Chongke Ji

Multiplex and simultaneous measurement of displacement and temperature using tapered fiber and fiber Bragg grating

A simple method to work out the multiplexing of tapered fiber based sensors is proposed and demonstrated. By cascading a tapered fiber with a fiber Bragg grating (FBG), the sensor head is provided with a wavelength identification, different FBGs provide the sensor heads with different reflective peaks and they can be distinguished in optical spectrum. By compositing several such sensor heads with a multi-channel beam splitter, a star-style topological structure sensor for multipoint sensing is achieved. At the same time, the output intensity at the peak wavelength is sensitive to one external physical parameter applied on the related FBG-cascaded tapered fiber and the central wavelength of the peak is only sensitive to temperature, so that that parameter and temperature can be measured simultaneously. A sensor for dual-point measurement of the displacement and temperature simultaneously is experimentally demonstrated by using a 2 × 2 coupler in this paper. Experiment results show that the sensor works well and the largest sensitivities reach to 0.11 dB/μm for displacement in the range of 0-400 μm, and ∼0.0097 nm/°C for temperature between 20 °C and 70 °C.

A Intensity-Modulated Micro-Displacement Sensor Based on a Tapered Fiber Cascaded with a Fiber Bragg Grating

A intensity-modulated micro-displacement sensor with the high sensitivity based on a tapered fiber cascaded with a fiber Bragg grating (FBG) is proposed and experimentally demonstrated. The sensor head is obtained by cascading a tapered fiber with a FBG, the light reflected by the FBG propagate through the tapered fiber and the intensity of it is affected by the bend degree of the tapered fiber which is caused by displacement. The experimental results show that the sensitivity 5.1131nW/μm is achieved within the measurement range of 0μm to 42μm.

Theoretical studies on a temperature sensor based on an alcohol-filled photonic crystal fiber-long period grating

In this letter, a simple but novel temperature sensor based on an alcohol-filled photonic crystal fiber-long period grating (PCF-LPG) is proposed and studied theoretically. For the sensing principle, a section of alcohol-filled PCF-LPG works as a sensor head. As temperature changes, effective indices of the core mode and the cladding mode change obviously because of the high temperature sensitivity of the filled alcohol so that the difference of effective indices of the core mode and the cladding mode is highly affected by temperature. Therefore, the resonant wavelength which arises from light coupling from the fundamental mode to the forward-propagating cladding modes is very sensitive to temperature due to the mode couplings. By monitoring the output resonant wavelength, we can realize the detection of temperature change. Simulation analysis predicts the sensor has high temperature sensitivity, which reaches up to 8.5 nm/°C as the period of the grating is 650 μm.