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A novel design of a polarization filter based on photonic crystal fiber (PCF) is proposed in this paper. With the introduction of a gold-coated air hole, the resonance strength is much stronger in y-polarized direction than in x-polarized direction at some particular wavelengths, which is due to the metal surface plasmon effects. At the wavelength of 1.31 μm, the loss of y-polarized mode is 2138.34 dB/cm while the loss is very low in x polarization. Furthermore, the loss peak can be flexibly adjusted from the wavelength of 1.26 to 1.56 μm by changing the thickness of a gold layer, and the loss in y polarization can be kept above 1200 dB/cm. The significant loss in y polarization makes this PCF a good candidate for developing a polarization filter with high performance. [ABSTRACT FROM AUTHOR]

We propose and demonstrate a multi-channel SPR sensor based on the cascade application of the single-mode and multimode optical fiber. At this article, we studied the relationship between the gold film thickness and the sensing performance of the multimode fiber-based SPR sensor, the larger is the gold film thickness, the longer is the resonance wavelength, and the better is the sensitivity. We also studied the relationship between the grinding angle of the single mode optical fiber and the sensing performance of the single mode fiber-based SPR sensor, the larger is the grinding angle, the longer is the resonance wavelength, and the better is the sensitivity. Based on the above research, the reflected light of the single mode fiber-based SPR sensor is injected into the multimode fiber, and the multi-channel fiber-based SPR sensor is realized by fabricating transmitted SPR sensor on the multimode fiber. We realize the designable dynamic range adjustment by the cascade application of the single-mode and multimode optical fiber, and the sensitivity keeps constant. When the thickness of the gold film on the multimode fiber is 35 nm and the grinding angle of the single mode fiber is 16°(the gold film on the single mode fiber has a fixed thickness of 50 nm), the sensitivity of the two sensing zone on the multi-channel SPR sensor reach 2115 nm/RIU and 5212 nm/RIU respectively. [ABSTRACT FROM AUTHOR]

We propose and demonstrate a reflective-distributed surface plasmon resonance (SPR) sensor based on the twin-core fiber. Firstly, we study the effects of the fiber dual tapered (DT) probe grinding angle on the SPR dynamic range. The results show that for larger grinding angles, the resonance wavelength increases, resulting in a higher testing sensitivity. By using this method, we can make the sensor operate in an optimal waveband. Secondly, on the basis of the results above, we grind the DT probe to be an asymmetric wedge shape to configure two grinding angles (6° and 17°) to realize the distributed sensing. Results show that, with the refractive index detecting a range of 1.333–1.385, we can get two separated sensing zones, 591–715 nm and 729–966 nm, the testing sensitivity are 2385 nm/RIU and 4558 nm/RIU respectively. By using this method, we can detect multiple analytes in the same sensing area simultaneously, besides that we can also effectively compensate for the errors caused by background index interference, and the refractive index change resulting from the non-specific binding, or physical absorption and others. It worth to say that by using this method, we can adjust and control the resonance wavelength by changing the fiber grinding angle, while keeping the testing sensitivity is not reduced. For practical applications, this reflective distributed fiber-based sensor is much suitable for biochemical sensing, it has small size and can enter a small testing spaces (μm scale). The diameter of the twin-core fiber is the only 125 μm, which helps to be integrated into a micro-fluidic chip. In this paper, we integrate the fiber probe into an infusion needle to simulate blood vessels on-line monitoring. [ABSTRACT FROM AUTHOR]