We present a Fabry-Perot interferometer for microfluidic flow rate sensing. The FPI was composed by a pair of fiber Bragg grating reflectors and a micro Co<sup>2+</sup>-doped optical fiber cavity, acting as a “hot-wire” sensor. A microfluidic channel made from commercial silica capillary was integrated with the FPIs on a chip to realize flow-rate sensing system. By utilizing a tunable pump laser with wavelength of 1480 nm, the proposed flowmeter was experimentally demonstrated. The flow rate of the liquid sample is determined by the induced resonance wavelength shift of the FPI. The effect of the pump power on the performance of our flowmeter was investigated. The dynamic response was also measured under different flow-rate conditions. The experimental results achieve a sensitivity of 70 pm/(μL/s), a dynamic range up to 1.1 μL/s and response time in the level of seconds. Such good performance renders the sensor a promising supplementary component in microfluidic biochemical sensing system.
In this paper, a dual-parameter measurement scheme based on an etched thin core fiber modal interferometer (TCMI) cascaded with a fiber Bragg grating (FBG) is proposed and experimentally demonstrated for simultaneous measurement of magnetic field and temperature. The magnetic fluid cladding surrounding the TCFMI was used as a magnetic field-to-refractive index transducer. To depress the temperature influence on the performance of such sensors, an FBG was inscribed in the leading SMF of the TCFMI. Experimental results show that, the reflection of the FBG has a magnetic field intensity and temperature sensitivities of -0.017 dB/Oe and 0.133 dB/℃, respectively, while the Bragg wavelength of the FBG only has a temperature sensitivity of 13.23 pm/℃. By monitoring the reflection wavelength and intensity of the Bragg mode, the intensity of the magnetic field and the temperature variance can be measured, which enables magnetic field sensing under strict temperature environments. Meanwhile the reflective sensing probe is more compact and practical for applications in hard-to-reach conditions.