Equalization & carrier recovery for 112Gbps optical coherent system with HEX-16-QAM modulation

We propose and demonstrate a new 112 Gbps Polarization division Multiplexing digital optical coherent systems with hexagonal 16-QAM (HEX-16-QAM) modulation. In our proposed system we use decision directed dispersion compensation algorithm which is Least Mean Square (LMS) algorithm and single tap decision directed carrier recovery algorithm. We compare the HEX-16-QAM systems with 16-QAM system for uncompensated transmission. Our analysis result found that HEX-16-QAM can achieve bit error rate (BER) of 1.5×10-4 whereas square 16-QAM BER is 5×10-4 for uncompensated 500-km transmission at 25 dB OSNR. Propose system achieve 0.3 dB OSNR penalty with compare to square 16-QAM system. © 2012 IEEE