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Synthesis of 16 Quadrature Amplitude Modulation Using Polarization-Multiplexing QPSK Modulator
Isao MOROHASHI Takahide SAKAMOTO Masaaki SUDO Atsushi KANNO Akito CHIBA Junichiro ICHIKAWA Tetsuya KAWANISHI
IEICE TRANSACTIONS on Communications
Publication Date: 2011/07/01
Online ISSN: 1745-1345
Print ISSN: 0916-8516
Type of Manuscript: Special Section PAPER (Joint Special Section on Opto-electronics and Communications for Future Optical Network)
modulation format electro-optic vector digital-to-analog converter, quadrature amplitude modulation, quad-parallel Mach-Zehnder modulator, polarization multiplexing,
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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 polarization-multiplexing 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 5.6910-5 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.