We propose an intensity-modulated surface plasmon resonance (SPR) sensor based on a four-layer Kretschmann structural model. To achieve high-sensitivity intensity detection for the measured sample, a silver/gold (Ag/Au) composite film structure is proposed and optimized by a numerical simulation method, and then the chitosan thin film modified by glutaraldehyde cross-linked as an active layer for adsorbing measured sample is applied and immobilized onto the surface of the Ag/Au composite film by spin-coating technique. In addition, a reference beam is introduced into the system to raise its resolution and stability. Measurements are taken while varying the trace copper(II) ion (Cu2 + ) concentration from 0 to 5 ppm, and the SPR sensor is found to possess sensitivities of 0.9147 and 0.4466 ppm − 1 at Cu2 + concentrations of 0 to 3 and 3 to 5 ppm, respectively. The concentration resolution is 0.015 and 0.030 ppm for the trace Cu2 + concentration of 0 to 3 and 3 to 5 ppm, respectively.
A fiber-optic refractive index sensor assisted surface Plasmon resonance of metal dielectric layer around a longperiod
fiber-optic grating with hollow fiber core has been proposed and comprehensively analyzed. Its operation
principle is based on the efficient energy transfer between the fiber waveguide mode and the co-directional surface
Plasmon waves excited with a long-period fiber-optic grating properly designed by the light refracted through the
interface between the waveguide area and the metal dielectric film. The long-period fiber-optic grating is fabricated on a
waveguide area of a specially designed fiber-optic with hollow fiber core. Simulations have been carried out in coupled
mode theory of fiber-optic gratings in the wavelength ranges from 1500 to 1600nm, and for sensing characteristics of
refractive index. Unlike a previous proposed fiber Bragg grating fabricated on this kind of fiber, t the sensitivity of the
long-period fiber-optic grating SPR refractive index sensor is much higher than that of a FBG in the same structure. The
proposed long-period fiber-optic refractive index sensor assisted surface Plasmon resonance is compact, light weight,
and highly sensitive with a large sensing range
The loss theory of all the factors impacting on the output signal of the EFPI fiber-optic sensor is comprehensively
analyzed. The results indicate that the fringe visibility and the output light intensity reduce after being affected by these
factors, but the influence of other factors except for the F-P cavity length is very small and can therefore be neglected,
and that the larger mode field diameter of the single mode optical fiber has a shorter cavity length room for
design/fabrication.
In this paper, to investigate a method improving high temperature response characteristics, the high temperature sensing
properties of fiber Bragg gratings packaged by the red copper and cuprum and aluminum respectively were studied. The
results indicate that the response characteristics of FBG have very good linearity, and the linearity of FBG packaged by
aluminum is best, but its response time is slower because of lower heat conductivity of packing material, and that higher
thermal expansion coefficient of packaging base material can effectively reduce the nonlinearity of FBG sensor in high
temperature environment. At last, a method improving the temperature sensitivity of FBG sensor and reducing FBG's
nonlinear response versus temperature was presented, and packaging material is selected according to response time
versus temperature change.
The novel FBG temperature sensor eliminating lateral strain cross-sensitivity was present and theoretically analyzed. The
temperature sensor characteristic of the FBG based on the method for eliminating lateral strain was researched from
room temperature to 190°C, and the FBG was pressed by lateral force during rising temperature. The lateral force
resulted in the birefringence of the FBG, and the FBG exited two different reflective spectra meeting with the Bragg
condition. The change spacing of the peak value between two reflective spectra is used to eliminate lateral strain crosssensitivity
to temperature, and amend the temperature sensitivity coefficient and the change temperature value.
KEYWORDS: Fiber Bragg gratings, Optical fibers, Reflectivity, Temperature metrology, Chemical species, Thermal modeling, Control systems, Signal to noise ratio, Ultraviolet radiation, Refractive index
In this paper, the thermal degradation mechanism of ultraviolet-induced fiber Bragg gratings (FBGs) written in silica
fiber doped with germanium has been developed. The thermal degradation up to 840 oC has been repeatedly examined,
and their reflectivity and Bragg wavelength change have been carefully observed. In addition, the temperature
characteristic of the FBG is tested by putting it into a silica tube furnace heated from room temperature to 600 oC. The
experiment results obtained has shown that the FBGs' thermal behavior is similar to a spring's. Therefore, a novel
viewpoint, atomic elastic model applied to explain the thermal degradation mechanism of FBGs, is firstly present. The
work is closely related to the use of FBGs for application in temperature sensor field, and the work is also related to
form mechanism of FBGs.
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