In general, insertion loss represents the reduction in optical power as light travels through a certain path. It is measured by comparing the input power to the output power and often expressed in decibels, dB - see formula below.
Insertion loss is an important characterization for example in construction of fiber optic delay lines. Minimizing insertion loss is vital for preserving signal quality and intensity—particularly in applications like interferometry or coherent beam combining. Careful component selection (such as low-loss connectors), optimized optical alignment, and robust assembly techniques all help ensure that the optical path maintains as much signal power as possible.
