Performance analysis of optical amplifiers for Nyquist super channel transmission system

The thermal noise of photodiode detectors has a substantial impact on the performance of optical amplifiers in optical fiber communication systems. The presence of thermal noise at the photodiode detector reduces the Signal-to-Noise Ratio (SNR) of the receiver. In the case of optical amplifiers, this indicates that even if the amplifier increases the optical signal strength, the SNR may not improve as predicted if the detector’s thermal noise is substantial. The ability of an optical receiver to detect weak signals with little error is referred to as sensitivity. The higher levels of thermal noise in the photodiode result in less sensitivity since the detector is no longer capable of distinguishing weak signals from the background noise. Therefore, thermal noise might limit the detection of signals at very low power levels, even if there is optical amplification. This research centers on the optimization of a16 Nquist super channel DWDM systems utilizing hybrid designs of conventional optical fiber amplifiers (EDFA, RAMAN, SOA) and optical photodetectors (PIN, APD(Si), and APD(InGaAs)). The DWDM systems were developed for a channel speed of 20 Gb/s using one of these setups having a channel spacing of 20 GHz and a 25 km amplifier length. The hybrid configurations include (PIN + EDFA), (PIN + RAMAN), (PIN + SOA), (APD(Si) + EDFA), (APD(Si) + RAMAN), (APD(Si) + SOA), (APD (InGaAs) + EDFA), (APD (InGaAs) + RAMAN), and (APD (InGaAs) + SOA). The performance of these structures was analyzed based on BER, Q-factor, and eye diagrams under the conditions of different thermal noise levels of photodetectors over fiber lengths ranging from 25 to 150 km. The results indicated that both types of APD worked best at input powers of 5 dBm because of their strong internal avalanche gain. Both EDFAs perform better than either RAMAN or SOA amplifiers. SOA amplifier performance is limited by nonlinearity effects. This also makes it unsuitable for long-range DWDM systems as compared to RAMAN amplifiers that mitigate the effects of fiber non-linearity.