Temperature compensating device for fiber gratings

A temperature compensating device for a pre-strained fiber grating of an optical fiber, said temperature compensating device extending along a longitudinal axis of the fiber grating, comprising:

• a first expansion member formed of a material having a first coefficient of thermal expansion and disposed radially outwardly from the longitudinal axis of the fiber grating and having a length at least as long as the fiber grating,
• a second expansion member formed of a material having a second coefficient of thermal expansion and disposed outwardly from said first expansion member and having a length at least as long as the fiber grating, said second coefficient of thermal expansion being different from said first coefficient of thermal expansion;
• a base member affixing a distal end of said second expansion member and said first expansion member to a distal end of the fiber grating;
• and
• a lever having an inner end, an intermediate portion, and an outer end, said lever being flexibly connected to a proximal end of said second expansion member proximate the outer end of said lever and to a proximal end of said first expansion member proximate the intermediate portion of said lever and to a proximal end of the fiber grating proximate the inner end of said lever such that a change in temperature in said device causes said first and second expansion members to expand and contract differentially thereby pivoting said lever to vary the axial strain in the fiber grating so as to maintain a grating wavelength of the fiber grating substantially constant throughout a desired temperature range.