Simultaneous measurement of temperature and strain using dual long-period fiber gratings with controlled temperature and strain sensitivities

Abstract

Unambiguous simultaneous measurement of strain and temperature based on dual long-period fiber gratings by controlling their thermal and strain sensitivities is proposed and experimentally demonstrated. The difference in the wavelength peak shift and the separation with the variation of strain and temperature allows discrimination between the strain and temperature effects, respectively.

Low-cost high-sensitivity strain and temperature sensing using graded-index multimode fibers

“…Based on the principle of the operation, fiber-optic sensors can be classified into intensity based, spectrally based, and interferometric fiber-optic sensors, all of which may be implemented with very simple structures in the form of optical fibers or fiber Bragg gratings (FBGs). For example, intensity-based fiber-optic sensors employed optical fibers with a certain portion of modified cladding material 1 for chemical and biochemical sensing, while single-mode FBGs 2 and long-period fiber gratings 3 (LPFGs) are commonly used as spectrally based fiber-optic sensors in strain and temperature sensing. Interferometric fiber-optic sensors are of great interest because of their high sensitivities.…”

Ultrashort Long-Period Fiber Grating Sensors Inscribed on a Single Mode Fiber Using CO2 Laser Radiation

“…For temperature sensing, the typical values of sensitivities found in the literature range from around 0.05 to 0.3 nm/ ∘ C. The values are higher when more complex sensing structures were created, like, for example, a dual LPFG system [27]. Also, as mentioned by Nam et al [9], sensitivity increases at high temperature: they measured a sensitivity of 0.054 nm/ ∘ C from room temperature to 200 ∘ C, while from 200 ∘ C to 1000 ∘ C, the value was approximately 0.135 nm/ ∘ C [9].…”

“…These gratings are fabricated with periods ranging from hundreds of micrometers to millimetres, and the majority have lengths of around 25-40 mm; representative typical examples reported in the literature are summarized in Table 1 [6,7,9,[19][20][21][22][23][24][25][26][27][28][29][30][31][32][33][34][35][36]. The two exceptions to this range (and the only ones we found in the literature) are the works of Wang [20] and Nam et al [9].…”

“…In this paper, we present LPFGs written in single mode fibers (Corning SMF-28) using CO 2 laser radiation (10.6 m wavelength) with the remarkable characteristic of having a 2 Journal of Sensors [20] CO 2 laser 2.8 * * * Rao and Zhu [21] CO 2 laser 30 * * Vengsarkar et al [22] KrF laser 25.4 * * Rao et al [23] CO 2 laser 40 2000 Lan et al [24] CO 2 laser 46 * * Oh et al [25] CO 2 laser 42, 47, 50 * * Li et al [26] fs laser 25.2 436 Han et al [27] UV light 20 400 Zhang et al [28] Laser * * [35] CO 2 laser 27 * * Bhatia [6,36] UV 10 280 Nam et al [9] Electric arc 2 500 Duan et al [7] fs laser 34 570 * Engraved in a PCF (Photonic Crystal Fiber). * * Not specified.…”

Liquid Resin Infusion process monitoring with embedded superimposed long period and short period Bragg grating sensor.

“…A lot of techniques have been reported to overcome this problem. One of them consists in the use of two superimposed FBG [10] or only long period gratings (superimposed or not) [11]. In all of those sorts of designs the small differences in sensitivities are a limitation to discriminate strain-temperature effects.…”