| 摘要 |
PURPOSE:To multiplex optical signals with minimum loss when an element is used as an optical multiplexing element and to demultiplex optical signals with minimum crosstalk when the element is used as an optical demultiplexing element by providing either of an input branch part and an output branch part with a branching ratio adjusting part which varies the branching ratio of the branching part. CONSTITUTION:Two input light guides 2 and output light guides 3 each are formed nearby on the surface of a substrate 1. Then the directional coupler type input branch part and output branch part 5 with an about 1:1 branching ratio are constituted and an electrode 7 is formed as the branching ratio adjusting part on the surfaces of the output light guides 3. A voltage is impressed to the electrode 7 to vary the propagation constant difference of an output photocoupler 5, whose branching ratio is varied to maximize the intensity of a optical signal at an output terminal 10. The different point between the constitution of the optical demultiplexing element and the constitution of the optical multiplexing and demultiplexing element is that the electrode 13 as the branching ratio adjusting part is formed not at the output photocoupler 5, but at the input photocoupler 5. Consequently, when the element is used as the optical multiplexing element, optical signals are multiplexed with minimum loss and when used as the optical demultiplexing element, the light signals are demultiplexed with minimum crosstalk. |
