A novel lensed fiber for high-efficiency coupling between an single-mode fiber (SMF) and a high-power laser diode (LD) with large astigmatism of 176 µm is proposed and demonstrated. We experimentally confirmed that the proposed lensed fiber had a minimum coupling loss of 2.5 dB including a reflection loss of 0.3 dB at both ends of the fiber. In addition the new configuration had a long working distance of 67 µm. We also investigated the tolerance characteristics for various displacements.
Hidehiko Yoda, Taketo Endo, and Kazuo Shiraishi, "Cascaded GI-Fiber Chips With a Wedge-Shaped End for the Coupling Between an SMF and a High-Power LD With Large Astigmatism," J. Lightwave Technol. 20, 1545- (2002)