DEVELOPMENT OF A CONTROL AND INTERROGATION SCHEME OF A FIBER-OPTIC BEND SENSOR BASED ON DOUBLE CLADDING FIBER
The control and interrogation scheme of the fiber optic bend sensor was developed and implemented. The structure of the sensor is formed by inserting a section of SM630 fiber with double cladding between standard SMF-28 single-mode fibers. The operating principle of the sensor is based on conversion between core and cladding modes. The modes are coupled at the junction of the fibers with different refractive index profiles. Two laser diodes with the wavelengths of 1328 and 1545 nm are used for sensor interrogation. At these two wavelengths, the dependences of fiber transmittance on bending are significantly different. A microcontroller is used to control and collection data from a photodetector. The article shows that the proposed and implemented scheme allows the sensor to measure bends with curvature radii from meters to 26 cm with a measurement error less than 1%.