| 摘要 |
PURPOSE:To set up accurately a coupling ratio with a low insertion loss by forming optical phase shifters at least on one of two optical waveguides coupling between two directional couplers so that the optical length is finely adjusted. CONSTITUTION:The two optical waveguides are constituted of quartz glass optical waveguides. Two photocoupling pars 21, 22 have quite the same constitution and form two directional couplers respectively to constitute a kind of optical interferometer. In the waveguide type optical interferometer having said constitution, it is unnecessary to set up the directional couplers 21a, 21b, 22a, 22b constituting the photocoupling parts 21, 22 accurately to 50% coupling ratio. Because the coupling ratio of the whole photocoupling parts 21, 22 can be tuned to 50% by driving the phase shifters 21c, 21d and 22c, 22d to execute fine adjustment of the optical length difference between the coupling optical paths. thereby, it is good enough to set up the coupling lengths of individual couplers 21a, 21b, 22a, 22b to 1/4 the complete coupling length or more, so that the allowable accuracy of production can be extremely loosened. |
