Sensing Characteristics Analysis Of Flexible Encapsulated DBR Fiber Laser

With the requirements of integration,miniaturization and networking of sensing technology,optical fiber sensing technology has obtained widely attention for its small size,light weight,immunity to electromagnetic interference,multiplexing ability,good long-term stability,etc.As an advanced optical active device,fiber laser not only has the features of traditional passive fiber components,but also has the characteristics of narrow linewidth,high signal to noise ratio,and being able to realized high sensitivity sensing.However,since it is easily broken,which limits its application in practice.Flexible encapsulation can not only protect and sensitize fiber laser,but also be applied to special environment.Based on this background,this paper proposes a polymer-coated distributed Bragg reflector(DBR)fiber laser,and discusses its sensing characteristics from the view of simulation and experiment.Firstly,this paper reviewed the history of fiber laser and encapsulating technology.Secondly,this paper introduced FBG sensing technology,the structure and fabrication of DBR fiber laser,and sensing principles.Then we summarized several commonly used encapsulating technologies and polymer-coated FBG sensors.Finely,we analyzed the influence of polymer encapsulation on fiber laser from the view of simulation and experiment.In terms of simulation,we established the sound-structure coupling model based on the theoretical background of underwater acoustic sensing by using COMSOL Multiphysics.The sensitivity gain was about 110 dB with respect to bare fiber,and the hydrophone sensitivity spectrum exhibited characteristic resonances.We also carry out a parametric analysis by varying the geometrical and mechanical properties of the coating.In terms of experiment,we coated the fiber laser with epoxy resin,and studied its response to ultrasound and temperature.For ultrasound,the fiber laser could increase the sideband amplitude by about 5dB,and this enhancement was independent on the frequencies and amplitude of ultrasonic signals.For temperature,the sensitivity of polymer-coated fiber laser was 0.31095MHz/? between 25? and 70?,and was 4 times of bare fiber.