Distributed Transverse-stress And Strain Fiber Optic Sensing And Application Exploration Of Composite Material Bending Measurement Using PA-OFDR

This paper uses the polarization analysis optical frequency domain reflection(PA-OFDR)technology that introduces the polarization state generator(PSG)and polarization state analyzer(PSA)modules into the optical frequency domain reflection(OFDR)technology,and mainly studies the characterization of performance parameters of distribution transverse-stress and strain optical fiber sensing based on PA-OFDR,simultaneous measurement of two parameters of transverse-stress and strain,and application exploration of bending measurement of embedded optical fiber composite materials.The main content and innovation are as follows:1.Research the performance of PA-OFDR distributed transverse-stress sensing.Transverse-stress was applied and measured at 10 different positions on the optical fiber at the same time,and the birefringence distribution information along the optical fiber was obtained,which verified the distributed transverse-stress measurement capability of the sensor system and measured the transverse-stress induced birefringence coefficient:9.177×10^-8.Through experiments of different transverse-stress conditions,it is verified that the minimum measurable transverse-stress of the sensing system is 0.661 N/m,the sensing spatial resolution is 3.7 mm,and the maximum sensing distance is 103.5 m2.Research the performance of PA-OFDR distributed strain sensing.Perform cross-correlation calculations on the Rayleigh scattering distribution measured before and after the strain to obtain the strain occurrence location,and obtain the Rayleigh scattering distribution displacement information-optical fiber deformation information by intercepting the data through the sliding window and performing cross-correlation calculations,and the fiber strain was obtained by differential calculation on the optical fiber deformation information.The accuracy of the strain measurement of the sensing system is verified by a reading microscope and a cantilever beam of equal strength.At the same time,it is known that the strain measurement fluctuation gradually decreases with time,and the fluctuation size is only 5.92??after 60 minutes,and the measured strain measurement resolution is 11.54??.By setting two or more identical strain zones on the optical fiber and measuring,the distributed strain measurement capability of the sensing system is verified,and the uncoated,common coating(polyacrylate),and gold coating(polyimide)are compared.The amount of strain measured by the optical fiber under the same conditions shows that the amount of strain obtained by the gold coating and the uncoated layer is relatively consistent,and the amount of strain obtained by the ordinary coating layer is 4.27%smaller.3.The feasibility of distributed simultaneous measurement of transverse-stress and strain based on PA-OFDR technology is preliminarily verified.Under different strain variables,the same transverse-stress induced birefringence coefficient is obtained,which verifies that the transverse-stress and strain do not influence each other.4.The ability of PA-OFDR technology to detect bending deformation of composite materials is preliminarily verified.By measuring the change of the birefringence along the fiber,the stress change in the carbon fiber composite plate can be reflected by bending the carbon fiber composite plate with different radius.ANSYS software is used to simulate the bending and deformation of the composite with embedded fiber,and the variation trend is consistent with the experiment.