We propose a polarization-multiplexing QPSK modulator for synthesis of a 16 QAM signal. The generation mechanism of 16 QAM is based on an electro-optic vector digital-to-analog converter, which can generate optical multilevel signals from binary electric data sequences. A quad-parallel Mach-Zehnder modulator (QPMZM) used in our previous research requires precise control of electric signals or fabrication of a variable optical attenuator, which significantly raises the degree of difficulty to control electric signals or device fabrication. To overcome this difficulty, we developed the polarization-multiplexing QPSK modulator, which improved the method of superposition of QPSK signals. In the polarizationmultiplexing QPSK modulator, two QPSK signals are output with orthogonal polarization and superposed through a polarizer. The amplitude ratio between the two QPSK signals can be precisely controlled by rotating the polarizer to arrange the 16 symbols equally. Generation of 16 QAM with 40 Gb/s and a bit error rate of 5.69 × 10 -5 was successfully demonstrated using the polarization-multiplexing QPSK modulator. This modulator has simpler configuration than the previous one, utilized a dual-polarization MZM, alleviating complicated control of electric signals.
- Modulation format electro-optic vector digital-to-analog converter
- Polarization multiplexing
- Quad-parallel Mach-Zehnder modulator
- Quadrature amplitude modulation
ASJC Scopus subject areas
- Computer Networks and Communications
- Electrical and Electronic Engineering