The average transmission power: The average transmission power of the fiber optic module refers to the optical power output by the emission end light source under normal working conditions, which can be understood as the intensity of light. The transmission power is related to the proportion of "1" in the data signal sent. The more "1" there are, the greater the optical power will be. When the transmitter sends a pseudo-random sequence signal, "1" and "0" roughly occupy half of the total, and the power obtained at this time is the average transmission power, which is measured in W or mW or dBm. Among them, W or mW are linear units and dBm are logarithmic units. In communication, we usually use dBm to represent optical power.
Extinction ratio: The extinction ratio is the minimum ratio of the average optical power of the laser emitted under full modulation conditions when transmitting all "1" code to the average optical power of the laser emitted when transmitting all "0" code, and it is measured in dB. As shown in Figure 1-3, when we convert the electrical signal into an optical signal, the fiber optic module emitting part of the laser converts it into an optical signal according to the input electrical signal rate. The average optical power when transmitting all "1" code represents the average power of the laser emitting, and the average optical power when transmitting all "0" code represents the average power of the laser not emitting, and the extinction ratio reflects the ability to distinguish between 0 and 1 signals. Therefore, the extinction ratio can be viewed as a measure of the operating efficiency of the laser. The typical minimum range of the extinction ratio is 8.2 dB to 10 dB.
Overload optical power, also known as saturation optical power, refers to the maximum effective average optical power (in dBm) the receiving end component of the fiber optic module can receive under a certain bit error rate (BER = 10^-12). It should be noted that the photodetector will exhibit photoelectric current saturation under strong light irradiation. When this phenomenon occurs, the detector needs a certain amount of time to recover. At this time, the receiving sensitivity decreases, and the received signal may have an error judgment and cause an error code. Simply put, if the input optical power exceeds this overload optical power, it may cause damage to the device. It should be avoided to avoid exceeding the overload optical power during operation.
Receiving sensitivity: The receiving sensitivity refers to the minimum average input optical power that the receiving end component of the fiber optic module can receive under a certain bit error rate (BER = 10^-12). If the transmitted optical power refers to the intensity of the light emitted by the transmitting end, then the receiving sensitivity refers to the strength of the light the fiber optic module can detect (measured in dBm). Generally speaking, the higher the rate, the worse the receiving sensitivity, that is, the larger the minimum received optical power, and the higher the requirements for the receiving end device of the fiber optic module.