Degradation of Bi-Directional Single Fiber Transmission in WDM-PON Due to Beat Noise

This paper presents a general formulation for the impact of back-reflection in wavelength division multiplexing-passive optical networks (WDM-PON) access networks. The analysis is applied to various wavelength-independent optical network unit (ONU) configurations such as amplified spontaneous emission (ASE)-locked Fabry-Perot (FP) lasers, reflective semiconductor optical amplifiers or injection locked FP using the downstream signal. The power penalty due to beat noise and its dependence on relative intensity noise, transmitter linewidth, and receiver bandwidth is investigated. The optimal gain at the ONU that minimizes the effect of beat noise is also found. The results show that the power penalty decreases as the linewidth of the the optical line terminal (OLT) and ONU light source increase.