Simplified coherent optical transmissions utilizing noise shaping and non-integer-oversampling clock data recovery

Abstract

To meet the ever-increasing demand for data traffic, the simplified coherent optical communications, which exhibit the advantages of low cost, low power consumption and high capacity, have garnered the widespread attention for short-reach optical communications applications. To further reduce the cost of coherent optical transmissions, we for the first time propose and demonstrate the capability of non-integer-oversampling clock data recovery (CDR) to process the noise-shaped signals which is robust to the quantization noise when using cheap digital-to-analog converters (DACs). The 192-Gbps dual-polarization quadrature amplitude modulation-16 (DP-QAM-16) transmissions are experimentally realized by jointly implementing the noise shaping (NS) technique and 4/3 samples per symbol (sps) CDR processing. Experimental results indicate that 1.2-and 1-dB Q factor gains have been achieved by using the proposed simplified coherent optical transmission structure, under the constraints of 3-and 4-bit quantization respectively. We believe that the joint implementation of NS and non-integer-oversampling CDR is promising for simplifying the coherent optical transmissions for low-cost optical communications applications.