Embedded optical sensor capable of strain and temperature measurement using a single diffraction grating

An embedded optical sensor, comprising:

• an optical waveguide for confining incident light and return light;
• at least one reflective element disposed within said waveguide in the path of said incident light that reflects a portion of said incident light, said reflective element having a first transverse axis and a second transverse axis perpendicular to said first transverse axis, said first and said second transverse axes both being perpendicular to a longitudinal axis;
• a plurality of layers surrounding said reflective element forming a laminated structure;
• each of said layers being oriented in such a way and being comprised of such materials that when laminated together said layers exert forces on said reflective element so as to create unequal transverse stresses in said reflective element;
• said unequal transverse stresses creating birefringence in said reflective element, and said unequal transverse stresses changing with temperature thereby causing said birefringence to change with temperature;
• said birefringence causing a first peak reflection wavelength of said reflective element associated with a first polarization axis of said reflective element and a second peak reflection wavelength of said reflective element associated with a second polarization axis of said reflective element;
• a wavelength spacing being the wavelength difference between said first peak and said second peak and an average wavelength being the wavelength half-way between said first peak and said second peak;
• and
• said wavelength spacing having a sensitivity to temperature and strain which is different from that of said average wavelength, thereby allowing both temperature and strain measurements with said reflective element.