The statement is correct. In Huawei Optical Amplifier (OA) systems, the lower threshold for the receive optical power is an alarm threshold, not the absolute operational limit. This threshold is intentionally set at a level higher than the receiver's sensitivity to provide a pre-warning and an operational safety margin. This margin allows network operators to detect and rectify degrading signal conditions before they lead to a significant increase in the Bit Error Rate (BER) and potential service disruption. For high-performance receivers, such as an Avalanche Photodiode (APD) on a line board or the WDM-side of an OTU board, a standard engineering margin of 5 dB is added to the receiver sensitivity value to set this lower alarm threshold.

A "False" answer would be incorrect because it would imply that the lower threshold is equal to the receiver sensitivity, or calculated differently. Setting the alarm threshold exactly at the sensitivity limit would provide no advance warning before service is impacted. The 5 dB margin is a crucial and documented design principle in Huawei's WDM/OTN systems to ensure network reliability and pro-active maintenance.

1. Huawei HCIP-Transmission V2.0 Training Material. In the module covering WDM System Design and Principles

the calculation for link power budgets and alarm thresholds is detailed. It specifies that the input optical power lower threshold (a pre-warning alarm) is configured above the receiver sensitivity to provide a system margin. The documentation states: "Lower threshold of the receive optical power = Receiver sensitivity + 5 dB." This ensures that an alarm is reported before the link performance degrades to the point of failure. (Refer to: HCIP-Transmission V2.0 Training Material

Module: WDM System Optical Power and Optical Signal-to-Noise Ratio).

2. Huawei OptiX OSN Product Documentation (e.g.

OptiX OSN 9800 Series). The Alarms and Performance Events Reference for Huawei's WDM/OTN platforms describes the trigger conditions for optical power-related alarms

such as INPUTPOWERLOW. The description for this performance event clarifies that its threshold is factory-set or configurable to be several dB above the board's specified receiver sensitivity to serve as an early warning indicator. The default value for this margin on line-side interfaces is typically 5 dB. (Refer to: Huawei OptiX OSN 9800 Product Documentation

Alarms and Performance Events Reference

Section: Optical Layer Performance Events).