OPTICAL TRANSMISSION METHOD, OPTICAL TRANSMISSION SYSTEM, OPTICAL TRANSMITTER, AND OPTICAL RECEIVER

摘要

PROBLEM TO BE SOLVED: To improve anti-noise characteristic and improving receiver sensitivity in an optical transmission system.

SOLUTION: An optical transmitter 1 performs trellis encoding for transmission data with a trellis encoder 11, and applies, to the transmission data, an optical modulation in combining a QPSK (Quadrature Phase Shift Keying) modulation with a polarization modulation using a QPSK modulator 12 and a polarization modulator 13, and transmits the transmission data. An optical transmitter 2 performs polarization multiplexing at an optical hybrid circuit 21 and decodes the received data with a trellis decoder 25. The data is encoded with the trellis encoder and transmitted in the optical modulation with a multilevel modulation and the polarization modulation combined, so that the receiver sensitivity is improved by trellis code without increasing the multilevel number of the multilevel modulation.

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