(6+1) ×1 Fiber Combiner based on Thermally Expanded Core Technique for High Power Amplifiers

摘要

A high-efficiency pump-signal combiner for high power fiber amplifiers based on thermally expanded core (TEC) technique is reported in this paper. TEC technique is used to fabricate mode-field adapter which allows optimization of signal fibers in a monolithic (6+1) ×1 fiber combiner. The combiner is fabricated by connecting a tapered fiber bundle (TFB) to a passive 25/250 (NA=0.06/0.46) double-clad fiber (DCF). By this method, the coupling efficiency of SMF-28 signal fiber at 1064nm improves from 54% to 92.7%. The average pump coupling efficiencies of six 105/125 (NA=0.15) fibers are measured to be 96.7% at 976nm. Furthermore, the average signal transmission efficiency is around 93.3%. The fabricated fiber combiner is spliced to an Yb-doped DCF for use as an all-fiber amplifier. The slope efficiency is measured to be 71.6%.