Demountable connection for polymer optical fiber grating sensors

The authors fabricated a demountable Ferrule connector/Physical contact connection between silica fiber and a polymer optical fiber (POF) containing a fiber Bragg grating. The use of a connector for POF grating sensors eliminates the limitations of ultraviolet glued connections and increases the ease with which the devices can be applied to real-world measurement tasks. © 2012 Society of Photo-Optical Instrumentation Engineers (SPIE)

Influence of mounting on the hysteresis of polymer fiber Bragg grating strain sensors

Fiber Bragg grating sensors recorded in poly(methyl methacrylate) fiber often exhibit hysteresis in the response of Bragg wavelength to strain, particularly when exposed to high levels of strain. We show that, when such a fiber grating sensor is bonded directly to a substrate, the hysteresis is reduced by more than 12 times, compared to the case where the sensor is suspended freely between two supports

Strain response of POF sensors

With regard to polymer fibre Bragg gratings, we investigate one of the consequences of the visco-elastic nature of the constituent polymer: hysteresis in the response of wavelength shift vs sensor elongation. We show that when a grating sensor is directly bonded to a substrate, the hysteresis is reduced by a factor of 10 from the case where the sensor is freely suspended between two supports

Wavelength drift of PMMA-based optical fiber bragg grating induced by optical absorption

The transmission loss in polymer optical fiber (POF) is much higher than that in silica fiber. Very strong absorption bands dominate throughout the visible and near infrared. Optical absorption increases the internal temperature of the polymer fiber and reduces the wavelength of any POF Bragg grating (POFBG) inscribed within the fiber. In this letter, we have investigated the wavelength drift of FBGs inscribed in poly(methyl methacrylate)-based fiber under illumination at different wavelengths. The experiments have shown that the characteristic wavelength of such a POFBG starts decreasing after a light source is applied to it. This decrease continues until equilibrium inside the fiber is established, depending on the surrounding humidity, optical power applied, and operation wavelength

An investigation into the wavelength stability of polymer optical fibre Bragg gratings

The inscription of Bragg gratings has been demonstrated in PMMA-based polymer optical fibre. The water affinity of PMMA can introduce significant wavelength change in a polymer optical fibre Bragg grating (POFBG). In polymer optical fibre losses are much higher than with silica fibre. Very strong absorption bands related to higher harmonics of vibrations of the C-H bond dominate throughout the visible and near infrared. Molecular vibration in substances generates heat, which is referred to as the thermal effect of molecular vibration. This means that a large part of the absorption of optical energy in those spectral bands will convert into thermal energy, which eventually drives water content out of the polymer fibre and reduces the wavelength of POFBG. In this work we have investigated the wavelength stability of POFBGs in different circumstances. The experiment has shown that the characteristic wavelength of a POFBG starts decreasing after a light source is applied to it. This decrease continues until equilibrium inside the fibre is established, depending on the initial water content inside the fibre, the surrounding humidity, the optical power applied, and the fibre size. Our investigation has shown that POFBGs operating at around 850 nm show much smaller wavelength reduction than those operating at around 1550 nm in the same fibre; POFBGs with different diameters show different changes; POFBGs powered by a low level light source, or operating in a very dry environment are least affected by this thermal effect