A lensed GIO fiber with a long working distance for the coupling between laser diodes with elliptical fields and single-mode fibers

The experimental performance of a new lensed fiber employing a graded-index oval-core fiber is presented for the first time. The new scheme has a long working distance and a high coupling efficiency compared with conventional wedge-shaped lensed fibers. Experiments show that the coupling loss between a laser diode, operating at a wavelength of 980 nm with a field profile aspect ratio of 5.9, and single-mode fiber is as low as 1.3 dB with the long working distance of 30 μm. Measured tolerance characteristics against lateral displacement and tilt are acceptable for practical active alignment.