The Studies On Tellurate Glass Based Lensed Fiber Fabry-perot Senser And Its Application

Compared with all kinds of traditional sensors,optical fiber sensor takes light as the carrier of sensitive information and optical fiber as the medium to transmit sensitive information.It has the characteristics of optical measurement and optical fiber.Up to date,the optical sensors are highly demanded and are featured with the good performances in electrical insulation,anti-EMI,non-invasive detection,high sensitivity,anti-corrosion,explosion-proof and so on.Among the optical sensors,the Fabry-Perot resonators are one of the successful devices due to its small foot-print,robust structure,high sensitivity,and the potential applications in the special areas like the nuclear radiation zone,biomedical sensing,and medical treatments.In this thesis,we will introduce the research backgrounds and applications for the Fabry-Perot interferometers(FPI)as well as the working principles in the beginning part.Based on these,we have designed and fabricated the fiber FPI sensors using tellurite glass,which has a renowned transmission window at the mid-infrared wavelength bands.In applications,we have also successfully achieved and investigated the high-sensitivity temperature sensors,liquid index sensors,and displacement sensors.The innovations of our works include(1)combing the spherical high-index tellurite-glass Fabry-Perot cavity and the Ge-diffused core in the single mode fiber to substantially improve the Q factor to reach to high extinction ratios and(2)shaping the wavefront of the standing waves in spherical cavity to achieve high accuracy displacement sensing.The contents of this thesis include the following aspects:1.Based on the Ge-dopant diffusion in optical fibers and the tellurite-glass microcavity fabrication methods,several fiber FPIs with different cavity length and radius of curvature of the spherical cavity have been made.They are found to be excellent in improving the extinction ratios for more than 30 d B when compared with the FPI with parallel cavity mirrors.2.Based on the fiber FPI tip sensors,the fiber temperature sensors with wide temperature dynamic range over 20??200?have been achieved.The average sensitivity is up to 25 pm/?while the temperature resolution is around 0.8?.In addition,the liquid index sensing was also demonstrated using water-based solutions over the index range of 1.31?1.36.The average sensitivity can be up to 30 d B/RIU with the index sensitivity of 3×10^-3RIU.3.To achieve the high accuracy displacement sensors using cascaded FPIs containing the fiber spherical FPI cavity and an external air FPI when a gold mirror is placed behind the spherical FPI.The best extinction ratio is 40 d B and the displacement sensitivity is 9.0 nm/?m which corresponds to the spatial resolution of 2.2 nm.