Chunhua Tan

Three Channel-Spacing Switchable Multiwavelength Fiber Laser With Two Segments of Polarization-Maintaining Fiber

A three channel-spacing tunable multiwavelength fiber ring laser by using two segments of polarization-maintaining fiber (PMF) is experimentally demonstrated. By adjusting the polarization controllers, the wavelength spacing could be efficiently switched among 0.48, 0.73, and 1.45 nm. Moreover, we also analyzed theoretically the equivalent Lyot birefringence fiber filter with two segments of PMF. Theoretical prediction was verified by experimentally obtained multiwavelength outputs.

Simultaneous Measurement of Refractive Index and Temperature Based on Modal Interference

A simple optical fiber sensor configuration for simultaneous measurement of refractive index (RI) and temperature based on modal interference is proposed and experimentally demonstrated. The sensing configuration is formed by splicing two multimode fibers among three single mode fibers. Due to the different sensitivity responses of the two wavelength transmission dips formed by the cladding modes interfering with the core mode, it is possible to measure the RI and temperature by monitoring the wavelength shifts of the two transmission dips. The experimental results indicate that the sensing sensitivities of RI and temperature are -37.9322 nm/RIU and 0.0522 nm/°C within the RI range from 1.3105 to 1.3517 and the temperature range from 25°C to 85°C, respectively. The proposed sensor configuration features the advantages of easy to fabricate, robust, cost effective, and high sensitivity, making it exhibit potential applications in physical, biological, and chemical sensing.

Simultaneous measurement of temperature and strain by combining a fiber Bragg grating and the pigtail fiber covered with epoxy resin

A fiber sensor for simultaneous measurement of temperature and strain based on a fiber Bragg grating (FBG) with the pigtail fiber covered with epoxy resin is presented. The side mode suppression ratio of the FBG will vary with the temperature due to the Fresnel reflection from the interface between the pigtail fiber and the epoxy resin whose refractive index is sensitive to the temperature. The sensor is also capable of simultaneous measurement temperature and strain by combining the Bragg wavelength shift characteristics as the temperature and strain of the FBG.

A novel titration method based on fiber-optic refractive index sensing for the determination of deacetylation degree of chitosans

We describe a novel method for determining the degree of deacetylation (DD) of chitosans from fiber-optic measurements of refractive index. Theory analyses and the experimental setup of the method are introduced and discussed. The analytical performance of the method is described for the determination of alkaline titration end-points. Experimental results reveal that the equivalence point can be directly identified from the titration curve. The proposed method is simple, low-cost, accurate, reliable, and easy to operate for industrial application. The DD values of four chitosan samples obtained with this new method show good agreement with those yielded from 1H NMR. Such a mechanism of refractive-index monitor should open up a new application in the field of chitosanolytic enzymes, such as chitosanase, pectinase that are important in bioprocesses.