| 摘要 |
PROBLEM TO BE SOLVED: To provide a method for designing an optical filter of narrow relative band which does not cause linear distortion to both a selective characteristic which excludes interfering signal and passing wanted signal, to realize the filter. SOLUTION: Related to a 2-port optical filter module, a multiplex thin-film optical filter and a phase shifter are connected in parallel between an input port and an output port with a coupler in between. The electrical length of the phase shifter including the coupler is different from that of the transmission line before and after the multiplex optical thin-film filter including the coupler by odd-number multiple ofλ0 /4, whereλ0 is central wavelength of passing signal.
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