Patent ID: 7515781

Claim:
An optical sensor having a temperature T 1 placed in a medium having a temperature T 2 different from T 1 ,the optical sensor comprising: a) an optical fiber, b) a fiber grating within said optical fiber, c) a first element having a first coefficient of thermal expansion whose properties are altered by the medium, called the altered element, wherein said properties which are altered are material loss, material gain, chemical, thermal, and/or metallurgical, d) a second element having a second coefficient of thermal expansion different from said first coefficient of thermal expansion, called the unaltered element whose said properties are unaltered by the medium and fixed to said first element, and e) at least one strain-tuning element that is fixed to said second element and to said optical fiber wherein said optical fiber is not in contact with said first and second elements and wherein said strain-tuning element compensates for the difference between the thermal expansion coefficients of said first and second elements so that said optical fiber is under a tensile strain due to a difference in temperature between T 1 and T 2 so that the tensile strain of said optical fiber decreases as said first element is altered thereby causing reflected light from the optical fiber to change its wavelength.