Minitype F-P reflective index sensor of full optical fiber ring-type reflecting surface structure

[0020] See figure 1 , Shown in the figure is the sensor structure of the present invention, it is composed of ordinary single-mode fiber 1, large-core hollow-core fiber 2 and the center of the optical fiber 3, ordinary single-mode fiber 1, large-core hollow-core fiber 2. The fiber 3 with a through hole in the center is fusion spliced ​​in sequence, and the core of the large-core hollow fiber 2 and the fiber 3 with a through hole in the center are connected;

[0021] The core (ie, FP cavity) of the large-core hollow-core fiber 2 is closed by the ordinary single-mode fiber 1 and the fiber 3 with a through hole in the center, respectively. The core of the large-core hollow-core fiber 2 (2 in the figure) -1) can only communicate with the external environment through the core of the optical fiber 3 with a through hole in the center (point 3-1 in the figure), and the optical fiber 3 with a through hole in the center should be short enough to make the external fluid (gas, Liquid) can easily enter the core of the large-core hollow-core fiber 2 to change the refractive index of the FP cavity. At the same time, the outer diameter of the optical fiber 3 with a through hole in the center is smaller than that of the large-core hollow-core optical fiber 2, otherwise it cannot be formed on the contact surface of the large-core hollow-core optical fiber 2 and the optical fiber 3 with a through-hole in the center. The core diameter of the optical fiber 3 with a ring-shaped reflecting surface and a through hole in the center should be smaller than the core diameter of the large-core hollow-core optical fiber 2 (see figure 2 , 3 ).

[0022] Another key point of the present invention is the manufacture of the sensor. The specific steps have been described in detail in the content of the invention, and will not be repeated here. After the sensor is manufactured according to the method of the present invention, other external equipment is required to be combined with it. Complete measuring device, the structure of the measuring device is as Figure 4 As shown, it consists of a broadband light source 4, a 1×2 coupler 5, a miniature FP refractive index sensor 6 with an all-fiber ring-shaped reflective surface structure, a spectrometer 7 and a computer 8; among them, the broadband light source 4 is connected to the 1×2 coupler One end of 5 and the other end of the coupler 5 are connected to a miniature FP refractive index sensor 6 with an all-fiber ring-shaped reflective surface structure to form a reflection interference spectrum. The 1×2 coupler 5 is connected to the spectrometer 7, the computer 8 and the spectrometer 7 Communication connection to process data.

[0023] Place the refractive index sensor in the gas or liquid that needs to be measured. The gas or liquid can easily enter the Fabry-Perot cavity through the small hole of the optical fiber 3 with a through hole in the center. Due to the micro-FP refractive index of the all-fiber ring-shaped reflective surface structure adopted The length of the Fabry-Perot cavity of the sensor 6 is in the micron level, and the gas or liquid outside the cavity exchanges with the gas or liquid in the cavity fast, so the miniature FP refractive index sensor 6 with the all-fiber ring-shaped reflective surface structure will quickly respond to the measured object The refractive index.

[0024] The signal flow process of the measurement system is: the broadband light source 4 outputs a laser with a certain bandwidth wavelength (usually a C-band laser, 1520nm~1570nm), enters 1×2 couplers 5, and then enters the miniature of the all-fiber ring-shaped reflective surface structure The reflection interference spectrum formed by the FP refractive index sensor 6 enters the spectrometer 7 through 1×2 couplers 5, and the spectrometer 7 stores the reflection interference spectrum in the computer 8 through a communication connection, and then processes the data.