An optical module can fail or produce errors if the input optical power exceeds its overload (saturated) optical power, which is the maximum average power the receiver can safely handle.

Understanding Overload Optical Power

The overload optical power (also called saturated optical power) is the upper limit of optical power that the receiver of an optical module can accept without malfunctioning or causing bit errors. If the input exceeds this limit, the photodetector may experience saturation, leading to temporary loss of sensitivity, misinterpretation of signals, and potential damage to the module . This value is typically specified in dBm on the module's datasheet.

Consequences of Exceeding the Limit

• Bit Errors: When the input optical power is too high, the receiver may misjudge the signal, increasing the bit error rate (BER) beyond acceptable levels (commonly BER = 10^-12), .
• Photodetector Saturation: Strong light can saturate the photodetector, requiring recovery time and temporarily reducing receiver sensitivity .
• Potential Damage: Prolonged exposure to optical power above the overload threshold can physically damage the photodetector or other internal components .

Practical Considerations

• Avoid Direct Strong Light: Never expose the module directly to high-intensity light sources, such as lasers not intended for the module, to prevent exceeding the overload power .
• Check Module Specifications: Each optical module has a defined receive power range, with the upper limit being the overload optical power and the lower limit being the receiver sensitivity .
• Rate and Sensitivity: Higher data rates generally reduce receiver sensitivity, meaning the module may tolerate less optical power before errors occur . In summary, the optical module will stop functioning correctly if the input optical power exceeds its overload optical power, causing bit errors, reduced sensitivity, or permanent damage. Always refer to the module's datasheet for the exact maximum input power and ensure the transmitted optical power stays within the safe operating range .