Optical DQPSK video system with heterodyne detection
- 1 March 1991
- journal article
- Published by Institute of Electrical and Electronics Engineers (IEEE) in IEEE Photonics Technology Letters
- Vol. 3 (3) , 262-264
- https://doi.org/10.1109/68.79774
Abstract
An optical heterodyne subcarrier-multiplexed (SCM) quadrature-phase-shift keying (QPSK) system is described that employs differential encoding to transmit multiple video channels. With this differential encoding scheme, only a simple delay-and-multiply demodulator is necessary, considerably reducing the signal processing complexity. The demodulators reproduce the data in a parallel fashion so no baseband demultiplexing or four-level decision circuit is required. This approach also avoids the complications of implementing a carrier recovery circuit (CRC) and a phase-locked loop associated with coherent microwave demodulation schemes. In addition to bandwidth efficiency and simplicity, differential QPSK also provides very good receiver sensitivity. With heterodyne detection, a receiver sensitivity of -41 dBm is achieved.Keywords
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