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Study Of New Style Tapered Optical Fiber Liquid Refractive Index Sensor

Posted on:2014-01-10Degree:MasterType:Thesis
Country:ChinaCandidate:Z M GuFull Text:PDF
GTID:2248330395996719Subject:Optics
Abstract/Summary:PDF Full Text Request
The existing liquid refractive index (RI) sensors based on silica fiber have beenwidely investigated because of their higher resolution and sensitivity. However, whenmeasuring the refractive index of liquid, the silica fiber sensors have a bad linearityand higher cost of production. They are limited by of inconvenient using. Comparedwith silica optical fiber sensors, plastic optical fiber sensors have many advantages,such as easy fabrication, low cost and better linearity of measuring. Meanwhile, thereare less plastic optical fiber sensors applied to detect refractive index of liquid, so it isgreat significant to detect index in the area.In this paper, we provide a kind of refractive index sensor utilizing the plasticfiber, based on the characteristics of the outside surrounding environment influencesoptical power of tapered fiber, to achieve the measurement of the refractive index ofliquid. The diameter of unprocessed plastic optical fiber diameter is1mm. In thisexperiment, we use heated platform to fabricate tapered plastic optical fiber sensingprobe, which the length of cone and the diameter of fiber can be effectively controlled.We utilize abrasive paper to polish cladding of sensing area, which have successfullymade the fiber diameter of core with245m and0.97cm. In the experiment, lightpower constrained optical fiber sensing probe varies with the change of refractiveindex of the environment. By measuring the light power which goes through thetapered plastic optical fiber, we can detect external refractive index of liquid.In the experiment, by making a certain volume concentrations of glycerinsolution, the liquid refractive index of solution can be changed from1.347to1.417with0.014as an interval, placing sensing probe into the above-described solution.The light will be modulated before coupling into the optical fiber, and the outputpower at the other end of the fiber can be transformed into voltage signal anddisplayed on the digital oscilloscope. During the progress, the light will be modulatedbefore coupling into the optical fiber, photoelectric detector will detect the output power at the other end of the fiber, and then transformed it into voltage signal. Byobservation of the changes of the voltage,the transmission loss of light will also berecognized in different refractive index of glycerin solution. We utilize origin softwareto fitting curved line between light transmission loss and refractive index of glycerin.Experiment result has shown that the increasing of the RI is linearity with thetransmission loss. And the sensitivity of the sensor made by fabricated can be reachedto30.83dB/RIU.We explore the influence to measure refractive index of liquid using differentcore diameter of sensing head, are460m,340m and245m.The experimentalresults show that with the diameter of sensing probe decrease, the sensitivity ofmeasure of refractive index of external liquid will increase.In this paper, we also consider that when temperature on the externalenvironment has changed the influence to measured result of tapered plastic opticalfiber sensor. We first heated the temperature of water from20℃to70℃, the range oftransmission loss of light is from0.038dB to0.097dB. The loss of unit temperatureis0.0018dB/℃. It is thus obvious that temperature of liquid has little influence. Thetapered plastic optical fiber sensor is immune from temperature of external liquid.
Keywords/Search Tags:Plastic optical fiber, Taper, Refractive index of liquid, Sensor
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