BRANCH LINE MONITORING SYSTEM/METHOD

摘要

PROBLEM TO BE SOLVED: To provide an inexpensive branch line monitoring system and its method to improve the SN ratio of measured information. SOLUTION: Optical filters 41-44 are installed in accordance with optical fiber lines 11-14 to be monitored as branch lines. The optical filters 41-44 have cutoff characteristics to cut off one wave out of monitoring light beams λ1 -λ4 while allowing the remaining monitoring light beams and signal light to pass through. By installing the optical filters 41-44 having such cutoff characteristics, the optical fiber lines 11-14 are monitored by using a plurality of monitoring light beams except for the light beam interrupted by the optical filters 41-44. Thus, the SN ratio of measured information is much more improved and more precise monitoring is realized compared with a case when one optical fiber line is monitored by the corresponding one monitoring light wave.