Tilted fiber Bragg grating sensors

Abstract

Optical fiber gratings have developed into a mature technology with a wide range of applications in various areas, including physical sensing for temperature, strain, acoustic waves and pressure. All of these applications rely on the perturbation of the period or refractive index of a grating inscribed in the fiber core as a transducing mechanism between a quantity to be measured and the optical spectral response of the fiber grating. This paper presents a relatively recent variant of the fiber grating concept, whereby a small tilt of the grating fringes causes coupling of the optical power from the core mode into a multitude of cladding modes, each with its own wavevector and mode field shape. The main consequence of doing so is that the differential response of the modes can then be used to multiply the sensing modalities available for a single fiber grating and also to increase the sensor resolution by taking advantage of the large amount of data available. In particular, the temperature cross-sensitivity and power source fluctuation noise inherent in all fiber grating designs can be completely eliminated by referencing all the spectral measurements to the wavelength and power level of the core mode back-reflection. The mode resonances have a quality factor of 10 5 , and they can be observed in reflection or transmission. A thorough review of experimental and theoretical results will show that tilted fiber Bragg gratings can be used for high resolution refractometry, surface plasmon resonance applications, and multiparameter physical sensing (strain, vibration, curvature, and temperature).

The Influence of Fibre Bending on Polarization-Dependent Twist Sensor Based on Tilted Bragg Grating

“…The wavelength and transmittivity of some dips and peaks of transmitted TFBG spectrum could be influenced by the input light polarization angle and fibre curvature. The wavelength of a specified cladding mode is determined by the grating tilt angle and effective refractive indexes according to the following expressions [19]:…”

“…The reflectivity of individual resonant modes Ri co,cl depends on the modulation of the refractive index according to the following expression [19]:…”

High-sensitive and temperature-self-calibrated tilted fiber grating biological sensing probe

“…Figures 6 and 7 experimentally show that S60 has slightly higher RI than S50, which agrees with fact that S60 contains "young" leukemia cells with a higher intracellular density. An additional feature of the TFBG is temperature self-calibration where spectral shifts due to temperature changes can be eliminated by referencing all wavelengths to the core mode [1], which is unaffected by the surrounding RI and has the same temperature dependence with the other modes, as shown in Figure 7, thereby ensuring that the differential spectra are due solely to RI changes.…”

“…We studied the relationship between the intracellular density of cells (S50 and S60) and their RIs, the experimental results provide a potential way to verify the hypothesis for "density alteration in non-physiological cells (DANCE)". The tilted fiber Bragg gratings (TFBGs) [1,2], due to the induction of a tilted angle between the UV laser beam and the fiber axis (otherwise similar to the normal straight fiber grating), provides an effective way which couples the input light from the forward-propagating core mode to backwardpropagating cladding modes [3][4][5][6]. Because of these cladding excitations, TFBG shows good sensitivity to surrounding refraction index (SRI) change [7][8][9][10][11].…”

EDC-Mediated Oligonucleotide Immobilization on a Long Period Grating Optical Biosensor

“…The most important advantages of this biosensor platform are that it is able to provide biosensing with unique features of label-free, real-time, multiplex, and in-line determination. Various fiber optic biosensors have been presented by employing long period gratings (LPGs) [7,8], tilted fiber gratings (TFGs) [9][10][11] micro fiber Bragg gratings (mFBGs) [12] LPGs in photonic crystal fibers [13] and surface plasmon resonance (SPR) [14].…”