Abstract
In this paper we present an all-fiber interferometric sensor for the simultaneous measurement of strain and temperature. It is composed of a specially fabricated twin-core fiber spliced between two pieces of a single-mode fiber. Due to the refractive index difference between the two cores in a twin-core fiber, a differential interference pattern is produced at the sensor output. The phase response of the interferometer to strain and temperature is measured in the 850–1250 nm spectral range, showing zero sensitivity to strain at 1000 nm. Due to the significant difference in sensitivities to both parameters, our interferometer is suitable for two-parameter sensing. The simultaneous response of the interferometer to strain and temperature was studied using the two-wavelength interrogation method and a novel approach based on the spectral fitting of the differential phase response. As the latter technique uses all the gathered spectral information, it is more reliable and yields the results with better accuracy.
Highlights
Fiber-optic interferometers have been widely used for measurement applications [1] because of their small sizes, possibility of remote operation, high measurement precision, and sensitivity
We address the issue of the simultaneous measurement of strain and temperature with the use of an interferometric sensor based on a specially designed twin-core fibers (TCFs)
We studied the performance of the inline interferometric sensor for temperature
Summary
Fiber-optic interferometers have been widely used for measurement applications [1] because of their small sizes, possibility of remote operation, high measurement precision, and sensitivity. A different type of MZI was proposed in [17], employing a double-cladding fiber and two long-period gratings In such a case, the interference fringe and spectral envelope shifts were measured under strain and temperature variations. We have proposed a novel retrieval method based on fitting the simultaneous response to temperature and strain changes with spectral sensitivity curves, measured individually for each parameter. We demonstrate that such an approach significantly improves the resolution of simultaneous measurements compared to the traditional two-wavelength interrogation approach. Another advantage of this technique is in enlarging the free spectral range (FSR) of the sensor and extending the measurement range
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