The invention relates to a method and
system for identifying a modulation format based on optical signals in the field of
optical fiber communication. The method includes the steps that a TDC exerts certain dispersion values on input optical signals to be identified and then outputs the optical signals, after passing through an
optical amplifier, the optical signals are injected into a non-linear
power transfer function NPTF generating module, and a
optical power meter measures
signal average power of the output end of the non-linear
power transfer function NPTF generating module; a control and
digital signal processing module drives the TDC to generate a series of dispersion values and records each dispersion value and the
signal average power, corresponding to each dispersion value, of the output end of the NPTF generating module, and the dispersion values and corresponding
signal average power are stored as a dispersion-signal average power measured value array. Matching is carried out among various dispersion-signal average power samples with known modulation format signals and the dispersion-signal average power measured value array, and the modulation format of the best
matched sample is discriminated as the modulation format of the input signals. The method and
system for identifying the optical
signal modulation format does not need any
prior information at work, is suitable for signals with various modulation formats and speed and has the advantages of being simple in structure and high in
cost performance.