(1) Determine the number of decomposition layers:In the process of optical fiber communication, bothsignal and noise have modulus maxima, and theirmorphology in the wavelet domain is different. Theamplitude and density of noise decrease with the increaseof the number of layers. The trend of signal modulusmaxima is opposite. Therefore, combining with thisfeature, it can be inferred that whether each layer afterwavelet decomposition is dominated by noise, so as to geta reasonable number of decomposition layers.