Research On Sensing Characteristics Based On D-type Long Period Fiber Grating

Long period fiber grating(LPFG)has been favored by many researchers since the last century,because it has advantages over other types of sensors.In some engineering and life fields,LPFG has a wide range of applications,including large construction engineering testing,life and health testing,etc.In this paper,CO₂laser etching technology is used to polish single-mode fiber,two novel long-period fiber grating sensors are proposed and their sensing characteristics are studied.In this paper,a D-type superstructure long period fiber grating(DS-LPFG)sensor is proposed,the period of the sensor is discontinuous instead of continuous,which makes the existence of multiple resonant peaks in the transmission spectrum instead of one,by comparing the strain sensing characteristics of several parameters DS-LPFG,a good performance DS-LPFG is selected.The sensing characteristics of DS-LPFG in the field of stress and temperature measurement are studied,the experimental results show that the resonant wavelength of the resonant peak has a good linear relationship with the stress and temperature and moves towards the long wave direction within a certain range of axial stress and temperature.The resonant wavelengths of the two resonant peaks have different responses to the changes of temperature and strain,which provides the possibility for simultaneous measurement of the two parameters.The magnitude of the strain and temperature discrimination can be calculated by using the matrix measured simultaneously.A new D-type chirped long period fiber grating(CDS-LPFG)is proposed by adjusting the spacing between two D-type grooves of the DS-LPFG.In this paper,two kinds of parameter CDS-LPFG structure are designed,and its sensing characteristics of axial strain,bending and temperature are explored.The experimental results show that the amplitude of the three loss peaks of CDS-LPFG has a good linear relationship with the change of axial stress,and the position of resonant wavelength of the loss peaks do not shift with the increase of stress.The response of resonant wavelength to bending and temperature is quite different,so CDS-LPFG can be used for the simultaneous measurement of bending and temperature.Different stresses are applied to the DS-LPFG and different weights are hung to indicate different stresses.With the increase of stress,the bending sensitivity does not change significantly.When the stress is applied to a certain point,a new resonance peak appears in the spectrum,and the bending sensing characteristics of the derived peak are studied.The derived peak and the inherent resonance peak of DS-LPFG can be used in the study of simultaneous bending-temperature measurement.