Design and Performance Analysis for a Binary-Driven QAM Transmitter

This paper presents the design analysis and performance simulation of binary-driven 16-QAM and 64-QAM optical transmitters that employ quadrature phase shift keying modulators in tandem. The design establishes the correct coupling ratios required for a proper constellation with equally spaced symbols. The analysis investigates the effect of coupling ratio errors as well as phase errors on bit-error-rate (BER) performance and constellation diagrams. The simulation results at 50 Gbaud with additive white Gaussian noise demonstrate high quality symbol constellation and BER performance that is identical to theoretical expectation. The 16-QAM transmitter achieved a BER better than 10 ^-4 and a power penalty of about 2 dB for coupling ratio errors less than 10% or phase errors within ±7°. For 64-QAM, BER better than 10 ^-4 and about 1 dB power penalty were obtained for coupling errors less than 3% or phase errors within ±2.7°.