Interferometer absolute displacement demodulation system and method using gas absorption spectrum reference

The invention discloses an interferometer absolute displacement demodulation system and method using gas absorption spectrum reference, and the system comprises a scanning laser, an optical fiber isolator, an optical fiber coupler, an interferometer, a signal detector, a reference detector, a signal amplifier, a microprocessor, and a gas reference gas chamber which are connected in a light path. The gas reference gas chamber is filled with reference gas with an absorption peak in a wavelength scanning range of the scanning laser; according to the calibration method, an absorption spectrum of reference gas with an absorption peak in a wavelength scanning range of a scanning laser is used as an absolute spectrum reference position, and conversion from a time axis to a wavelength axis or a phase axis is carried out by combining a fixed wavelength and a spectral line half width of an absorption spectral line or a wavelength interval of two absorption spectral lines. And the absolute value measurement of the cavit