OPTICAL AMPLIFICATION SYSTEM

摘要

PURPOSE:To suppress deterioration of a relative intensity noise due to reflected light even when an optical fiber which has a specific refractive index difference different from an ordinary one is connected by providing an optical isolator which has a specific quenching ratio on both or one of the incidence side and projection side of an optical fiber type optical amplifier. CONSTITUTION:A photodiode 8 for monitoring signal light alpha1 which is made incident on the optical amplification system is connected between incidence-side optical fibers 9' and 9 through a coupler 10 for monitoring. Further, a photodiode 11 for monitoring amplified light alpha1' projected from the optical amplification system is connected between projection-side optical fibers 12 and 12' through a coupler 13 for monitoring, and a dispersion compensation optical fiber 14 is connected by fusion splicing to the tip of the projection-side optical fiber 12' at a part C1. An incidence-side optical isolator 7 which has a 50dB quenching ratio is used and a projection-side optical isolator 6 which has a 60dB (>=50dB) extinction ratio is used.