| 摘要 |
PROBLEM TO BE SOLVED: To provide a wavelength filter in which long-distance transmission at a high speed is possible, expensive parts, such as an isolator in particular, are reduced, and cost reduction can be achieved, and an optical transmitter. SOLUTION: The wavelength filter is provided with 3 dB directional couplers 6, 12 having two input paths and two output paths, and these are cascade connected such that structure of a Mach-Zehnder interferometer type is obtained. The one input path 4 of the 3 dB directional coupler 6 and the one output path 16 of the 3 dB directional coupler 12 are connected via an optical resonator 17. Also, the other input path 8 of the 3 dB directional coupler 6 and the other output path 9 of the 3 dB directional coupler 12 are connected via an optical resonator 12. A terminal 5 of the one output path 7 of the 3 dB directional coupler 6 is an output section of the optical wave subjected to intensity modulation. The one input path 13 of the 3 dB directional coupler 12 is an output section of a reflected light component returning without passing the optical resonators 17, 18. Further, the other input path 11 of the 3 dB directional coupler 12 is an input section of the light wave from a laser beam source 10. COPYRIGHT: (C)2009,JPO&INPIT
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