Distributed surface plasma resonance optical fiber sensor and measuring method of liquid refractive index

The invention provides a distributed surface plasma resonance optical fiber sensor and a measuring method of liquid refractive index. The sensor comprises a step refractive index multimode fiber, a supercontinuum source and a spectrometer, which are located at both ends of the step refractive index multimode fiber. Two sensing areas are processed on the step refractive index multimode fiber; a first sensing area and a second sensing area region have different shapes, and are coated with nano metal films. The light source emitted by the supercontinuum light is coupled to the step refractive index multimode fiber and excites surface plasma resonance in the first sensing area, and the light intensity attenuates at the corresponding resonant wavelength; the light source emitted by the supercontinuum light reaches the second sensing area for the excitation of surface plasma resonance, and the light intensity attenuates at the corresponding resonant wavelength; the resonance wavelength generated by the first sensing area and the second the sensing area are different significantly, so as to realize distributed sensing. The invention has the advantages of small volume, low optical loss and simple structure, and has wide application prospect in the biomedical field.