OPTICAL SIGNAL QUALITY MONITORING APPARATUS, OPTICAL TRANSMISSION APPARATUS, AND OPTICAL SIGNAL QUALITY MONITORING METHOD

摘要

PROBLEM TO BE SOLVED: To provide an optical signal quality monitor capable of achieving simplicity and cost reduction without giving penalty to main signal light.SOLUTION: The present invention comprises: an optical filter 11 that enables an optical signal formed by superposing modulation signals of frequency or phase to penetrate through a part of spectrum thereof, and a detection section 17 that detects signal quality of the optical signal on the basis of a power ratio of a signal component to a noise component of the modulation signal, obtained based on a power change suited to the modulation signal of the light which has penetrated through the optical filter 11.