Characteristic Research And Preparation Of Long Period Fiber Grating Based On Deep Modulation

In recent years,the development of sensors is changing with each passing day.More and more researchers are focusing on fiber grating sensors.Because of their small structure,simple preparation and good stability,various fiber grating sensors have been developed.In this article,three new types of long-period fiber grating sensors are prepared based on deep modulation,which are parallel inclined plane grid long-period fiber grating,V-groove long-period fiber grating and stepped long-period fiber grating.The strain sensing characteristics and temperature sensing characteristics were measured.The first step is a brief introduction to the coupled mode theory of the fiber.According to the coupled mode theory,the theoretical analysis of the axial strain and temperature characteristics of the long-period fiber grating is carried out,and the results are mutually verified with subsequent experimental results.In the second step,the single-mode fiber is etched into a parallel bevel grid long-period fiber grating with a high-frequency CO₂ laser equipment,the period is 8,the grating depth is42?m,and the grating period is 495?m.Then,the sensing characteristics of the parallel inclined plane grid long-period fiber grating were measured by the simultaneous measurement device of strain and temperature characteristics.Experimental results show that in the strain measurement range of 0??-425??,the strain sensitivity of the parallel inclined plane grid long-period fiber grating can reach 116 pm/??,which is two orders of magnitude higher than the strain sensitivity of the traditional long-period fiber grating.The third step is to simulate and analyze the long-period fiber grating structure of the parallel inclined plane grid.It is observed that when stress is applied,the deepest part of the grating etching has the highest equivalent stress distribution,and the effect of deep modulation on the grating sensor is obtained.The conclusion that performance has a great impact.The last step introduces two new types of long-period fiber grating sensors based on deep modulation,which are V-groove long-period fiber grating and stepped long-period fiber grating.The strain sensing characteristics and temperature sensing characteristics were measured.The experimental results obtained show that the strain sensitivity of the V-groove long-period fiber grating can reach 27.1 pm/??,and the strain sensitivity of the stepped long-period fiber grating can reach 27.4 pm/??,which exceeds the strain of the traditional long-period fiber grating.The sensitivity is more than ten times,and they all have good repeatability.This article is based on deep modulation,using high-frequency CO₂ laser writing method to write single-mode fiber,and prepared three new types of long-period fiber grating sensors.The etching depths of the three new types of long-period fiber grating structures are all up to40?m.These three kinds of long-period fiber grating sensors are not only simple in preparation method,but low in cost,and have high strain sensitivity,which are enough to be applied in real life.It also provides research ideas on deep modulation for follow-up researchers.