Select the correct protection subtypes according to the descriptions.
When light passes through a passive optical component, the optical power decreases. This decrease is called an insertion loss.
In a coherent system, the incident optical power reference point in non-standard incident optical power is the output port of the OA board at the transmit end.
OTUk_DEG indicates OTUk signal degradation. Which of the following statements about the bit error detection mode are true? (Choose all that apply.)