Study On The Fiber Laser And Fiber Sensor Based On Fiber-optic Interference Technology

Fiber-optic interference technology has been widely used in fiber-optic communication, fiber-optic sensing, structural-health monitoring and aerospace, due to the advantages including immunity to electromagnetic interference, corrosion resistance, high sensitivity,simple structure and compatibility with fiber.Fiber-optic interferometer usually serves as the comb filter in the tunable multiwavelength erbium-doped fiber laser(MEDFL). While none of the modern methods can support four types of tunable operations for dozens of lasing line with the same resonator structure: channel-spacing, peak-location, spectral-range, and wavelength-number. Therefore, we have proposed and demonstrated a MEDFL based on tunable Mach-Zehnder interferometer(MZI) and intensity-dependent loss(IDL) modulation. The wavelength-number and the spectral-range of the lasing lines can be accurately controlled by IDL modulation in the laser cavity, enabled by a power-symmetric nonlinear optical loop mirror. The channel-spacing and peak-location can be controlled by changing the working state of MZI. In addition, fine control over the wavelength-number at fixed spectral-range is realized by simply adjusting the pump power. More important, the tunable operation process for every type of specific parameter is individual, without influences for other output parameters.Besides, the fiber-optic interferometer can be used to monitor the changing parameters such as temperature, pressure, ultrasound, strain, refractive index, humidity and gas concentration. In the practical measurement, a high sensitivity of the sensor is also attractive. So we proposed three kinds of high sensitivity fiber sensor based on Fabry-Perot interferometer(FPI).An ultra-high sensitivity open-cavity FPI gas refractive index sensor based on Vernier effect is proposed and demonstrated. The reflected beam from the end face of reflection fiber, which would consequently increase the difficulty and the costs of fabrication, is used to generate the Vernier effect. Experimental results show that the proposed sensor can provide an ultra-high RI sensitivity of 30899 nm/RIU.Based on the non-uniform fracture characteristics of photonic crystal fiber, a novel high sensitivity FPI strain sensor is proposed and demonstrated. In this work, a FPI cavity with a length of 3.43 μm and a high strain sensitivity of 42.27 pm/με was achieved. The sensitivity provided is comparable with the existing technology.At last, by improving the fabrication mechanics of concave-core photonic crystal fiber, we have proposed and fabricated a novel open-cavity FPI refractive index fiber sensor. The proposed sensor shows good performances, such as high RI sensitivity, linear RI response, low temperature cross-sensitivity and fast response.These results in our work have provided the significant theoretical support for modern fiber-optic laser source and fiber-optic sensing. It is meaningful to increase the development of fiber interference technology in fiber frontier science.