Strain-type Tunable Fiber Laser

Tunable fiber laser is a key device in optical communication and fiber sensing system.It can achieve high-intensity lasing output and large-scale tuning range which is the hot issues in recent research in this field.In this paper,the ring cavity erbium-doped fiber laser(EDFL)is used as the research object,and the mode interference filter/ Sagnac filter are used as the tuning element,by applying axial and tangential strains,continuous tuning of wavelengths of 4.7nm and 12.4 nm was achieved.The main research work is as follows:(1)Using the OptiSystem software,a ring cavity fiber laser simulation model was constructed,and the correspondence between the output optical power and pump power,the length of erbium-doped fiber(EDF),and the splitting ratio of the coupler was analyzed.A ring cavity EDFL experimental test system was constructed based on the optimal splitting ratio and the length of EDF.(2)The Mach-Zehnder(MZ)interference filter was analyzed and prepared,and the fiber laser system based on the MZ interference filter is constructed.The experimental results show that the fiber laser based on MZ interference filter is not convenient for single longitudinal mode laser output and has low stability.A fiber laser system based on a multimode interference(MMI)filter was further constructed,and the optimization parameters and output spectrum are optimized,a high intensity and stability output of lasing wavelength was obtained.The MMI filter structure is placed on a microdisplacement platform,and axial strain is applied to carry out the experimental study of wavelength tuning of the fiber laser.The experimental results show that the lasing wavelength is blue-shifted from 1559.3nm to 1554.6nm in the range of 0?3000??,and the tunable range is up to 4.7nm.At the same time,during the tuning process,the extinction ratio of the laser wavelength is 37.74 dB,and the line width is 0.144 nm.(3)In order to develop the tunable range,the interference principle and tangential strain tuning principle of Sagnac filter based on polarization-maintaining fiber are theoretically analyzed,and the length of polarization-maintaining fiber and the output spectrum of the filter were optimized.Furthermore,an experimental study of tunable fiber laser with tangential strain based on PMF-Sagnac filter was carried out.The experimental results show that by fine-tuning the polarization-maintaining controller,the lasing wavelength can obtain a good single longitudinal mode output with a line width of 0.14 nm.Applied tangential strain in the range of 0?314rad/m,continuous tuning of 12.4nm can be achieved.And the laser wavelength and power stability are limited to ±0.046 nm and ±0.42 dB,respectively.