GAS FLOW MEASURING APPARATUS USING HEAT COIL TYPE FIBER BRAGG GRATING SENSOR

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The present invention relates to a gas flow measuring apparatus using a hot-wire type FBG sensor for measuring the flow rate of gas by configuring a feedback fiber laser applied with a Sagnac loop filter as using thermo-optic effects, and the apparatus according to an embodiment of the present invention comprises : a sensor unit for generating resistance heat by applying currents to a hot-wire according as the hot-wire having a coil shape is formed in the outer periphery of a fiber bragg grating; a Sagnac loop filter for providing a wavelength for resonance with a reflection spectrum of the fiber bragg grating; a rare-earth doped fiber for providing a gain for resonant oscillation by being connected to an output terminal of the Sagnac loop filter; a pumping laser diode for activating the rare-earth doped fiber; and a wavelength division multiplexer for configuring a feedback laser by connecting the sensor unit, the rare-earth doped fiber, and the pumping laser diode. The present invention according to the embodiment accurately measures gas flow variation at low costs through a simple structure, and ensures a stable output center wavelength through durability improvement.