Wenwen Qian

High-sensitivity temperature sensor based on an alcohol-filled photonic crystal fiber loop mirror.

A compact temperature sensor based on a fiber loop mirror (FLM) combined with an alcohol-filled high-birefringence photonic crystal fiber (PCF) is proposed and experimentally demonstrated. The output of the FLM is an interference spectrum with many resonant dips, of which the wavelengths are quite sensitive to the change of the refractive index of the filled alcohol for the interference of the FLM. Simulation analysis predicts a high temperature sensitivity, and experimental results show it reaches up to 6.6 nm/°C for the 6.1-cm-long PCF used in the FLM.

Photonic Crystal Fiber Strain Sensor Based on Modified Mach–Zehnder Interferometer

In this paper, a novel strain sensor is proposed and demonstrated by employing a modified photonic crystal fiber (PCF)-based Mach-Zehnder interferometer, in which a collapsed region is introduced at the middle point of the PCF to improve the extinction ratio. Experimental results show that this proposed structure has a high sensitivity of 11.22 over a range of 1.28 and high-temperature stability.

Partially liquid-filled hollow-core photonic crystal fiber polarizer

A compact fiber polarizer is demonstrated by the filling of selected air holes of a hollow-core photonic crystal fiber (PCF) with a liquid. The liquid-filling results in an asymmetric waveguide structure, leading to a large polarization dependent loss. A 6 mm long ethanol-filled PCF exhibits a polarization extinction ratio of ∼18 dB over a wavelength range from 1480 nm to 1600 nm.

Temperature Sensing Based on Ethanol-Filled Photonic Crystal Fiber Modal Interferometer

A modal interferometer made of a short ethanol-filled photonic crystal fiber (PCF) combined with a fully collapsed splicing with single-mode fibers (SMFs) is proposed for temperature measurement. Two fully collapsed splicing regions between the ethanol-filled PCF and SMFs excite and recombine two interfering modes in the ethanol-filled PCF. The interference spectrum of the ethanol-filled PCF is more sensitive to temperature than that of original PCF. By monitoring one peak wavelength shift of the ethanol-filled PCF modal interference spectrum, the temperature sensitivity reaches up to -0.35 nm/°C for a 3.25-cm long ethanol-filled PCF.

A high sensitivity refractometer based on a partial liquid-filled hollow-core photonic bandgap fiber

A novel and high sensitivity refractometer is realized by using a short partial liquid-filled hollow-core photonic bandgap fiber (HC-PBGF). Since the liquid filled into partial air-holes of HC-PBGF forms an asymmetric waveguide structure, the confinement loss of the partial filled HC-PBGF is high sensitive to the refractive index of the filled liquid when the wavelength of the input light on Y polarization mode is fixed at the band gap edge. The proposed refractometer can realize a trace measurement by filling the tested liquid into HC-PBGF partially with 1 mm length and the refractive index sensitivity in theory is as high as 1.5×10−8 at approximately 1.333.

Optical fiber sensors based on photonics crystal fiber loop mirrors

We summarize various sensors based on photonic crystal fiber loop mirrors proposed by our research team, including strain sensors, temperature sensors and curvature sensors. Both of highly birefringent and lowly birefringent photonic crystal fibers (PCFs) have been inserted into fiber loop mirrors (FLMs) as the sensing elements. A temperature-insensitive strain sensor with highly birefringent PCF based FLM has been realized and it has a strain sensitivity of 0.23 pm/µe in the range of 0–30 me. For a low-cost, a demodulation is proposed by using a distributed-feedback (DFB) laser as the light source and an optical power meter instead of an expensive OSA. Strain and curvature sensors based on FLMs are also demonstrated by using a lowly birefringent PCF, which has a strain sensitivity of 0.457 pm/µe and a curvature sensitivity of 0.337 nm/ m −1 , respectively. Further, a novel and compact temperature sensor based on a FLM combined with an alcohol-filled highly birefringent PCF is proposed and experimentally demonstrated and it has a high sensitivity as high as 6.6 nm/°C.

Design of Partial Liquid-Filled Hollow-Core Photonic Bandgap Fiber Polarizer

A novel polarizer is designed by liquid filling in partial air-holes of hollow-core photonic band gap fiber (PBGF) forming an asymmetric waveguide structure, which leads to one polarization leaking out while the orthogonal polarization remains propagating along the fiber with a relatively low loss. Applied a full-vector finite-element (FEM) method, a series of polarizer structures with different water-filled regions has been simulated for a better performance on the polarization extinction ratio and the insertion loss. Through optimization, the proposed polarizer has a high polarization extinction ratio more than 32 dB.

Design of partial liquid-filled hollow-core photonic bandgap fiber polarizer

A novel polarizer is designed by liquid filling in the partial air holes of hollow-core photonic bandgap fiber (PBGF) forming an asymmetric waveguide structure. Applied a full-vector finite-element (FEM) method, it is demonstrated that the proposed polarizer has a high polarization extinction ratio more than 35 dB.

The polarization properties analysis on photonic crystal fibers side-pulsed by CO2 laser

We have theoretically investigated the polarization properties of a single-mode photonic crystal fiber (PCF), which is pulsed one-side by CO2 laser resulting in partial air-holes collapse and deformation. The CO2 laser micro-fabrication is a common way in PCF post-processing, which is used widely both in writing fiber gratings on PCFs and making optical components such as PCF polarizers. A series models with different valley depth which is due to the collapsed air-holes have been simulated by using a full-vector finite-element method (FEM) with a perfectly matched layer (PML). The theoretical results show that the deeper valley causes a larger insertion loss, at the same time, leading a larger polarization dependence loss (PDL). This research provides an insight into the side-pulsed PCF as well as a guidance on the experiment of CO2 laser micro-fabrication on PCFs.