1. The optical fibers are reversed, and the optical fibers connected to TX and RX are reversed.

2. The connection between the RJ45 interface and the external device is incorrect (pay attention to the straight-through and splicing) and the optical fiber interface (ceramic ferrule) does not match. This fault is mainly reflected in the 100M transceiver with optoelectronic mutual control function, such as the pigtail of the APC ferrule The transceiver connected to the PC ferrule will not be able to communicate normally, but it will not affect the connection of the non-optical mutual control transceiver.

6. The phenomenon of on-off and on-off:

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

2. It may be the fault of the switch connected to the transceiver.

At this time, replace the switch with a PC, that is, the two transceivers are directly connected to the PC, and the two ends are pinged.

3. It may be the failure 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, and observe it. If the speed is very slow (files under 200M are transmitted for more than 15 minutes), it can be basically judged that the transceiver is faulty.