Patent ID: 8526102
Filing Date: 2013-09-03
Classification: H04B

Abstract:
1. A Planar Lightwave Circuit (PLC)-type demodulator that receives and demodulates a polarization-multiplexed coherent modulated signal, the demodulator comprising: one PLC chip in which a planar lightwave circuit is formed; a first input port provided at an input end of the PLC chip and inputting the polarization-multiplexed coherent modulated signal into the planar lightwave circuit; a second input port provided at the input end of the PLC chip and inputting local oscillation light into the planar lightwave circuit; at least one polarization beam splitter that splits the polarization-multiplexed coherent modulated signal input from the first input port into an X-polarization coherent modulated signal and a Y-polarization coherent modulated signal; a first 90-degree hybrid circuit that mixes and outputs the X-polarization coherent modulated signal and the local oscillation light input from the second input port; a second 90-degree hybrid circuit that mixes and outputs the Y-polarization coherent modulated signal and the local oscillation light input from the second input port; a second polarization beam splitter that splits the mixed light of the X-polarization local oscillation light and the Y-polarization local oscillation light into the X-polarization local oscillation light and the Y-polarization local oscillation light; a waveguide that connects the first input port and an input side coupler of the polarization beam splitter and has a bent region to fold propagating light; a waveguide that connects the second input port and the input side coupler of the second polarization beam splitter and has a bent region to fold propagating light; a first waveguide that connects an output side coupler of the polarization beam splitter and the first 90-degree hybrid circuit, transmits one of the X-polarization coherent modulated signal and the Y-polarization coherent modulated signal, and has a bent region to fold propagating light; a second waveguide that connects the output side coupler of the polarization beam splitter and the second 90-degree hybrid circuit, transmits the other of the X-polarization coherent modulated signal and the Y-polarization coherent modulated signal, and has a bent region to fold propagating light; a third waveguide that connects the output side coupler of the second polarization beam splitter and the first 90-degree hybrid circuit, transmits one of the X-polarization local oscillation light and the Y-polarization local oscillation light, and has a bent region to fold propagating light; and a fourth waveguide that connects the output side coupler of the second polarization beam splitter and the second 90-degree hybrid circuit, transmits the other of the X-polarization local oscillation light and the Y-polarization local oscillation light, and has a bent region to fold propagating light, wherein