We present a multiple parameter integrated fiber sensor that can detect vector bending and ambient temperature simultaneously with a single asymmetric multimode fiber Bragg grating. Multimode Bragg gratings were fabricated in an all-silica core fiber by an infrared femtosecond laser, which showed multiple transmission dips in the transmission spectrum. Bending and ambient temperature fluctuations affect the shapes of multiple transmission dips in different ways. In bending, different dips have different sensitivities. On the other hand, temperature fluctuations tended to influence the dips uniformly across different dips. By analyzing the changing spectrum of dips, one can distinguish the changes induced by bending or temperature fluctuations. Furthermore, the high thermal stability of Bragg gratings inscribed by an infrared femtosecond laser can make this double parameter fiber sensor work in very harsh, high-temperature environments.
"The temperature, and strain responses of FBG-in-SMS are easily separated and measured. Comparing with multi-mode FBG reported previously    , the FBGin-SMS combines the SMS spectral characteristics and the grating spectra, making it stable and readily controlled. It also provides a method to tune and optimize the SMS transmission spectrum for sensing when writing a FBG in the SMS structure by tuning the interference through tuning the refractive index. "
[Show abstract][Hide abstract] ABSTRACT: We propose a compact multi-parameter fibre sensing module based on a fibre Bragg grating (FBG) in single─multi─single mode fibre structure (FBG-in-SMS). We experimentally demonstrated that the FBG-in-SMS can measure temperature and strain simultaneously. In addition, we found that the process of writing FBG in SMS could be an effective technique for tuning and optimizing SMS spectrum for sensing.
"Here, we used this fiber for FBGs fabricating. Refractive index gratings are being widely used in temperature sensors  . So, it is possible to measure temperature gradients inside the gyroscope fiber loop using FBGs array written in this fiber type. "
[Show abstract][Hide abstract] ABSTRACT: The article presents the results of writings of type I and type II fiber Bragg gratings in birefringent optical
fibers with an elliptical stress cladding by a single 20 ns pulse of KrF excimer laser (248 nm).
Experimental results on visualization and thermal annealing of these gratings are presented.
V International Research and Practice Conference, Munich, Germany; 10/2013
[Show abstract][Hide abstract] ABSTRACT: We present a fibre optic sensing system for simultaneous strain and temperature measurement based on a narrow band variable optical reflector. The variable optical reflector comprises a single mode fibre Bragg grating and a fibre mode converter. A 2 µm m−1 strain resolution is achievable over a range of 2000 µm m−1 with a temperature accuracy of 0.3 °C. A strain sensor with a range of 12 000 µm m−1 is also demonstrated. The sensing system shows high strain and temperature sensitivities with very good stability.
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