Patent ID: 6295399
Filing Date: 2001-09-25
Classification: G02B

Abstract:
A non-linear 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 and being symmetrical about a line bisecting and orthogonal to the fiber grating, the device comprising:a first expansion member formed of a material having a first coefficient of thermal expansion and extending parallel to the longitudinal axis of the fiber grating and having a length between first and second ends shorter than the fiber grating;a second expansion member formed of a material having a second coefficient of thermal expansion and extending parallel to the longitudinal axis of the fiber grating and having a length between first and second ends at least as long as the fiber grating, said second coefficient of thermal expansion being different from said first coefficient of thermal expansion;a first lever formed unitarily with said second expansion member and having first and second ends and an intermediate portion, said first lever being flexibly connected to a first end of said second expansion member proximate the intermediate portion of said first lever, said first lever being bifurcated at a first end into a pair of prongs, with each of said prongs being formed with a channel at its distal end facing the channel of the other prong;a first connecting arm formed unitarily with said first lever and having first and second ends, said first connecting arm being flexibly joined at its first end to the second end of said first lever and being rigidly connected at its second end to the first end of said first expansion member;a second lever formed unitarily with said second expansion member and having first and second ends and an intermediate portion, said second lever being flexibly connected to a second end of said second expansion member proximate the intermediate portion of said second lever, said second lever being bifurcated at a first end into a pair of prongs, with each of said prongs being formed with a channel at its distal end facing the channel of the other prong;a second connecting arm formed unitarily with said second lever and having first and second ends, said second connecting arm being flexibly joined at its first end to the second end of said second lever and being rigidly connected at its second end to the second end of said second expansion member; anda pair of quartz blocks each elongated along the longitudinal axis of the fiber and secured to a respective end of said fiber grating and each disposed in a pair of said channels in a respective lever prong pair;wherein a first of said pair of prongs of each of said levers is positioned outwardly of the fiber grating and the second of said pair of prongs of each of said levers extends substantially parallel to the longitudinal axis of the fiber toward the other of said levers to leave a gap between the distal ends of the pair of second prongs which is centered at the line bisecting and orthogonal to the fiber grating;wherein said expansion members, said levers, said connecting arms, said quartz blocks and said fiber all lie substantially in a single plane;whereby a change in temperature of said device causes said first and second expansion members to expand and contract differentially, thereby pivoting said first and second levers and, along with the expansion and contraction of said pair of quartz blocks, varying the axial strain in the fiber grating.