Avalanche photodiode (APD) receivers are commonly used on OTU boards due to their high sensitivity. The input optical power range typically lies between -4 dBm (maximum) and around -28 dBm (minimum).
Among the options, -4 dBm is within the acceptable input power range, ensuring the APD operates without saturation or damage. Optical powers too high can saturate the receiver, while too low powers cause poor signal-to-noise ratio. HCIP-Transmission specifies these ranges to ensure optimal receiver performance and avoid optical overload or underpower conditions.

The Delay Measurement (DM) function in MPLS-TP OAM can be used to measure the delay and jitter of service packets accurately. This function is essential for maintaining quality of service (QoS) in transport networks by monitoring timing and synchronization characteristics. Accurate delay and jitter measurement helps in diagnosing performance issues and ensuring service-level agreements are met. HCIP-Transmission emphasizes the use of DM in OAM for real-time monitoring and fault localization in MPLS-TP environments.