Optical Transceiver Troubleshooting

The role of fiber optic transceivers

Since the maximum transmission distance of the network cable (twisted pair) we often use is very limited, the maximum transmission distance of the twisted pair is generally 100 meters. Therefore, when we are deploying a larger network, we have to use relay devices. Optical fiber is a good choice. The transmission distance of optical fiber is very long. Generally speaking, the transmission distance of single-mode optical fiber is more than 10 kilometers, and the transmission distance of multi-mode optical fiber can reach up to 2 kilometers. When using optical fibers, we often use optical fiber transceivers:

If you want to know how to use a fiber optic transceiver, you must first know what the fiber optic transceiver does. To put it simply, the function of the fiber optic transceiver is to convert between optical signals and electrical signals. The optical signal is input from the optical port, and the electrical signal is output from the electrical port (common RJ45 crystal head interface), and vice versa. The process is roughly as follows: convert the electrical signal into an optical signal, transmit it through an optical fiber, convert the optical signal into an electrical signal at the other end, and then connect it to routers, switches and other equipment.

Therefore, fiber optic transceivers are generally used in pairs. If you want to use fiber optic transceivers to build your own LAN, you must use them in pairs. The general optical fiber transceiver is the same as the general switch, it can be used after being powered on, and no configuration is required.

How to use fiber optic transceiver

The general optical fiber transceiver is the same as the general switch, it can be used after being powered on, and no configuration is required. Optical fiber port, RJ45 crystal plug power port. But pay attention to the sending and receiving of optical fibers, one for receiving and one for sending, and if it doesn't work, replace each other.

Fault Judgment Method of Fiber Optic Transceiver

There are many types of optical fiber transceivers, but the fault judgment methods are basically the same. In summary, the faults that occur in optical transceivers are as follows:

1. The Power light is off:

electricity failure

2. The link light of the optical path is not on. The fault may be as follows:

A. Check whether the optical fiber line is broken.

B. Check whether the loss of the optical fiber line is too large, exceeding the receiving range of the equipment.

C. Check whether the optical 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 fiber optic connector is inserted into the device interface in good condition, 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. If the link light of the circuit is not on, the fault may be as follows:

A. Check whether the network cable is broken

B. Check whether the connection type matches: use crossover cables for network cards and routers, and use straight-through cables for switches, hubs and other devices.

C. Check whether the transmission rate of the device matches.

4. Severe network packet loss. Possible faults 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 does not match.

B. If there is a problem with the twisted pair and the RJ-45 head, check it.

C. Fiber connection problem, whether the jumper is aligned with the device interface, whether the pigtail and jumper and coupler type are matched, etc.

5. After the fiber optic transceiver is connected, the two ends cannot communicate

A. The optical fiber is reversed, and the optical fiber connected to TX and TR is reversed.

B. The connection between the RJ45 interface and the external equipment is not correct (pay attention to straight-through and splicing)

The optical fiber interface (ceramic ferrule) does not match. This fault is mainly reflected in the 100M transceiver with photoelectric mutual control function. If the pigtail of the APC ferrule is connected to the transceiver of the PC The optoelectronic mutual control transceiver has no effect.

6. On and off phenomenon

A. It may be that the optical path attenuation is too large. At this time, an optical power meter can be used to measure the optical power at the receiving end. If it is around the range of receiving agility, it can be basically judged as an optical path failure within the range of 1-2dB.

B. It may be that the switch connected to the transceiver is faulty. At this time, replace the switch with a PC, that is, the two transceivers are directly connected to the PC, and both ends are PING. If there is no intermittent connection, it can be basically judged as a switch failure.

C. It may be the fault of the transceiver. At this time, you can connect the two ends of the transceiver to the PC (not through the switch). After the two ends have no problem with PING, transfer a large file (100M) or more from one end to the other end, and observe its status. Speed, if the speed is very slow (file transfer below 200M takes more than 15 minutes), it can be basically judged as a failure of the transceiver.

7. After a period of communication, it crashes, that is, it cannot communicate, 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 discard the packets with errors, and forward the correct packets. However, in this process, some packets with errors cannot be detected in the CRC error detection and length inspection. Such packets will not be sent out during the forwarding process, nor will they be discarded. They will be accumulated in the dynamic cache ( buffer), it can never be sent out, and when the buffer is full, it will cause the switch to crash. Because at this time, restarting the transceiver or restarting the switch can restore the communication to normal, so users usually think that it is a problem with the transceiver.

8. Transceiver test method

If you find that there is a problem with the transceiver connection, please test as follows to find out the cause of the failure

A. Proximity test

Ping the computers at both ends. If the PING can pass, it can be confirmed that there is no problem with the fiber optic transceiver. If the near-end test fails to communicate, it can be judged that the fiber optic transceiver is faulty.

B. Remote test

The computers at both ends are PING. If the PING fails, you must check whether the optical path connection is normal and whether the transmitting and receiving power of the optical fiber transceiver is within the allowed range. If the PING is normal, it proves that the optical path connection is normal. It can be judged that the fault problem is on the switch.

C. Remote test to determine the fault point

First connect one end to the switch, and then PING both ends. If there is no fault, it can be judged that the other switch is faulty.