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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.