Research on liquid refractive index measured by the optic fiber surface plasmon wave sensor

By using an novel optical fiber sensing setup based on surface plasom resonance (SPR), several different kinds of liquids which have the same refractive index are measured in this paper. Influence of environment factors such as liquid refractive index, type and concentration of liquid on SPR effect are obtained by analyzing the SPR spectrum. Also, the relationship between the change of the liquid refractive index and the shift of location of resonance wavelength is discussed. However a basic principle of SPR effect for detection is that refractive index of the core of a fiber must be higher than that of the liquid. In order to enlarge application field of this sort of sensor, the structure of SPR probe is redesigned. The experiment and theoretical analysis show that this improved probe has the ability to extend the detection upper limit of refractive index and keep the toughness of optical fiber at the same time. This new technology opens up a new route to realize the real-time cure monitor and detecting of strain of composite material.