Research On Tunable Fiber Laser Based On Self-imaging Effect And Its Sensing Application

The phenomenon that an electromagnetic field can reproduce itselfperiodically along the propagation direction called the self-imaging effect. In thispaper, the self-imaging effect in the multimode fiber is investigated and analyzed indetail. In accordance with the self-imaging effect, a simple and inexpensive opticalfiber filter is fabricated. And the filter is applied into the optical fiber ring cavity tomanufacture a tunable fiber laser based on self-image effect. The output laserwavelength of this tunable fiber laser is determined by self-image effect. Externalfactors which can affect the self-image effect cause the laser wavelength shift. Basedon this mechanism, we have designed a fiber laser sensor based on self-image effect,and a number of external factors have researched from sensing perspective. Excepthas high sensitivity as traditional interferometer, the fiber laser sensor based onself-image effect also has the advantages like a single wavelength output, highresolution etc. In measurement, many laser sensors can be detected by a spectrometer,or directly detected with a wavelength meter and other instruments, which can reducecosts. So the fiber laser sensor based on self-image effect has good prospects for thestudy and application. The concrete research content is as follows:1. In this paper, the development process of self-image effect is described byreferring to the relevant literature. The research status of the optical fiber sensors andoptical fiber laser based on the self-imaging effect is expounded emphatically.2. The basic theory of self-image effect is analyzed. The wavelength correspondingto the self-image effect peak is obtained through theoretical derivation. SoftwareRsoft is used to simulate and analyze the self-image effect peak. According to theprevious derived equation, the decisive factors which deciding the self-image effectpeak are simulated, such as the length of multimode fiber, the diameter of multimodefiber, the refractive index outside of the fiber, etc. The function of filter based onself-image effect is also analyzed, which provides a theoretical basis for the laser andverify the fiber laser sensor based on self-image effect is possible.3. To verify the theoretical analysis and software simulation is correct, the filterbased on self-image effect is analyzed experimentally. And the filter is applied intothe optical fiber ring cavity to use the function of filtering to manufacture a tunable fiber laser based on self-image effect. The working principle of the laser is alsointroduced.4. The tunable laser (fiber laser sensor) based on the self-image effect is to strain,bend, refractive index, salinity, liquid level, temperature, humidity, and theparameters for the sensor aspects of experimental research, the experimental methodand principle of the experiment are introduced.In this paper, the fiber laser sensors based on self-image effect were studied by theory,simulation and experiment. The work carried out can promote the development ofoptical fiber laser sensor. What’s more, it also has a good reference value for thetuning method of tunable laser base on self-image effects.