In order to deeply understand the performance of optical signal transmission, modulation, demodulation, and improve the transmission rate, distance, and stability of optical communication systems, a spectral feature extraction based optical signal characteristic analysis method is proposed. This method establishes an optical signal detection channel consisting of a coupler, reflector, and fiber Bragg grating sensor array. After obtaining the optical field intensity and optical communication signal during optical signal transmission through this channel, Fourier transform is performed on it to obtain the frequency spectrum of the optical signal. Then, linear frequency modulation transform and window setting are used to detect single frequency components from the frequency spectrum of the optical signal, extract the frequency spectrum characteristics of the optical signal. Based on the frequency spectrum characteristics of the optical signal, a three wave coupling equation of the optical signal is established. After solving this equation, the pump light frequency, scattered light power, and other characteristics in the optical signal characteristics are obtained. The experimental results show that this method can effectively obtain the frequency spectrum of optical signals, extract spectral features from this frequency spectrum, and analyze the scattered light intensity frequency of optical signals under different pulse widths, with strong applicability.