Technical Improvements in the Structure of Low-Loss High-Power Signal Combiner

Several technical improvements are presented to achieve a high transmission efficiency signal combiner. A signal combiner is fabricated based on the tapered fiber bundle technique. A thin fused-silica capillary tube is utilized to bundle fibers, and the diameter of the input fibers is reduced by hydrofluoric acid to have a desired taper ratio. The main taper parameters, taper ratio, taper length, and degree of fusion of TFB are selected so that the combiner does have high transmission efficiency. The combiner is tested up to 3.04 kW by incoherently combining of three fiber lasers with transmission efficiency more than 99%. The thermal analysis shows that the combiner temperature remains at room temperature without need for cooling at full power.