FILTER ELEMENT

摘要

PURPOSE:To improve crosstalk characteristics with simple constitution by propagating a signal which is inputted to a filter element reciprocally in the element. CONSTITUTION:A Mach-Zehnder interferometer consists of optical demultiplexers 1-1 and 1-2 and optical waveguides 2 and 3 which couple those optical demultiplexers and an optical isolator 4 is coupled between a port C and a port D. At this time, the light signal which is inputted to a port A and outputted from a port B passes twice through the Mach-Zehnder interferometer which has exactly the same characteristics (from the port A to the port C and from the port D to the port B). Consequently, the two ports are only connected by using the element which propagates the signal only in one direction to improve the crosstalk characteristics.