Fiber bragg grating sensor system
First Claim
1. A fiber Bragg grating sensor system comprising:
- a wavelength tunable laser including a wavelength tunable filter for outputting a tunable wavelength light;
a first coupler for receiving the light outputted from the wavelength tunable laser and for splitting the light into two directions;
a reference wavelength generating unit for receiving one of lights split by the first coupler, for generating reference wavelengths to measure real-time wavelengths of the light outputted from the wavelength tunable laser, and for defining one of the reference wavelengths as an absolute reference wavelength;
a fiber Bragg grating array for receiving the other of lights split by the first coupler and for reflecting the lights by each of wavelengths of the grating therein;
a fiber grating wavelength sensing unit for measuring times when each of lights reflected from the fiber Bragg grating array is detected;
a signal processing unit for receiving times of the reference wavelengths generated from the reference wavelength generating unit and times when lights are detected from the fiber grating wavelength sensing unit, for calculating wavelengths in each time period of light outputted from the wavelength tunable laser, and for calculating wavelengths of the lights detected from the fiber grating wavelength sensing unit; and
a laser wavelength control feedback unit for applying AC voltage to the wavelength tunable filter for output wavelength of the wavelength tunable laser to be periodically changed, and for receiving data of the wavelengths in each time period of the wavelength tunable filter from the signal processing unit and for applying DC voltage to the wavelength tunable filter in order that the wavelengths in each time period of the wavelength tunable filter are regularly repeated.
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Abstract
The present invention discloses a fiber Bragg grating sensor system. The system according to the present invention comprises a wavelength tunable laser; a coupler for splitting output light from the wavelength tunable laser into two directions; a reference wavelength generating unit for receiving one directional output light from the coupler and for generating reference wave-lengths and an absolute reference wavelength in order to measure real-time wavelengths of the wavelength tunable laser; a fiber Bragg grating array for receiving the other directional output light from the coupler and for reflecting lights at each of the wave-lengths of the grating therein; a fiber grating wavelength sensing unit for measuring the time when each of the reflected lights from the fiber Bragg grating array is detected; a signal processing unit for figuring wavelength variation information with the use of the measured signals from the reference wavelength generating unit and for obtaining each of wavelengths of the detected lights from the fiber grating wavelength sensing unit; and a laser wavelength control feedback unit for applying AC voltage and DC voltage to the wavelength tunable filter in the wavelength tunable laser. Also, polarization dependency in the sensor system can be removed further installing a depolarizer or a polarization scrambler at the output end of the wavelength tunable laser. By applying the present invention, measurement accuracy of the grating sensor system 20 can be improved due to enhanced wavelength stability and suppression of polarization dependency. Therefore, the fiber Bragg grating sensor system based on the present invention would replace conventional structure/construction diagnosis systems.
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Citations
12 Claims
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1. A fiber Bragg grating sensor system comprising:
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a wavelength tunable laser including a wavelength tunable filter for outputting a tunable wavelength light;
a first coupler for receiving the light outputted from the wavelength tunable laser and for splitting the light into two directions;
a reference wavelength generating unit for receiving one of lights split by the first coupler, for generating reference wavelengths to measure real-time wavelengths of the light outputted from the wavelength tunable laser, and for defining one of the reference wavelengths as an absolute reference wavelength;
a fiber Bragg grating array for receiving the other of lights split by the first coupler and for reflecting the lights by each of wavelengths of the grating therein;
a fiber grating wavelength sensing unit for measuring times when each of lights reflected from the fiber Bragg grating array is detected;
a signal processing unit for receiving times of the reference wavelengths generated from the reference wavelength generating unit and times when lights are detected from the fiber grating wavelength sensing unit, for calculating wavelengths in each time period of light outputted from the wavelength tunable laser, and for calculating wavelengths of the lights detected from the fiber grating wavelength sensing unit; and
a laser wavelength control feedback unit for applying AC voltage to the wavelength tunable filter for output wavelength of the wavelength tunable laser to be periodically changed, and for receiving data of the wavelengths in each time period of the wavelength tunable filter from the signal processing unit and for applying DC voltage to the wavelength tunable filter in order that the wavelengths in each time period of the wavelength tunable filter are regularly repeated. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12)
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Specification