1. No lights when plugging into the switches

a. Modules can't be compatible with the switches, caused the switch forbid the modules to work, such as compatible Cisco modules used in the Juniper switch;

b. Modules is defective, the gold finger is scratched, caused the modules can't supply the power normally;

c. TOSA is bad or damaged.

2. Modules Can't be identified or DDM info. is abnormal:

a. Modules can't be compatible with the switches, caused the DDM info. can't be read;

b. I2C communication is abnormal, the rate isn't matched with the switches;

C. I2C pull-up resistor is missed, caused the data can't be transmitted correctly;

d. I2C program has problems, can't match the customers' switches.

3. No Link with switches:

a. Modules can't be compatible with the switches, caused the switch forbid the modules to working.

b. Receiver optical power is too small or can't be received, modules display RX_LOS can't communicate ----- can be read via RX_PWR of DDM.

Some switches can display the alarm/ malfunction ... working condition.

c. Receiver overload, caused bit error is too large to communicate ----- usually happens on the long distance modules, direct connecting  the modules with the patch cords, caused the receiver rate is too large, and will damage the modules.

d. Modules is damaged ---- return back to the supplier to test.

4. Modules Can light, but the optical power is much lower than the standard data:

a. Optical fiber isn't matched very well ----re-plug the modules and test again;

b. Optical fiber transverse is damaged or dirty ---- replace the optical fiber and test again;

c. Using the wrong optical fiber, such as SM modules used MMF;

d. Modules wavelength is different from the optical power meter.