BAND ELIMINATION OPTICAL FILTER AND OPTICAL MULTIPLEXER/ DEMULTIPLEXER

摘要

PROBLEM TO BE SOLVED: To eliminate an optical signal with a prescribed wavelength region by reflecting a light at a prescribed wavelength region to an isolator with a selective reflecting means and transmitting other lights without reflection. SOLUTION: The filter is provided with a selective reflection fiber 10 that reflects selectively a specific wavelength by forming a part whose refractive index is changed periodically, that is, a fiber grating in the lengthwise direction of its core and an optical isolator 12 that propagates an optical signal with a low loss in one direction and has a low for the propagation in the opposite direction, and the selective reflection fiber 10 is molten and connected to an output of the optical isolator 12. Then the optical signal 20 received by the optical isolator 12 receives no effect by the optical isolator 12 but is given to the selective reflection fiber 10 as it is. In this case, the selective reflection fiber 10 reflects only the optical signal with a wavelength of λ3. Then the optical signal 24 with the wavelength λ3 reflected by the selective reflection fiber 10 is made incident to the optical isolator 12 in an opposite direction and attenuated largely.