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A magnetic field sensor based on a tilted fiber Bragg grating (TFBG) coated with magnetic fluid is proposed and demonstrated experimentally. The sensing element is made by injecting the magnetic fluid into a capillary tube which contains a TFBG. The resonant wavelengths of the cladding modes of TFBG shift by varying the magnetic field which is perpendicular to the axis of TFBG. The results indicate that the resonant wavelength shifts of the cladding modes show a nonlinear dependence on the magnetic field. As the magnetic field increases to 32 mT, the largest resonant wavelength shift reaches to 106 pm. Moreover, this sensor shows good repeatability when it is used for magnetic field sensing.

We present a method for visual and dynamical measurement of the Rayleigh-Benard convection by using fiber-based digital holographic interferometry. A SM600 fiber with 4 μm core diameter is used instead of conventional pinhole, which has better performance to filter out the noises, effectively modify the structure of the optical path and relax the requirement of the laser performance (e.g., coherence length and beam uniformity). The experimental results show the development process of Rayleigh-Benard cell in the container. The corresponding Rayleigh number is 3.6. In the process, the temperature at the top and bottom plates is controlled at 295 K and 300 K, respectively. The measured temperature distribution and the number of Rayleigh-Benard cell are verified by using simulation and are in good agreement.