The main performance indicators of optical connectors are: insertion loss and return loss.
1. Insertion loss
Insertion loss refers to the decibel of the ratio of the output optical power to the input optical power after the optical signal in the optical fiber passes through the optical connector.
The expression formula is: IL=-10lg (output optical power/input optical power), unit: decibel (dB).
During use, the smaller the insertion loss, the better.
The main factors affecting insertion loss are: fiber surface cleanliness, axis inclination, lateral offset, and fiber gap.

2. Return loss
Return loss, also known as retroreflection loss, refers to the decibel ratio of the ratio of the retroreflected optical power to the input optical power at the fiber connection.
The expression formula is: RL=-10lg (back-reflected optical power/input optical power), unit: decibel (dB).
During use, the larger the return loss, the better, to reduce the impact of reflected light on the light source system.
The main factors that affect the return loss are: fiber surface cleanliness, end face polishing quality, fiber unevenness, and end face grinding methods (PC and APC).