Comparative Simulation of Thermal Noise Effects for Photodetectors on Performance of Long-Haul DWDM Optical Networks

Abstract

Abstract Long-haul 16-channel dense-wavelength division multiplexing networks employing two different avalanche photodiode (APD) structures (Si and InGaAs) and positive-intrinsic-negative (PIN) photodetectors are simulated and compared under thermal noise effects for different fiber lengths. The effect of thermal noise level on the transmission quality with a variation of amplifying section length, number of amplifying sections and channel speed is discussed. The impact of thermal noise on the system performance is analyzed by varying input power from −5dBm to 20dBm for both 25 km and 50 km amplifying section at 100 km fiber length. The performance is evaluated for both 5 Gb/s and 10 Gb/s data rates over transmission distances up to 500 km. A comprehensive comparison is developed based on signal-to-noise ratio (SNR), quality factor (Q-factor) and bit error rate (BER). It is found that both APD structures achieve superior performance up to distance of 350 km comparing to PIN photodetectors for 50 km amplifying section. The system provides optimum performance at input power P in = 10dBm in case of 50 km amplifying section, but then afterwards, the performance is degraded rapidly due to nonlinearities. The results revealed that the worst performance scenario is at 10–18 W/Hz thermal noise in terms of higher BER and lower Q-factor. Finally, the desirable BER of 10–12 is achieved at Q-factor of 6.78 and SNR of 23 dB.