Mode Simulation And Absolute Refractive Index Measurement Of Tilted Fiber Bragg Grating

Sensor otten reters to a kind of technical device which can monitor the detected quantity and take the information we want to obtain.Sensor technology can be used to detect the change of the detected quantity,and it has been used to detect the physical and chemical parameters such as strain,temperature,humidity,wind force,ion concentration,etc.However,most of these sensors use electric signal transmission,with high transmission loss and easy to be interfered by the outside world.The emergence of optical fiber provides a good medium for information transmission.In recent years,more and more research teams have begun to study the transmission characteristics of optical fiber,and the optical fiber sensing is becoming more and more popular.In the optical fiber sensing,fiber grating sensor has been applied to many fields because of its excellent sensing characteristics.As an important part of FBG sensor,tilt fiber grating has changed its properties because of the angle between the grating and the fiber cross section.Compared with FBG,there are not only core modes,but also a series of cladding modes.And this series of cladding modules also have many different properties.Many research teams have carried out a lot of research according to the different properties of their cladding modules,so that they can be applied to many different fields.So we study and simulate the mode of tilt fiber grating,we can understand the transmission characteristics of tilt fiber grating fundamentally,so that we can deepen our understanding of it.In order to understand the sensing principle of the tilted fiber grating sensor in detail,we start from the electromagnetic characteristics of light,solve the optical mode existing in the fiber,analyze the characteristics of its mode,and couple each cladding mode with the base mode to get the coupling coefficient and the spectrum diagram.In the process of studying the tilted fiber grating,we found that the cladding mode is sensitive to the change of refractive index of the external environment.Different wavelength modes correspond to a certain effective refractive index,and the mode cutoff occurs in the measurement range,so we can measure the absolute refractive index of the external boundary.