The physics of noise in optical communication links is of great interest in the design of fiber optic communication systems. of the interfering chan-nel. We examine the importance of the FON term as well as the dependence of NLIN on modulation format with respect to li k-length and number of spans. The origins of noise in. FAN-YUAN Guan-Jie, XIE Wei-Xin, WANG Shuang, HAN Zheng-Fu. PHYSICS, 2025, 54 (8): 549-556. This noise, known as amplified spontaneous emission. However, besides unavoidable transmission loss, channel noise accelerates the decoherence of quantum states and severely limits the transmission distance in practical continuous-variable quantum state transmission.