Patent ID: 8718412
Filing Date: 2014-05-06
Classification: G02F,H04B

Abstract:
1. A dual polarization quadrature phase shift keying (DP QPSK) optical modulator, comprising: an input port; an optical branching unit branching linearly-polarized light received from the input port into first through fourth linearly-polarized light components; an optical modulation unit connected to the optical branching unit, the optical modulation unit having first through fourth Mach-Zehnder interferometers that modulate the first through fourth linearly-polarized light components; a first phase-change unit connected to the third Mach-Zehnder interferometer, the first phase-change unit changing a phase of the third linearly-polarized light component; a second phase-change unit connected to the fourth Mach-Zehnder interferometer, the second phase-change unit changing a phase of the fourth linearly-polarized light component; an optical multiplexer coupling the second linearly-polarized light component and third linearly-polarized light component; and a multimode interference coupler including a multimode interference waveguide, first through third input ports extending in an optical waveguide direction, and an output port having a taper-shaped waveguide, the first through third input ports being provided along a direction orthogonal to the optical waveguide direction, the second input port being provided between the first input port and the third input port, wherein the first Mach-Zehnder interferometer is connected to the first input port of the multimode interference coupler, one end of the optical multiplexer is connected to the second Mach-Zehnder interferometer and the third Mach-Zehnder interferometer via the first phase change unit, the other end of the optical multiplexer is connected to the second input port of the multimode interference coupler, and the fourth Mach-Zehnder interferometer is connected to the third input port of the multimode interference coupler via the second phase-change unit.