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Highlights • The proposed PCF filter can realize three kinds of filtering effects. • Two ultra-large air holes makes the process of plating gold film more convenient. • Ultra-high crosstalks and losses can be obtained at the communication windows. • The filtering bandwidth can reach 700 nm at the communication window of 1550 nm. Abstract In this study, we present a single-polarization photonic crystal fiber filter. The metallic gold is used as the surface plasmon resonance activity material, which is deposited on the inner wall of the two ultra-large holes. The properties of the photonic crystal fiber filter are investigated by the finite element method. By adjusting the structural parameters and gold film thickness, three kinds of filtering effects can be obtained at the communication windows. When the length of the optical fiber is 1 mm, one of the filtering effects can achieve loss of 588.900 dB/cm at the communication window of 1310 nm, and the corresponding filtering bandwidth equals to 270 nm; the other two kinds of filtering effects can be applied to the communication window of 1550 nm, and the losses are 569.682 and 971.330 dB/cm and the corresponding filtering bandwidths equal to 700 and 630 nm, respectively. The proposed photonic crystal fiber filter shows great advantages compared with some previous reports on filtering. [ABSTRACT FROM AUTHOR]

Abstract We propose and investigate a temperature sensor based on Sagnac interferometer with liquid crystal (LC) photonic crystal fiber (PCF) by finite element method (FEM). LC E7 which is anisotropic under electrical field is designed to be infiltrated into the cladding air holes of PCF. The birefringent PCF is then launched into a Sagnac interferometer. The interference spectrum of the Sagnac interferometer is influenced by the thermal effect of LC E7 and thus could be used to measure the temperature. The simulation results show that the temperature measuring sensitivity and resolution reach to 15 nm/K and 6.7E−4 K in the range of 290–320 K. The measuring range and sensitivity could be modified further by optimizing the PCF structure parameters. [ABSTRACT FROM AUTHOR]

A temperature sensor based on modes coupling effect in a liquid crystal-filled microstructured optical fiber was proposed and studied in this paper. The sensing characteristics were investigated by using a full-vectorial finite-element method (FEM) with perfectly matched layer and scattering boundary condition. For the purpose of temperature sensing, liquid crystal E7 was designed to be infiltrated into one cladding air hole in PCF to form a defect core. As the phase matching condition is satisfied, the core modes couple to several different ordered defect core modes, and finally experience a large increase in the confinement loss spectra. Furthermore, the loss spectra shift toward opposite directions in the two temperature segments (15–29 °C, 29–50 °C) for X-polarized (X-pol) direction, while it experiences a blue shift in the temperature range of 15–50 °C for Y-polarized (Y-pol) direction. Numerical simulation results show that the sensitivity reaches −5.26 nm/°C at 30 °C. The coupling effect between the core fundamental mode and high-order defect core modes utilized in this paper will be beneficial to the high-sensitivity detection. [ABSTRACT FROM AUTHOR]

A dual-polarized microstructure fiber sensor is based on surface plasmon resonance, which is arranged of pentagonal lattice to achieve refractive index sensing in the near-infrared spectrum. The gold nanowire-filled fiber sensor exhibits excellent sensing characteristics and improved transmission properties. Finite element method is used for computational analysis and structural optimization for the fiber sensor. When the refractive index of the analyte range from 1.32 to 1.38, dual-polarizd sensing can be implemented as a self-calibration with wavelengths increasing from 700 to 1200 nm. For the proposed sensor, the highest wavelength sensitivity of 10,286 nm/RIU is exhibited with a sensor resolution of 9.72×10−6 RIU, and the corresponding amplitude sensitivity and figure of merit are as high as 544.0 RIU−1 and 146.9. Moreover, the sensing length of at least 1.14 mm ensures accurate detection of optical signals for proposed sensor. Owing to the above advantages, the proposed sensor is suitable for high integration and high precision sensitivity detection. [ABSTRACT FROM AUTHOR]

We propose a Sagnac interferometer (SI) based on ethanol-filled photonic crystal fiber (PCF) with two ultra-large holes for temperature measurement. The phase birefringence of the fully-filled PCF varies significantly with the temperature which is realized by infiltrating ethanol into air-holes. Two ultra-large holes in y direction near the core result in a high birefringence of PCF. By selecting a fiber length of 2.5 cm, the average sensitivity of temperature can be up to -34 nm/°C with a resolution of 0.00029 °C in the wavelength range of 780 nm–2170 nm within temperature variation of 40 °C. The proposed PCF with the simple structure is easy to prepare in the experiment. Furthermore, due to the ultrahigh-sensitivity, the proposed sensor provides a new implementation for accurately temperature measurement. [ABSTRACT FROM AUTHOR]