Planar Lightwave Circuit Lattice Filter and Optical Transmitter Module Using Thereof

A planer lightwave circuit lattice filter for multiplexing a plurality of signal light beams of different wavelengths comprising:

• a plurality of input waveguides receiving input of the plurality of signal light beams;
• a multiplex circuit multiplexing the plurality of signal light beams;
• and
• at least one output waveguide outputting a multiplexed signal;
• wherein
• the multiplex circuit has an asymmetric MZI circuit cascaded in multiple stages;
• the asymmetric MZI circuit includes:
• an input-side coupler;
• an output-side coupler;
• and
• two waveguides which connect an output of the input-side coupler to an input of the output-side coupler and to which an optical path length difference is given, wherein
• two of the plurality of input waveguides are connected to inputs of the input-side coupler of each asymmetric MZI circuit arranged in a first stage;
• and
• the planer lightwave circuit lattice filter is configured so that a signal light beam in which the plurality of signal light beams output from the output-side coupler of the one asymmetric MZI circuit arranged in a final stage are multiplexed is coupled to the output waveguide.