| 摘要 |
PROBLEM TO BE SOLVED: To prevent the transmission light emitted from a light emitting element from being undesirably made incident on the light receiving surface of a light receiving element through a demultiplexing filter after this light is reflected by the demultiplexing filter. SOLUTION: This module makes the transmission light of a wavelengthλ1 emitted from an LD (light emitting element) 6 incident on an optical fiber 12 through the demultiplexing filter 5, reflects the reception light from the end face of the optical fiber 12 by the demultiplexing filter 5 and makes this light incident on a PD (light receiving element) 9. In such a case, a cover 40 covering the front of the demultiplexing filter 5 is deposited at a casing block 20 and a tongue piece 41 as a return light preventing means is formed at the cover 40. When the transmission light from the LD 6 is reflected by the demultiplexing filter 5, the reflected light thereof is directionally changed by this tongue piece 41 so as not to be made incident on the PD 9.
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