Next-generation optical metro+access network using coherent detection

In today’s digitalized world, the demand for data transmission continues to grow, pushing network capacities to their limits. While coherent transceivers effectively meet user demands in long-haul transmissions, new solutions are required for metro access networks. This challenge arises due to the different detection technologies used in metroaccess passive optical networks (PONs), specifically Intensity Modulation Direct- Detection (IMDD). From a capacity perspective, IMDD is significantly limited compared to coherent detection, as it does not support advanced modulation formats that provide higher spectral efficiency. On the other hand, implementing coherent transmission is more complex and costly, making it unsuitable for the PON context. The proposed solution is a simplified version of the coherent detection technology used in long-haul transmissions, optimized for metro access PONs (referred to as Lite Coherent). This project primarily focuses on implementing a digital signal processing (DSP) coherent receiver capable of handling typical PON impairments, such as phase noise, frequency offset, and others. To enhance robustness in the developed optical system, the project explores an alternative modulation scheme: Differential Quadrature Phase Shift Keying (DQPSK), as opposed to the conventional Quadrature Phase Shift Keying (QPSK). Through comprehensive performance analysis, the results demonstrate that DQPSK is a viable modulation option for access network scenarios.