Patent ID: 9197328
Filing Date: 2015-11-24
Classification: H04B

Abstract:
1. An optical transmitter, comprising: a first quadrature phase shift keying (QPSK) modulator including a first Mach-Zehnder (MZ) interferometer and a first waveguide, the first QPSK modulator outputting a first optical signal, the first waveguide showing a Quantum Confined Stark Effect (QCSE), being coupled with an output port of the first MZ interferometer, and having a first electrode configured to receive a first bias, an optical power of the first optical signal decreasing as the first bias increases; and a second QPSK modulator including a second MZ interferometer and a second waveguide the second QPSK modulator outputting a second optical signal, the second waveguide showing the QCSE, being coupled with an output port of the second MZ interferometer, and having a second electrode configured to receive a second bias, an output power of the second optical signal decreasing as the second bias increases, wherein the optical transmitter outputs only the first optical signal when the first bias is set to substantially zero volts and the second bias is set to a voltage higher than a first critical voltage, and outputs only the second optical signal when the first bias is set to another voltage higher than a second critical voltage and the second bias is set to substantially zero volts.