A high coupling efficiency optical design compatible with direct modulated and electroabsorptive lasers

An important aspect of the high performance transmitters used in fiber optic telecommunications is the long distance reach capability of these devices. Of particular importance among many parameters affecting the reach distance, is the transfer efficiency of the light from the laser into the optical fiber. This paper presents a brief theoretical background combining the fiber-coupling fundamentals, classical optics, and diffraction theory. An overview of optical schemes currently in use at TriQuint Optoelectronics, and their limitations will be described. The main focus of the discussion details the design and performance of the confocal lens configuration employed to achieve high coupling efficiency. The design is shown to be capable of reaching between seventy and ninety percent peak efficiency when TriQuint manufactured lasers chips are used. Also, discussed is the method of mounting and aligning lenses using a patented optical sub-assembly (OSA) platform. Stability and long term reliability of the assembly technique has been verified through extensive qualification testing. Results from pre-production runs show a close agreement with the predicted performance.