Chunran Sun

Fiber Ring Cavity Laser Based on Modal Interference for Curvature Sensing

Fiber ring laser sensor for curvature measurement based on a single-mode-no-core-single-mode structure is proposed and experimentally demonstrated. Compared with the conventional curvature system, the proposed laser sensor system has a high optical signal-to-noise ratio and a narrow 3-dB bandwidth, which enables the system to monitor the variation of micro-bending more distinctly. In the experiment, changes in peak wavelength show a blue shift when the curvature varies from 0.1225 to 0.4062 m-1. The sensitivity of the curvature is about -22.33 nm/m-1 in the range of 0.2121-0.3463 m-1. The response to the temperature of the fiber laser sensor is also discussed, where temperature sensitivity of 9.23 pm/°C within the range from 10 °C to 100 °C is obtained.

An Optical Liquid-Level Sensor Based on D-Shape Fiber Modal Interferometer

A novel coreless-D-shape-coreless (CDC) fiber structure for liquid-level sensing is proposed and experimentally investigated. The D-shape fiber with cladding partially etched is sensitive to the ambient refractive index change and the CDC structure transmission dip wavelength shifts related to the length of D-shape fiber immersed in the liquid, so liquid level is measured by monitoring the dip wavelength. The sensitivities for three different liquids with the RIs of 1.333, 1.355, and 1.377 are 191.89, 208.11, and 213.80 pm/mm, respectively. The temperature influence is also studied. The sensor exhibits a low-temperature cross-sensitivity of −0.128 mm/°C. The proposed modal interferometer based on the D-shape fiber with high sensitivity, low cost, and easy fabrication is suitable to liquid-level sensing applications.

Solc-Like Tunable Birefringent Fiber Filter Based on Elliptical-Core Spun Fiber

A novel tunable all-fiber birefringent filter based on elliptical-core spun fiber (ECSF) is presented. It is the first time to build a discrete model of spun fiber by using Jones matrix analysis. The transmission characteristics of proposed filter are studied and discussed in detail, while a generalized formulation to express the transmissivity of the birefringent filter is derived. On this basis, the effect factors of filter characteristic are deeply analyzed and simulated. Compared with the conventional fiber-optic Solc filter, the proposal is easy fabricated and implemented with low loss. By utilizing appropriate length and parameters of the ECSF, a narrowband and high-extinction ratio periodic optical filter is realized. The proposed filter also can be finely tuned covering one free spectral range, which has potential applications for fiber sensing and flexible multi-wavelength fiber laser.

Experimental and theoretical study of the in- fiber twist sensor based on quasi-fan Solc structure filter

In this paper, a novel quasi-fan Solc structure filter based on elliptical-core spun fiber for twist sensing has been experimentally investigated and theoretically analyzed. The discrete model of spun fiber has been built to analyze the transmission characteristics of proposed sensor. Both experimental and simulated results indicate that the extinction ratio of the comb spectrum based on quasi-fan Solc birefringent fiber filter varies with twist angle and agrees well with each other. Based on the intensity modulation, the proposed twist sensor exhibits a high sensitivity of 0.02219 dB/(°/m). Moreover, thanks to the invariability of the fiber birefringence and the state of polarization of the input light, the proposed twist sensor has a very low temperature and strain sensitivity, which can avoid the cross-sensitivity problem existing in most twist sensors.