Turn-Around Point Long-Period Fiber Grating Fabricated by CO₂ Laser for Refractive Index Sensing


Turn-around point long period fiber gratings (TAP-LPFG) are designed by simulations and fabricated by CO2 laser point-to-point irradiations. It is found that the transmission power of a TAP-LPFG exhibits a large linear range with high sensitivity in response to the surrounding refractive index change. The linear power-refractive index relation enables an intensity based refractive index sensor with significantly simplified calibration and instrumentation. By choosing the grating period, the TAP-LPFG can be designed to operate in different refractive index ranges. The TAP-LPFG sensors are demonstrated for detection of sucrose solutions, refractive index matching liquids and low concentration glucose solutions. Compared with the traditional wavelength-shift based measurement method, intensity based TAP-LPFG sensors may provide a cost effective solution for fast and in situ detection of refractive index changes.


Electrical and Computer Engineering


United States. Department of Energy
National Science Foundation (U.S.)


The research is supported by the U.S. Department of Energy through the University Coal Research Program (DE-NT0008062) and the National Science Foundation (CMMI-1235202).

Keywords and Phrases

Cost-effective solutions; Glucose solution; Grating periods; High sensitivity; Intensity-based; Linear range; Long period fiber grating; Low concentrations; Measurement methods; Optical fiber sensor; Refractive index changes; Refractive index matching; Refractive index sensing; Refractive index sensor; Sucrose solution; Surrounding refractive indices (SRI); Transmission power; Turn-arounds, Carbon dioxide; Glucose; Glucose sensors; Lasers; Refractometers; Semiconductor quantum wells; Sensors; Sugar (sucrose), Refractive index; Intensity based measurement; Turn-around point long period fiber gratings

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Article - Journal

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© 2013 Elsevier, All rights reserved.

Publication Date

01 Feb 2013