It is false that output optical power of a site must be as high as possible to ensure signals reach the peer site. Excessively high output power can cause nonlinear effects, such as four-wave mixing and self-phase modulation, degrading signal quality. Optimal power levels must be maintained within equipment specifications to balance reach and signal integrity. HCIP-Transmission stresses careful power management, including gain control and attenuation, to maximize network performance without introducing impairments.

ESC (Enhanced Supervision Channel) uses Fixed frame structure DCC and Embedded DCC types to transmit supervisory and management information within the optical channel.

A parallel FOADM site typically uses an EX40+EMR8 networking mode, where EX40 handles add/drop functions and EMR8 manages multiplexing and amplification.

The term “Directioned” in WDM systems means that the wavelength carrying local services can be transmitted in a specific direction. This contrasts with directionless systems, where wavelengths can propagate in either direction without restriction. Directioned capability allows more controlled and secure wavelength routing, especially in ring or mesh networks where traffic flows need clear paths. Colorless refers to wavelength independence (a device can handle any wavelength), while colored means the device or port is assigned to a fixed wavelength. Thus, directioned accurately describes the wavelength propagation direction property as per HCIP-Transmission explanations on optical network design and wavelength routing.

SOTU denotes a single-OTU interface that supports one OTU channel, whereas MOTU denotes a multi-OTU interface capable of handling multiple OTU channels.

When light passes through a passive optical component, the decrease in optical power is termed insertion loss. This is a fundamental concept in optical transmission where every component like connectors, splices, splitters, or filters adds some level of power attenuation. Managing insertion loss is crucial to maintain overall system performance, especially in long-haul or dense WDM systems where accumulated loss can degrade the signal. HCIP-Transmission emphasizes the importance of measuring and minimizing insertion loss to ensure system stability and reach requirements are met.

With an initial RI1–RI2 difference of 2 dB and a 5 dB threshold, only when the active channel’s loss increases by 7 dB (to 3 dBm) while the standby remains at 8 dBm does the difference reach 5 dB and trigger switching.