INPUT OUTPUT FIBER CONFIGURATION IN A LASER PACKAGE DESIGN/

The mechanical and thermally induced stresses are evaluated for differ ent configurations of the input/output (I/O) fibers in a laser package design. We show that, if the fibers experience bending deformations, the mechanical stresses can be minimized by applying a proper ends off -set and that the thermal stresses can be reduced, if necessary, by th e mechanical prestressing of the fibers. We show also that if the opti cal device can be rotated by a small angle around the transverse axis, this rotation can be effectively used for minimizing the stresses. We found that the smallest fiber span can be achieved by making the end planes of the optical device perpendicular to the package's axis. In t his case the I/O fibers become straight, and should be made short enou gh to avoid buckling under the action of the thermally induced compres sive stresses. We suggest that such a configuration is employed, when the appropriate rotation of the optical device iis possible, the fiber ends can be easily aligned, and the support structures are sufficient ly strong to withstand a relatively high thermally induced force from the compressed fiber. This force can be brought down, if necessary, by application of low expansion materials for the package enclosure (suc h as, sag, Kovar or Invar). Although the results of our analysis enabl e a designer to evaluate the mechanical behavior of the I/O fiber of d ifferent configurations, the final selection of the I/O fiber configur ation can be made only after the allowable stresses and the achievable alignment (in the case of straight fiber) are determined experimental ly.