A DWDM system for 256-QAM transmission over 4-km multimode fiber

摘要

A multichannel M-ary quadrature amplitude modulation (M-QAM) subcarrier multiplexed (SCM) lightwave transmission system can have transmission features such as high transmission capacity. Dense-wavelength-division-mulfiplexing (DWDM) systems can fully utilize the fiber bandwidth and increase the transmission capacity of a fiber link. A DWDM system that uses different optical channels to carry M-QAM digital signals would be quite useful for a fiber transport network providing high-speed data service due to the carrier-to-noise ratio (CNR) and carrier-to-nonlinear distortion ratio (CNLD) requirements of M-QAM signals are lower than those of AM-VSB signals. The theoretical C/(N+NLD) of 36 dB is required for the 256-QAM signals to achieve a BER ＜10{sup}(-9) when no error-correction coding is used [1,2], and each AM-VSB video channel with a 6-MHz bandwidth is expected to deliver a 256-QAM digital signal at a 40.1-Mbit/s data rate.