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

Abstract

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.

Description

technical field [0001] The invention relates to an optical fiber sensor, in particular to a distributed SPR optical fiber sensor mainly used for sensing and measuring environmental refractive index, solution concentration and the like. The invention also relates to a method for the optical fiber sensor to measure the refractive index of a liquid. Background technique [0002] Surface Plasmon Resonance (SPR) is a physical phenomenon produced by the interaction of light with the conductive medium at the interface during the total reflection process. In the process of total reflection, light will pass through the optically sparse medium for about one wavelength, then propagate along the interface for about half a wavelength, and then return to the optically dense medium. The light wave passing through the optically sparse medium is called an evanescent wave. The evanescent wave excites the conductive medium to generate surface plasmon waves. When the frequency of the evanescen...

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Problems solved by technology

With the diversification of the types and characteristics of the target parameters to be measured, the conventional single-stage SPR sensing mechanism has gradually been unable to meet the needs of actual detection.

2005 Homola et al proposed a prism-based distributed multi-channel SPR sensor (J.Homola.Multi-analyte surface plasmon resonance biosensing[J].Methods,2005,37(1):26-36), which can simultaneously monitor multiple analysis However, there are disadvantages such as large volume, high cost, and not easy to carry

[0004] In 2012, Y.Yuan et al. proposed a distributed SPR sensor by changing the metal film thickness (Y.Yuan, L.Wang, J.Huang. Theoretical investigation for two cascaded SPR fiber optics sensors[J].Sensors and Actuators B : Chemical, 2012, 161(1): 269-273), but it is only analyzed theoretically. In actual operation, the optical fiber is easy to be broken because the fiber size is too thin, and this method realizes distributed SPR by changing the metal film thickness The two resonance valleys produced by the sensor are too close to easily superimpose into one illegible

In 2015, Zhao Enming and others successfully developed a distributed SPR optical fiber sensor using dual-core optical fiber, and proposed the invention patent of "distributed surface plasmon resonance optical fiber sensor" (patent application number: 201510400263.6), which was processed on the dual-core optical fiber Multiple sets of V-shaped grooves realize distributed sensing, but because the core size is too thin, high processing accuracy is required and light injection is difficult. In addition, the depth of the SPR resonance valley is too shallow due to the small sensing area, which is not easy to identify

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