Sensitivity Of Fiber Bragg Grating Research Articles

Influence of Manufacturing Parameters and Temperature on the Radiation Sensitivity of Fiber Bragg Gratings

For the first time the radiation sensitivity of Bragg gratings was investigated as a function of hydrogen loading pressure before and fiber tension during grating inscription, of the recoating procedure, and of the grating temperature. At -50°C the radiation-induced Bragg wavelength shift was about two times higher than at room temperature. This should be considered when selecting Bragg gratings e.g., for certain space applications.

Effect of the Fiber Coating on the Radiation Sensitivity of Type I FBGs

We have studied the influence of the fiber coating on the radiation sensitivity of fiber Bragg gratings (FBGs). These FBGs are draw tower gratings written before applying the coating in a fiber with a photosensitive 18-mol.% GeO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> -doped core. Using a Co <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">60</sup> source we irradiated polyimide, acrylate, and ormocer coated gratings as well as mechanically stripped ormocer coated FBGs up to a 40-kGy dose. This total dose level corresponds to a near-earth space radiation environment mission. We show that the coating type must be taken into account for correctly interpreting ionizing radiation effects on FBGs.

Influence of Fiber Composition and Grating Fabrication on the Radiation Sensitivity of Fiber Bragg Gratings

The radiation-induced Bragg wavelength shift (BWS) was measured with type I gratings made of 12 fibers with very different composition, i.e. of fibers with an extremely different radiation-induced attenuation. With two of the fibers fabrication parameters like laser intensity, hydrogen loading, and annealing conditions after grating inscription were varied. With another fiber type I and type II gratings were made by a completely different process. With gratings made under identical conditions of the twelve fibers the radiation-induced BWS only varied by about a factor of three. Varying the fabrication parameters led to BWS differences up to nearly a factor of ten.

Resolving cross sensitivity of fiber Bragg gratings with different polymeric coatings

An approach to resolve the cross sensitivity of fiber Bragg gratings (FBGs) is proposed by the adoption of different polymers as the coating materials for gratings. From the different optical responses resulted from the gratings of different polymeric coatings, sensitivity to individual parameter can be exactly revealed. As an application of this approach, simultaneous discrimination of axial strain and temperature with two FBGs of different polymeric coatings is demonstrated with the axial strain and temperature sensitivities of 1.228pm∕με and 11.433pm∕°C for the acrylate-coated FBG, and 1.170pm∕με and 11.333pm∕°C for the polyimide-coated FBG, respectively.

Design and synthesis of a packaging polymer enhancing the sensitivity of fiber grating pressure sensor

A packaging polymer (PP-1) that can enhance the sensitivity of fiber Bragg grating (FBG) pressure sensor was designed and synthesized from hydroxyl terminated polypropylene oxide oligomers, toluene diisocyanate (TDI), 1,4-butandiol as chain extender, catalyzer, foam agent and foam stabilizer. The testing results show that the Young’s modulus, Poisson’s ratio of the packaging polymer are 9.0 × 10 6 N m −2 and 0.49, respectively. The static pressure sensitivity of fiber optical Bragg gratings packaged by PP-1 was discussed. The theoretical pressure sensitivity of FBG packaged with the polymer cylinder is −1.73 × 10 −3 MPa −1, which is 896 times of that of the bare FBG (−1.93 × 10 −6 MPa −1). And its measured pressure sensitivity is −1.10 × 10 −3 MPa −1, which is 558 times of that of the bare FBG.

A study of the temperature sensitivity of fiber Bragg gratings after metallization

In order to embed fiber sensors into metal material, the fiber sensors must be protected.Experiments using electroless plating of a nickel-clad fiber Bragg grating (FBG) have beencarried out four times in order to learn its temperature sensitivity and the relationshipbetween temperature sensitivity and plating thickness. In each experiment, the platingthickness and the corresponding temperature sensitivity were measured, thus achieving thetemperature sensitivities of nickel-clad FBG with different plating thickness. A techniquefor FBG surface electroless plating is proposed. The strains and stresses on thenickel-clad FBG under varied temperature are analysed. The theoretical model of thetemperature sensitivity of nickel-clad FBG is deduced. The relationship betweentemperature sensitivity and plating thickness of nickel-clad FBG is analysed in theoryand verified by experiment. When plating thicknesses are 1.42, 4.26, 15.625 and38.35 µm,the temperature sensitivities of FBG, with a wavelength of 1544.06 nm, are 12.1354, 14.3092, 17.9334and 19.6499 pm °C−1 in theory and the experimental results are 12.09, 13.83, 17.48 and19.605 pm °C−1. The results of theoretical analysis match those from experiments. The hysteresis ofthe wave-shift is discussed with hysteresis disappearing after heat treatment.

Finite Element Analysis of Multi-axis Strain Sensitivities of Bragg Gratings in PM Fibers

This article presents a numerical analysis of the sensitivity of fiber Bragg grating (FBG) sensors written into polarization maintaining fibers to transverse and thermal loading. These sensors are typically applied for the measurement of multiple strain components for the monitoring of civil structures. The finite element analysis includes both the optical and mechanical variations in the optical fiber. Five fiber types typically used in FBG sensors (elliptical core, D-fiber, elliptical core SAP, Bow-Tie, and Panda) are compared. It is shown that when only the fiber geometry is considered while the material parameters are approximately the same, the D-fiber demonstrates the highest sensitivity to transverse loading. In addition, it is shown that reducing the fiber cladding diameter significantly improves the sensitivities of the FBG sensor to transverse loads. All fiber types exhibit approximately the same sensitivity to thermal loading.

Method for enhancing temperature sensitivity of fiber Bragg gratings based on bimetallic sheets

We designed what is believed to be a novel structure based on bimetallic sheets to enhance temperature sensitivity of fiber Bragg gratings. The two ends of bimetallic sheets were fixed by bolts, and a fiber Bragg grating was longitudinally affixed to one of the sheets whose expansion coefficient was larger than that of the other. The theoretical and experimental results show that the temperature sensitivity of the fiber Bragg grating was enhanced dramatically by the structure. For example, the temperature sensitivity reached 0.08014 nm/ degrees C when the bimetallic sheets were made of aluminum and iron, which are more than eight times that of a bare fiber Bragg grating. Moreover, it was experimentally demonstrated that the structure has excellent linearity, reversibility, and stability.

Comparison of the temperature dependence of different types of Bragg gratings

AbstractWe investigate and compare the thermal stability and sensitivity of fiber Bragg gratings (FBGs) obtained from different growth mechanisms, including the well‐known types I, IA, IIA and a new abnormal regime, written in high‐Germanium‐doped optical fiber. The highest stability and sensitivity values are achieved for the type IIA grating. © 2005 Wiley Periodicals, Inc. Microwave Opt Technol Lett 45: 305–307, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20804