Method to generate 112 Gbit/s polarisation-multiplexed 8QAM signal

Proposed is a new method to synthesise the 8-ary quadrature amplitude modulation (8QAM) signal and demonstrate the 112 Gbit/s polarisation-multiplexed 8QAM system. The proposed transmitter consists of a dual-drive Mach-Zehnder modulator (DD-MZM) and phase modulators in tandem. The DD-MZM is utilised to manipulate the amplitude and phase of the optical signal by adjusting its chirp. The optical signal-to-noise ratio sensitivity of the 112 Gbit/s polarisation-multiplexed 8QAM signal to achieve the bit error rate of 10−3 is measured to be 18.8 dB (in 0.1 nm resolution bandwidth).