Analysis Of Mechanical Properties Of Multimode Fiber Optic Sensors And Its Application

Fiber Bragg grating are widely used in the field of architecture and civil engineering,and requires the demodulator of precision spectrometer.However,the research of pressure sensing based on the straight structure fiber is less.In this paper,we explore the feasibility of single mode fiber and multimode fiber as pressure sensor by using the straight structure of the fiber itself.First the elastic mechanical model and the basic equation of the straight structure of the fiber is established.ANSYS software is used for the analysis of stress and strain distribution and the results show that the stress and strain of load section fiber are linearly related to load of 0g-300 g with the single-mode fiber,the multimode fiber of 50?m core diameter and multi-mode fiber of 105?m core diameter.In one words,the single-mode fiber and the multi-mode fiber can be used for the measurement of load on fiber.In the experimental process,the straight structure fiber is used as the test unit and the change of the optical power is measured and analyzed during the pressure loading.The experimental results show that:1)There is a linear relationship between the output optical power of the single-mode fiber with the pressure loading process from 0g to 400 g,the linear correlation coefficient R2=0.8995;but the linear correlation coefficient R2 of the pressure unloading process from 400 g to 0g is 0.1105,that means the single-mode fiber is not suitable for load detection.2)The linear correlation coefficient R2 of the pressure loading process from 0g to 400 g is 0.9117 for the multi-mode fiber;and the linear correlation coefficient R2 of the pressure unloading process from 400 g to 0g is 0.7061,that means the multimode fiber is suitable for load detection.3)The final selection of the straight structure fiber is used to detect the load by comparing the straight structure fiber,the bent structure fiber and the supporting structure fiber.The results show that the load length should be greater than 4.5 cm.The response time of detection of the loading process is faster than the recovery time of unloading process;the smaller the load,the shorter response time and recovery time;the response time is 2s and the recovery time is 10 s to the typical load value 100 g.Finally,the correlation between the optical power and the load of the viscoelastic material collagen under different pressure is detected by using multimode optical fiber as the pressure sensor,and the correlation coefficient R2 is 0.9457.So it can be concluded that the straight structure multimode fiber can be used as a pressure sensor.But to obtain good repeatability,the multimode fiber should be industrial products,avoid repeated installation of connection of light source or power meter,and ensure the load acts perpendicular to the fiber.