To prevent the optical power at the receive end of an OTU board from being...

The fixed attenuator is usually configured at the receive end, not the transmit end, to prevent the optical power at the receive end of an OTU (Optical Transport Unit) board from being excessively high. High optical power at the receiver can cause signal distortion or damage the receiver module. Configuring the attenuator at the receive end ensures that the incoming signal power is within the optimal sensitivity range of the receiver. Configuring attenuators at the transmit end is generally ineffective because it reduces power output before transmission, potentially reducing reach. This approach aligns with HCIP-Transmission best practices for optical power management and receiver protection.