## 3 Results and Discussion
### The UWOC Application  
To test the performance of data transmission, the waveform of obtained data from the 12-bit ADC was recorded and marked as \"received_data\" as shown in Figure 5a. A binary digital waveform was obtained via voltage comparison and named \"decided_data\". Due to the noise of the PDs and interferences from the environment, decision errors may occur at certain points where the voltage signal fluctuation happens in the level close to the decision threshold, leading to glitches in the \"decided_data\" waveform as highlighted in Figure 5a by red frame. This kind of glitch can seriously reduce the robustness of a UWOC system. They can cause data decision errors when they appear within data bits, and cause the premature reception or misalignment of subsequent data when they occurs outside of data bits. To deal with this issue, a filtering operation was introduced by caching the waveform data for one clock cycle. The \"0/1\" switching is effective only when the later received data match with the cached data, otherwise they would be treated as jitter. This operation can filter out glitches lasting for one clock cycle, reducing the decision error rate and improving communication quality. As shown in Figure 5a, the glitch in the \"decided_data\" was removed, and correct data was obtained in \"final_data\". The bit error rate (BER) is a key performance parameter of a communication system. Figure 5b shows the BER of transmitting random data at different data transmission rates for both perovskite PDs and silicon PDs. The BER of perovskite PDs exhibits a steeper curve compared to the silicon PDs, indicating that the perovskite PDs show more stable communication performance before reaching their frequency limit (6.25 Mbps), although silicon PDs display better performance in their high data-transmission rate. The BER of transmitting repeated \"01\" for the frequent on/off switching scenario is shown in Figure 5c. It indicates that the perovskite PD demonstrates better stability compared to the silicon PD in frequent \"01\" transitions. An analysis of data errors shows that the errors of silicon PD are mainly from the misinterpretation of \"0\" as \"1\", for example, the number 85 (\"01010101\") being misinterpreted as 87 (\"01010111\") or 255 (\"1111111\"). In contrast, the errors in the perovskite PD tend to be missing data packets or missing some data points, which is easily observed in subsequent image transmissions. To better understand the difference in BER between perovskite PDs and silicon PDs, the waveforms of perovskite PDs and silicon PDs under the illumination of high-frequency optical signals were investigated by a digital oscilloscope. As shown in Figure 6a,b, the silicon PD exhibits a narrower response than the perovskite PD. The ratios of time spans for high voltage levels and low voltage levels were calculated, which theoretically are one due to the on/off of optical signals occupying equal time spans. The ratio of the silicon PD is only 0.29, far less than that of the perovskite PD (0.71), indicating that the perovskite PD has fewer chances to cause misinterpretation. The background currents and noise currents were also studied under different environment illuminations, which were simulated using a Xe Lamp and a neutral-density filter. As shown in Figure 6c,d, perovskite PDs exhibit lower background currents and noise currents in the environment light condition, even though the silicon PD has lower intrinsic noise and  
Figure 5: (**a**) The waveform of received signals in the raw, decided, and final states. The red frame highlights the glitches; the BER of PDs for different transmission rates of (**b**) random data and (**c**) regular \"01\" data. dark current. The lower noise of the perovskite PD should be the reason that contributes to the stable communication performance.