Low cost fiber in the loop (FITL) laser modules

This paper reviews the challenges associated with the design and assembly of low cost, fiber in the loop (FITL) laser modules. The implementation of fiber in the subscriber loop requires low cost, reliable packaging of semiconductor lasers into laser modules. The laser module provides a means of coupling photons from the laser into an optical fiber which requires alignments with stringent micron level tolerances. These alignments must remain stable over the severe loop environment, including temperature conditions from -40°C to +85°C, for the lifetime of the module. The design of the laser module must also satisfy mechanical, thermal, and electrical constraints. All these issues must be addressed while balancing the design between performance and cost, with low cost being the major driver for FITL applications