Hybrid Fiber Bragg Grating/Long Period Fiber Grating Sensor for Strain/Temperature Discrimination

A grating sensor system for simultaneously determining strain and temperature is disclosed, which system comprises a light source for providing a continuous broadband light a single mode fiber coupled to the light source a hybrid fiber grating sensor written into the single mode fiber, the sensor comprised of a long period grating having a first center wavelength and first and second fiber Bragg gratings respectively having second and third center wavelengths for respectively reflecting light therefrom at about the second and third center wavelengths, with the first center wavelength being between the second and third center wavelengths, the long period grating producing a broadband power loss around its first center wavelength, the first center wavelength shifting with strain and temperature, the sensor measuring the effect of the long period grating wavelength shift on the relative intensities of the light reflected from around the second and third wavelengths an optical analyzer responsive to the reflected light signals from the hybrid fiber grating sensor for measuring the wavelengths and intensities in the reflected light signals and a circuit responsive to the measured wavelengths and intensities of light from the optical analyzer for simultaneously calculating the strain and temperature being sensed by the sensor.