Standard optical fiber long-period gratings with reduced temperature sensitivity for strain and refractive-index sensing

2002 ◽  
Author(s):  
V. Bhatia ◽  
D.K. Campbell ◽  
T. D'Alberto ◽  
G.A. Ten Eyck ◽  
D. Sherr ◽  
...  
Keyword(s):  
Refractive Index ◽  
Optical Fiber ◽  
Temperature Sensitivity ◽  
Long Period ◽  
Refractive Index Sensing ◽  
Long Period Gratings ◽  
Reduced Temperature

scholarly journals Sensitivity Characterization of Cascaded Long-Period Gratings Operating near the Phase-Matching Turning Point

Sensors ◽  
2020 ◽  
Vol 20 (21) ◽  
pp. 5978
Author(s):  
Wei Zhou ◽  
Yanli Ran ◽  
Zhijun Yan ◽  
Qizhen Sun ◽  
Chen Liu ◽  
...  
Keyword(s):  
Refractive Index ◽  
Temperature Sensitivity ◽  
Turning Point ◽  
Phase Matching ◽  
Long Period ◽  
Long Period Gratings ◽  
High Measurement ◽  
Surrounding Refractive Index ◽  
Wavelength Resolution ◽  
Quality Factor Q

We characterized a cascaded long-period gratings (LPGs)-based sensor that was operating at the phase-matching turning point (PMTP). The cascaded LPGs constructed an in-fiber Mach–Zehnder interferometer (MZI), which exhibited a series of high-quality-factor (Q) narrow-bandwidth resonance peaks. As the LPG operated at the PMTP, the proposed sensor showed an ultrahigh refractive index (RI) and temperature sensitivity, and high measurement precision. In this study, we took an in-depth look at the effects of grating separation on Q-factor and sensitivity. The results showed that the sensitivity to the surrounding refractive index (SRI) reached 4741.5 nm/RIU at 1.4255 and 2138 nm/RIU, over the range of 1.335–1.373. In addition, the temperature sensitivity was around 4.84 nm/°C. With a 0.02 nm wavelength resolution, the RI and temperature sensing limits were 9.3 × 10−6 RIU and 5.5 × 10−3 °C.

scholarly journals Optical Fiber Interferometers Based on Arc-Induced Long Period Gratings at INESC TEC

Sensors ◽  
2021 ◽  
Vol 21 (21) ◽  
pp. 7400
Author(s):  
Paulo Caldas ◽  
Gaspar Rego
Keyword(s):  
Refractive Index ◽  
Optical Fiber ◽  
Cavity Length ◽  
Fiber Optic ◽  
Fiber Diameter ◽  
Long Period Grating ◽  
Long Period ◽  
Long Period Gratings ◽  
Cladding Mode ◽  
Mode A

In this work, we review the most important achievements of an INESC TEC long-period-grating-based fiber optic Michelson and Mach–Zehnder configuration modal interferometer with coherence addressing and heterodyne interrogation as a sensing structure for measuring environmental refractive index and temperature. The theory for Long Period Grating (LPG) interferometers and coherence addressing and heterodyne interrogation is presented. To increase the sensitivity to external refractive index and temperature, several LPG interferometers parameters are studied, including order of cladding mode, a reduction of the fiber diameter, different type of fiber, cavity length and the antisymmetric nature of cladding modes.

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