Research On Temperature And Pressure Sensing Characteristics Of Optical Fiber Fabry-Perot Sensors

Fabry-Perot interferometer is a multi-beam interferometer composed of two reflecting surfaces.When the effective length of the interferometer or the refractive index of the medium changes,the interference fringe will move.Optical fiber F-P sensor is a device that uses this theory to detect parameters such as temperature,pressure,refractive index and so on.It has the advantages of simple structure,small size,high sensitivity,and high anti-interference.At present,it has been used in aerospace,road bridges,health monitoring,environmental testing,and petrochemicals.Optical fiber F-P sensor is being more and more important.The optical fiber F-P instrument is currently the most widely used optical fiber sensor and one of the most widely studied optical fiber sensors in the scientific research field.The four types of interference fiber sensors and fiber gratings sensors are introduced and analyzed,and the typical structures corresponding to these five fiber sensors are introduced.This paper summarizes the domestic and overseas research progress of optical fiber F-P sensors,analyzes the advantages and disadvantages of various structures,This paper presents three types of optical fiber F-P interferometers with different structures.The temperature and pressure sensing characteristics of three kinds of sensors are verified theoretically and experimentally1.The principle and characteristics of femtosecond laser micromachining are introduced in chapter three.A cascaded fiber F-P interferometer is made by using femtosecond laser micromachining.One of the two F-P interferometers is air F-P cavity formed by laser processing and the other is a fiber F-P cavity formed by a section of optical fiber.The F-P cavity formed by the optical fiber can be used as temperature sensor which can bear up to 1100 ?.The temperature sensitivity is 14.83 pm / ? at 1590 nm.The air F-P cavity can be used as a pressure sensor,and the air pressure sensitivity is 3.897 nm/MPa at 1550 nm.2.The femtosecond laser is used to modify the core of the single mode fiber,and the F-P interferometer formed by the remained fiber is used for temperature sensing up to 1100 ?.The temperature sensitivity is 14.97 pm / ? at the wavelength of 1590 nm.The production process is very simple.This sensor has some advantages in applications.3.By increasing the length of the hollow fiber in a common single mode fiber-hollow fibersingle mode fiber structure,the divergence angle will cause longitudinal F-P interference on the wall of hollow fiber,which caused the envelope of the spectrum.Temperature and pressure sensing were performed by using lateral and longitudinal interferences,respectively,with sensing sensitivities of 0.629 pm / ?,-3.73 nm / MPa,26.1 pm / ?,and 4.08 nm / MPa,respectively.Temperature and pressure are demodulated at the same time through a temperature-pressure sensitivity matrix.The dual-parameter sensing solves cross-sensitivity of temperature in the measurement of pressure.