Measurement Of Liquid Refractive Index Based On Wavelength Encoding

The system of the optic fiber Fabry-Perot and Mach-Zehnder measuring refractive index of liquid based on the principle of Fiber Optic Filter is separately designed in this paper. It has more advantages, such as simple structure, low cost and high anti-interference. It can be manufactured and put into use in many fields.The principle of Fiber Optic Filter used for measuring refractive index of liquid is analyzed in theory. Basing on the principle of interferometric filtering to broadband light source, a new method which can realize to apply separately Fiber Optic Fabry-Perot Filter and Fiber Optic Mach-Zehnder Filter for measuring refractive index of liquid is put forward and the system with the optic fiber Fabry-Perot and fiber Mach-Zehnder structures which measures refractive index of liquid is designed. It primarily consists of light source, Optical Spectrum Analyzer, fiber coupler, coated pigtail, fringe and porcelain bushing. The designing focal point of this paper is the refractive index of liquid sensors separately basing on the fiber Fabry-Perot and the fiber Mach-Zehnder structures. The principle of them is the same. It is that changing optical path difference of interferometric light by filling liquid so that can change the output spectrum and calculate the refractive index of liquid by detecting the change of the stripe peaks. It is seen that the system has the ability of high anti-interference. Because it is to measure the refractive index of liquid by encoding to the transmission peak's wavelength in the system, and the change of light intensity can only change the amplitude of output spectrum and can't impact reading the stripe peaks.