## 4 Simulation Results and Discussion
### Impact of Input Noise
The output ER and CR performances under different input OSNRs are plotted in Figure 10. As shown in Figure 10a, the output ER decreases as the input OSNR decreases for both input frequencies. However, the input frequency of 192.8 THz can achieve a larger output ER value by about 4.86% on average compared with the input frequency of 193.4 THz, where the maximum ER improvement can reach 2.04 dB when the input OSNR is around 18 dB. Some studies indicate that the output exhibits comparatively superior quality when the typical empirical value of ER is above 9 dB [28]. Note that even at an input OSNR of 10 dB, where the quality of the input signal deteriorates seriously, the output ER values remain superior to the empirical benchmarks of 0.81 dB and 0.04 dB for 192.8 THz and 193.4 THz, respectively. In Figure 10b, it can be observed that as the input OSNR decreases, the output CR also decreases for both input frequencies. These two curves are very close, where the input frequency of 192.8 THz can achieve a slightly larger output CR value by about 0.33% on average compared with the input frequency of 193.4 THz, which means they have very similar CR performance. This is because these two frequencies are symmetrical about the center frequency of the local CW, and the gains of the amplifier following the right switch are 20.06 dB and 20.02 dB for the two input frequencies, which are almost the same. Then, the impact of input noise on the bit-recognition result should be almost the same. Therefore, when the input frequencies are 192.8 THz and 193.4 THz and the transmission rate is 100 Gbps, the output ER and CR results of the proposed system exhibit similar performance. Figure 11 shows the Q factor and BER performances under different input OSNRs. In Figure 11, the Q factor results exhibit a similar trend to those of ER and CR, where the value of the Q factor decreases as the input OSNR decreases for both input frequencies. When the input OSNR is larger than 20 dB or less than 8 dB, the input frequency of 193.4 THz can achieve a larger Q factor value compared with the input frequency of 192.8 THz. On the other side, the input frequency of 192.8 THz shows better performance when the input OSNR is between 8 dB and 20 dB. Generally, the input frequency of 193.4 THz can achieve a slightly larger Q factor value by about 0.14% on average compared with the input frequency of 192.8 THz. The BER performance under different qualities of input signal is shown in Figure 11. Once the BER exceeds \(10^{-2.4}\), the signal becomes uncorrectable due to the forward error correction threshold limitation. Then, the BER performance is analyzed based on the green reference line in the figure. The results indicate that the OSNR at the input frequency of 193.4 THz is approximately 0.50 dB higher than that at 192.8 THz when the BER is \(10^{-2.4}\). Figure 12 presents the AM and SNR performances at two frequencies of 192.8 THz and 193.4 THz under different input OSNRs. From Figure 12, it is evident that the output AM progressively rises as the input OSNR decreases. This indicates that the higher the quality of the input signal, the smaller the amplitude fluctuation of logic \"1\" and the more stable the signal. In the high OSNR regime (OSNR > 18 dB), the value of AM is very small, and as input OSNR increases, the rate of decrease in AM gradually  
\[ER(dB)=10\log\left(\frac{P_{\min}^{1}}{P_{\max}^{0}}\right) \tag{11}\]0 Output performances of (a) Q factor; and (b) BER under different input OSNRs. \[ER(dB)=10\log\left(\frac{P_{\min}^{1}}{P_{\max}^{0}}\right) \tag{11}\]1 Output performances of (a) ER and (b) CR under different input OSNRs. because the system is approaching its optimal performance under high OSNR conditions, and further increasing OSNR has a diminishing effect on reducing AM. In the low OSNR regime (OSNR < 12 dB), the value of AM is relatively large, and as input OSNR increases, the rate of decrease in AM is relatively fast.