ARRANGEMENT STRUCTURE OF MULTIPATH OPTICAL FILTER SYSTEM AND ITS OPTICAL FILTER WITH LENS

摘要

PROBLEM TO BE SOLVED: To obtain a multipath optical filter system, which has small coupling loss of a light beam and also has superior filtering characteristic. SOLUTION: Two filters 70a and 70b with lenses, which are constituted by arranging filter elements 8 between back surfaces of two GRIN lenses 10a and 10b, are arranged one after the other. The optical axis of the filter 70b is offset parallel to the optical axis of the filter 70a by twice as much as the offset of an incident light beam to an input port 12 to the optical axis of the filter 70a. A beam which appears at an output port 16 from the input port 12 through the filter 70a travels through the same path of the filter 70b with the return path from the output port 16 to the input port 12 and exits from the output port of the filter 70b. Beams traveling through the filters 70a and 70b are made to pass through a filter element 8 at the intersecting position of the optical axes 73a and 73b of the filters.