Research On Distributed Feedback Narrow Linewidth Fiber Laser And Its Sensing Characteristics

Due to its advantages of narrow linewidth,low noise and good coherence,narrow linewidth fiber laser can be widely used in coherent optical communication,high sensitivity optical sensing and other fields.In recent years,it has gradually become one of the hot research directions of fiber laser.As a kind of optical fiber laser cavity fiber laser,distributed feedback fiber laser(DFB-FL)possesses characteristics such as single frequency and single mode,low noise,narrow linewidth and small size,so it is very suitable for detecting physical quantities such as strain,acceleration and vibration sensor,DFB-FL has a high sensitivity,resistance to electromagnetic interference,easy to form arrays for multiplexing,it has been successfully used in the optical fiber hydrophone system,seismic wave detection,etc.The light output characteristics and encapsulation structure of DFB-FL determine the precision and sensitivity of the sensor.Therefore,it is of great significance to study and optimize the fabrication technology of DFB-FL,the performance testing technology of DFB-FL and the structural design of the sensor.The main research results of this paper are as follows:1.Based on transfer matrix theory,coupled mode theory and the erbium ions level rate equation theory,systemic simulation analysis of the phase-shift fiber grating and DFBFL output light field features,mainly includes the amount of phase shift and phase shift position,grating length and refractive index modulation depth of phase-shift fiber grating parameters,such as passive transmission spectrum and DFB-FL out the influence of the optical properties.2.Setting up the fiber grating inscribing system based on the exposure of Kr F excimer laser and phase mask template technology,the phase mask template scanning method was adopted to realize the manufacture of ?-shifted fiber grating in different active optical fiber,and study the different refractive index modulation depth of the DFB-FL output spectral characteristics,the influence of narrow linewidth output is stable.3.A DFB-FL system based on phase-shifted fiber Bragg grating was built,and the laser output characteristics such as laser pump threshold,efficiency,linewidth,noise characteristics and stability were studied.The pump threshold power of the DFB-FL is110 m W,pump conversion efficiency is 0.074%,the laser linewidth of 3d B is 15 k Hz,the laser linewidth was compressed by means of self-injection mode locking,and the 3d B linewidth was 4.7k Hz after compression.The saturation output power of the laser can be improved by water cooling.4.The temperature and sound sensing characteristics of DFB-FL were experimentally studied,and the results showed that the temperature sensitivity of DFB-FL was9.28pm/?,and the sound pressure sensitivity of DFB-FL was 439.07 m V/k Pa at 1MHz sound frequency,nearly 40 d B times higher than that of the traditional piezoelectric hydrophone.The minimum detectable sound pressure was 15.5m Pa/?Hz,and the resolution was nearly 230 times higher than that of the traditional piezoelectric hydrophone.A DFB-FL sensor package structure was designed by simulation.The analysis results show that the package structure can improve the sensor sensitivity by about 2 orders of magnitude.