Concatenation of surface plasmon resonance sensors in a single optical fiber using tilted fiber Bragg gratings

Abstract

An inline multichannel surface plasmon resonance (SPR) sensor scheme excited with tilted fiber Bragg gratings (TFBG) in a chromium- and gold-coated fiber is demonstrated. The channels have different operating wavelengths, different TFBG tilt angles, and hence different refractive index operating ranges. The polarization state of each channel based on the TFBG orientation can be used to switch each SPR sensor on or off as required. This system provides an operating range of 1.40-1.44 RIU and a sensitivity of around 500 nm/RIU. The multiplexing in a single optical fiber of a number of TFBG-SPR sensors is demonstrated for the first time.

Ultrasensitive plasmonic sensing in air using optical fibre spectral combs

“…11) for wavelengths at which light has been coupled out of the core. When a metal film is deposited on the cladding surface, the cladding modes that are phase-matched to the SPP tunnel energy into it and the spectrum is modified121314. In the TFBG spectrum, the Bragg resonance is insensitive (in wavelength and power) to the surrounding refractive index changes.…”

Distributed fiber surface plasmon resonance sensor based on the incident angle adjusting method

“…Subsequently, distributed optical fiber SPR sensors based on polymerized film have been presented [10,11], but the additional layer reduces the energy of the surface wave interacting with the targeted medium, thus leading to a decrease in the sensitivity. Recently, people have employed fiber Bragg gratings in chromium-and gold-coated fibers to realize the distributed sense, which provides different refractive index operating ranges, but the sensor sensitivity is relatively low [12,13].To summarize, the main factors that affect the resonance wavelength (dynamic range) include the incident angle, metal type, metal film thickness, substrate (prism or fiber core) refractive index, modulated layer refractive index, and thickness, among other factors. For the incident angle factor, normally, it is not feasible to change the incident angle in a fiber structure [8,14,15].…”

“…Subsequently, distributed optical fiber SPR sensors based on polymerized film have been presented [10,11], but the additional layer reduces the energy of the surface wave interacting with the targeted medium, thus leading to a decrease in the sensitivity. Recently, people have employed fiber Bragg gratings in chromium-and gold-coated fibers to realize the distributed sense, which provides different refractive index operating ranges, but the sensor sensitivity is relatively low [12,13].…”

“…For the substrate index factor, it is hard to change the refractive index of the substrate [16,17]. For the modulated layer factor, the coverage of the modulated layer needed to move the dynamic range is at the expense of the sensitivity of the sensor [10][11][12][13].…”

“…Third, the eccentriccore structure integrates dual sensing zones in the same fiber, which helps to maintain the stability and integrity of the sensor. Fourth, the two sensing zones employ the same sensing scheme, which avoids the testing sensitivity reduction because of the cascade scheme based on the sensing film modification [10][11][12][13].…”