Optimizing Probabilistic Constellation Shaping for Amplifier-Less Coherent Optical Links

Coherent optical systems for short-reach links have seen a boost in their popularity with the standardization of 400ZR. These need to be cost and power-efficient, while coping ever increase traffic demand. The use probabilistic constellation shaping (PCS) can help meet these demands, since it reduces gap channel capacity. However, studies concerning PCS typically include amplification; therefore, its gain amplifier-less has been somewhat uncertain. In this work, we focus on an coherent link employing PCS, reducing both power consumption system complexity due removal amplifier. We employ different modulation orders bit rates, optimizing several key parameters such as FEC coding overhead, depth clipping. With comprehensive study, demonstrate by simulation experimental validation that is beneficial even systems, introduces residual gains allowing higher flexibility defining net rate fixed baud rate.