An assembly and method for a fiber grating package comprising a rod having a first end and a second end and a coefficient of thermal expansion. A first end cap includes a first base having a first opening formed therein to receive the rod for movement of the first end cap along the rod to a first position adjacent to the first end of the rod. The first end cap further includes a first cantilever member extending from the first base and the first cantilever member has a first contact point thereon. A second end cap includes a second base having a second opening formed therein to receive said rod for movement of said second end cap along said rod to a second position adjacent to the second end of the rod. The second end cap further includes a second cantilever member extending from the second base and the second cantilever member has a second contact point thereon. The first end cap and the second end cap have a common rate of thermal expansion that is greater than the coefficient of thermal expansion of the rod. A portion of an optical fiber includes a Bragg grating, the portion of the optical fiber being attached between the first contact point and the second contact point. The portion of an optical fiber has a length defined by the distance between the first and second contact points, such that the length of the portion remains substantially unchanged in an operating range of temperature when the first end cap occupies the first position and the second end cap occupies the second position.