Why is it common practice to set the average amplitude of digital modulation channels 6 to 10 dB below the maximum specified into the laser?

The practice of setting the average amplitude of digital modulation channels 6 to 10 dB below the maximum specified into the laser is primarily intended to reduce noise that may accompany the channel. Operating at this lower average amplitude helps to mitigate the effects of signal distortion and system noise, ensuring that the signal remains clear and reliable during transmission.

By maintaining a threshold below the maximum, digital systems can handle variations in signal quality and external interference more effectively. This reduction in amplitude can enhance the signal-to-noise ratio, which is crucial for improving the overall performance of the communication system. A cleaner signal ensures better data integrity and reduces the likelihood of errors during transmission, allowing for more efficient communication and data transfer.

While there may be factors such as compliance with regulatory standards or prevention of signal loss that are also important in the broader context of digital communication systems, the primary rationale for this specific amplitude setting revolves around the reduction of noise and the maintenance of signal clarity.