| Optical fiber sensors have become an important research topic because of its lightweight,small,immunity to electromagnetic interference and other advantages.Currently,optical fiber sensors have been widely used in the industrial control,environmental monitoring and many other fields.Obviously,research on optical fiber sensors for simultaneous measurements is of great significance,not only it can decrease the number of the sensors,reduce the costs and complexity of the sensing system,but it's also an effective way to solve the problem of cross sensitivity.In this paper,two different kinds of optical fiber sensors for simultaneous measurements are designed and experimentally investigated.The main work and innovations are as follows:(1)The development of optical fiber sensors has been introduced.Introduction and research status of three types of interferential optical fiber sensors and two kinds of fiber grating sensor has been summarized.What's more,research of the optical fiber sensors for simultaneous measurements has been introduced.(2)Based on the principle of MZI,a two-peanut-taper MZI optical fiber sensor for temperature measurement is proposed.The two peanut tapers forming the MZI are fabricated in a standard single-mode optical fiber by fusion-splicing method using the commercial fiber fusion splicer.By using the two-peanut-taper MZI,the measurement for high temperature over 1101.96? can be achieved.At a high temperature of 617.76?-940.3?,the sensitivity of the two-peanut-taper MZI sensor can reach 119 pm/?,and the linearity is over 0.99.This kind of sensor has many advantages such as ease of fabrication,compact size,high sensitivity,etc.(3)A new compact optical fiber sensor for simultaneous measurement of strain and temperature is designed and experimentally investigated after analyzing the principle of the MZI and FBG.The proposed sensor consists of a two-peanut-taper MZI and in-line embedded FBG,the two tapers are fabricated by the fusion-splicing method forming on the two sides of the FBG,respectively.The strain and temperature responses of the sensor are tested,respectively.(4)A partial discharging and tapering method using the fusion splicer to further improve the sensitivities of optical fiber sensor is proposed.By repeating discharging,microfiber taper with different diameter can be formed in the center of the compact sensor based on the two-peanut-taper MZI and embedded FBG.Through tapering the center of the sensor,the diameter of the center of the sensor at a length of 35 mm is changed to 92.25 ?m.And then measurements of strain and temperature using the tapered sensor are carried out.The strain sensitivities of the MZI and FBG change to 1.93 pm/?? and 0.904 pm/??,the temperature sensitivities are 56.6 pm/? and 11.3 pm/?,for MZI and FBG,respectively.Several tapered sensors with different diameter are fabricated and then investigated how this partial discharging and tapering method affects the properties of the sensor.(5)A new optical fiber sensor of simultaneously measuring gas pressure and temperature is presented.The proposed sensor utilizes extrinsic Fabry-Perot interferometer(EFPI)and Michelson interferometer based on a 2×2 3dB coupler as temperature and pressure sensing elements,respectively.The EFPI consists of a standard single-mode optical fiber,a short section of hollow-core optical fiber and coreless optical fiber film.The EFPI probe is fabricated by combining techniques of a femtosecond laser micro-machining and an optimal arc fusion-splicing.The EFPI probe is made in the longer arm of the Michelson interferometer.Static gas pressure and temperature measurements are all investigated,according to the test results,Michelson interferometer can be used for temperature measurement with a temperature sensitivity about 23.68 pm/?,and the EFPI probe can be used for gas pressure measurement with a pressure sensitivity about 4.23 nm/MPa.The gas pressure and temperature variation can be obtained by measuring the resonant wavelength shifts of the MI and FBG simultaneously. |
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