This major source of interconnection losses occurs when modes are lost as signals travel from one fiber into another fiber that supports fewer nodes. Reduction of core radius Aperture losses, another major source of interconnection losses, occur due to the signal leakage that takes place when signals travel from a fiber with a larger core to a fiber with a smaller core. Misalignment Losses Lateral Longitudinal Angular Reflection Losses Reflection losses occur when signals cross the interface between two propagation media with different refractive indices. This can add noise or shift the operating wavelength. Duplex operations are especially vulnerable due to crosstalk between the transmitter and receiver.
Large reflections can damage higher power lasers.
A demultiplexer's output center wavelength must coincide with the channel center wavelength. The narrower the channel spacing, the more precise the demultiplexer's center wavelength must be. The PWVL should be measured with unpolarized light due to polarization dependencies. The NWVL is the wavelength for which the demultiplexer is designed. The PWVL of the demultiplexer output is the wavelength with the smallest insertion loss.