1. The module can emit light, but the measured optical power is much lower than the nominal value. The possible reasons are as follows:
a. The optical fiber is not inserted properly, re-plug the optical fiber and measure.
b. The fiber end face is damaged or contaminated, replace the fiber and re-measure it.
c. The end face of the optical module is damaged or contaminated. Use an end face tester to check the optical port of the module. If it is contaminated, clean and confirm that the end face is not damaged and re-measure.
d. The wrong type of fiber is used, for example, a multi-mode module uses a single-mode fiber to measure the optical power.
e. The wavelength of the optical power meter is inconsistent with the working wavelength of the module.
2. The possible reasons why the module does not emit light on the customer's switch are as follows:
a. The module is not compatible with the switch, causing the switch to prohibit the module from working.
b. The module has poor contact, and the golden finger is dirty, causing the module to not supply power normally.
c. TOSA is defective or damaged.
3. The possible reasons for the module cannot be identified or the DDM information is abnormal are as follows:
a. The module is not compatible with the switch, causing the switch not to read DDM content.
b. IIC communication is abnormal and the rate does not match.
c. The IIC pull-up resistor is missing, causing the data to be incorrectly transmitted.
d. The IIC program is wrong and cannot respond to the communication of the customer's exchange. Such as double/quad/multi-byte read and write.
e. The module MCU is damaged or the underlying file is abnormally cleared.
4. The possible reasons why the module cannot establish a connection on the switch are as follows:
a. The module is not compatible with the switch, causing the switch to prohibit the module workbench. If DDM can be displayed, check TX_PWR status to judge.
b. The received optical power is too small or there is no reception, the module reports RX_LOS, and communication is impossible. It can be judged by checking RX_PWR in DDM status. Some switches can display module alarms, faults and another working status.
c. Saturation of reception leads to excessive bit errors and communication failure. Easily appear on long-distance modules. When the customer detects the function of the module, the transceiver is directly connected to both ends of the module through the optical fiber jumper, which causes the received optical power to be too large. The module may be damaged.
d. The module is damaged and cannot work normally. Return to the factory for inspection.
5. The possible reasons for RX_LOS reporting too early, too late or not reporting RX_LOS are as follows:
a. DDM calibration error, the deviation is too large, the possibility is small, and the RX_LOS determination is generally completed by the chip comparing the output level of the TIA, rather than by the DDM optical power.
b. The customer's requirements do not match the scope of module debugging. In this case, you can only return to the factory to re-adjust the module.
c. The end face of ROSA is stained, causing the received light to be too small. Unlike TOSA, ROSA end faces cannot be inspected by an end face tester. They can only be returned to the factory or clean the end face on-site and try again.
d. The module is damaged and cannot work normally. Return to the factory for inspection.
6. TX_DIS function is abnormal, for example, TX cannot be turned off; or after TX_DIS is valid, DDM display is still normal or is not -40dBm. The possible reasons are as follows:
a. TX_DIS pull-up resistance is too large or missing, resulting in insufficient pin high-level voltage. Therefore, the TX_DIS signal cannot be recognized.
b. The chip is configured to forcibly turn on the TX function and does not respond to TX_DIS
c. After the MCU sampling accuracy causes the light to be turned off, there is still a small sampling AD, which is converted into the corresponding optical power by the software instead of -40dBm.
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