off, the power supply is faulty;
2. The Link light is off, and the fault may be as follows:
a. Check whether the optical fiber line is broken
b. Check whether the fiber line loss is too large and exceeds the receiving range of the equipment
c. Check whether the fiber interface is connected correctly, the local TX is connected to the remote RX, and the remote TX is connected to the local RX.
d. Check whether the optical fiber connector is inserted into the device interface intact, whether the jumper type matches the device interface, whether the device type matches the optical fiber, and whether the transmission length of the device matches the distance.
3. The circuit Link light is off, and the fault may be as follows:
a. Check if the network cable is broken;
b. Check whether the connection type matches: network cards and routers use cross-over cables, and switches, hubs and other devices use straight-through cables;
c. Check whether the transmission rate of the device matches;
4. Network packet loss is serious, and the possible failures are as follows:
a. The electrical port of the transceiver does not match the network device interface, or the duplex mode of the device interface at both ends.
b. If there is a problem with the twisted pair and the RJ-45 head, check
c. Optical fiber connection problem, whether the jumper is aligned with the device interface, and whether the pigtail matches the type of the jumper and coupler.
5. After the fiber transceiver is connected, the two ends cannot communicate
a The optical fiber is reversed, and the optical fibers connected to TX and RX are swapped
b. The RJ45 interface is not properly connected to the external device (note the straight-through and splicing)
The optical fiber interface (ceramic ferrule) does not match. This fault is mainly manifested in the 100M transceiver with photoelectric mutual control function. The photoelectric mutual control transceiver has no effect.
6. On-off phenomenon
a. It may be that the attenuation of the optical path is too large. At this time, the optical power of the receiving end can be measured with an optical power meter. If it is near the receiving sensitivity range, it can basically be judged as an optical path failure within the range of 1-2dB
b. The switch connected to the transceiver may be faulty. At this time, the switch is replaced with a PC, that is, the two transceivers are directly connected to the PC, and the two ends are paired with PING.
c. The transceiver may be faulty. At this time, connect the two ends of the transceiver to the PC (do not pass through the switch). After the two ends have no problem with PING, transfer a larger file (100M) from one end to the other end. Observe its Speed, if the speed is very slow (more than 15 minutes for the file transfer below 200M), it can basically be judged as a transceiver failure.
d. Communication crashes after a period of time, that is, communication fails, and it returns to normal after restarting.
This phenomenon is generally caused by the switch. The switch will perform CRC error detection and length check on all received data, and check that the wrong packet will be discarded, and the correct packet will be forwarded.However, some packets with errors in this process cannot be detected in the CRC error detection and length check. Such packets will not be sent out or discarded during the forwarding process, and they will accumulate in the dynamic cache. In (buffer), it can never be sent out. When the buffer is full, it will cause the switch to crash. Because restarting the transceiver or restarting the switch at this time can restore communication to normal, users usually think that it is the transceiver’s problem.
8. Transceiver test method
If you find that there is a problem with the transceiver connection, please test according to the following methods to find out the cause of the failure
a. Near-end test:
Computers at both ends can ping, if it can be pinged, it proves that there is no problem with the fiber optic transceiver. If the near-end test fails to communicate, it can be judged as a fiber transceiver failure.
b Remote test:
Computers at both ends are paired to PING. If PING is unavailable, you must check whether the optical path connection is normal and whether the transmit and receive power of the optical fiber transceiver is within the allowable range. If it can be pinged, it proves that the optical connection is normal. It can be judged that the fault is on the switch.
c. Remote test to determine the fault point:
First connect one end to the switch and the two ends to PING. If there is no fault, it can be judged as the fault of the other switch.
Common fault problems are analyzed below through question and answer
According to the daily maintenance and user problems, I will summarize them one by one in the form of question and answer, hoping to bring some help to the maintenance staff, to determine the cause of the fault according to the fault phenomenon, pinpoint the fault point, and “correct the medicine”.
1. Q: What kind of connection is used when the transceiver RJ45 port is connected to other equipment?
Answer: The RJ45 port of the transceiver is connected to the PC network card (DTE data terminal equipment) using cross-twisted pair, and connected to HUB or SWITCH (DCE data communication equipment) using parallel twisted pair.
2. Q: What is the reason why the TxLink light is off?
Answer: 1. The wrong twisted pair is connected; 2. The twisted pair crystal head is not in good contact with the device or the quality of the twisted pair itself; 3. The device is not properly connected.
3. Q: What is the reason why the TxLink light does not blink but stays on after the fiber is connected normally?
Answer: 1. The transmission distance is usually too long; 2. Compatibility with the network card (connected to the PC).
4. Q: What is the reason why the FxLink light is off?
The fiber cable is connected incorrectly, the correct connection method is TX-RX, RX-TX, or the fiber mode is wrong;
The transmission distance is too long or the intermediate loss is too large, exceeding the nominal loss of this product. The solution is to take measures to reduce the intermediate loss or replace it with a longer transmission distance transceiver.
The operating temperature of the optical fiber transceiver is too high.
5. Q: What is the reason why the FxLink light does not blink but stays on after the fiber is connected normally?
Answer: This fault is generally caused by the transmission distance being too long or the intermediate loss too large, exceeding the nominal loss of this product. The solution is to minimize the intermediate loss or replace it with a longer transmission distance transceiver.
6. Q: What should I do if the five lights are all on or the indicator is normal but unable to transmit?
Answer: Normally, you can turn off the power and restart to normal.
7. Q: What is the ambient temperature of the transceiver?
Answer: The optical fiber module is greatly affected by the ambient temperature. Although it has a built-in automatic gain circuit, after the temperature exceeds a certain range, the transmitted optical power of the optical module is affected and reduced, thereby weakening the quality of the optical network signal and causing packet loss The rate rises, even disconnecting the optical link; (generally the operating temperature of the optical fiber module can reach 70 ℃). which exceeds the upper limit of the frame length of the optical transceiver and is discarded by it, reflecting the high or unsuccessful packet loss rate.
The maximum transmission unit, the general IP packet overhead is 18 bytes, and the MTU is 1500 bytes; now high-end communication equipment manufacturers have internal network protocols, generally using a separate packet method, will increase the IP packet overhead, if the data is 1500 words After the IP packet, the size of the IP packet will exceed 18 and be discarded), so that the size of the packet transmitted on the line meets the network device’s limit on the frame length. 1522 bytes of packets are added VLANtag.
9. Q: After the chassis has been working for a period of time, why do some cards fail to work properly?
Answer: The early chassis power supply adopts the relay mode. Insufficient power supply margin and large line loss are the main problems. After the chassis has been working for a period of time, some cards cannot work normally. When some cards are pulled out, the remaining cards work normally. After the chassis has been working for a long time, the connector oxidation causes a large connector loss. This power supply falls beyond the regulations. The required range may cause the chassis card to be abnormal. High-power Schottky diodes are used to isolate and protect the chassis power switch, improve the form of the connector, and reduce the power supply drop caused by the control circuit and the connector. At the same time, the power redundancy of the power supply is increased, which truly makes the backup power supply convenient and safe, and makes it more suitable for the requirements of long-term uninterrupted work.
10. Q: What function does the link alarm provided on the transceiver have?
Answer: The transceiver has a link alarm function (linkloss). When a fiber is disconnected, it will automatically feed back to the electrical port (that is, the indicator on the electrical port will also go out). If the switch has network management, it will be reflected to the switch immediately. Network management software.