We demonstrate an acid-based sensor from the biofuncationalized microfiber Bragg grating. By electrostatic selfassembly layer-by-layer technique, the film consisting of sodium alginate which has hygroscopic response to the potential of hydrogen is coated on the fiber surface. Consequently, the refractive index variation of the sensing film caused by water absorption can be measured by mFBG’s higher order mode peak which can be translated into pH value information. The sensitivity of the sensor is received as high as 265pm/pH.
We demonstrate a highly-sensitive current sensor by packaging a single taper-based modal interferometer into a copper
tube that is filled with alcohol and surrounded with chrome-nickel wire. As the flowing current in the chrome-nickel wire
is changed, the interference spectrum varies accordingly with sensitivity as high as 1014.5 nm/A2 . Our results are
promising for the current sensing and the electric-tunable filtering.
We demonstrate a temperature-independent displacement sensor by inscribing a periodic grating in a microfiber taper with assistance of the 193-nm ultraviolet exposure technique. The obtained bandwidth is as large as 29.64nm for the grating with diameter of 3.8~6.38μm and length of 6.2mm, respectively. When the displacement is increased from 0 to 1.08mm, the reflecting bandwidth reduces to 3.38nm gradually, producing an average sensitivity of around −22.8nm/mm. The minimum displacement of measurement is ~4.39×10−4mm considering the wavelength resolution of 10pm in the optical spectrum analyzer. Moreover, the temperature-cross sensitivity is suppressed.
A compact microfiber sensor is implemented with the twist of a continuous rectangular microfiber. The structure can exhibit extremely-high sensitivity of around 24,373nm per refractive-index unit and temperature stability of better than 0.005nm/oC, implying a great suppression of cross-sensitivity. Thia sensor is featured with compact size, high sensitivity, easy fabrication, robustness, and low connection loss with all-fiber system.