Multi-port coupler, optical amplifier, and fiber laser

摘要

A multi-port coupler (2) for coupling a pumping light source to a cladding pump fiber (3) for optical amplification, includes a central signal fiber (5) and a plurality of pumping fibers (4) arranged around the central signal fiber (5), the central signal fiber (5) and the plurality of pumping fibers (4) being unified and a front side is reduced in diameter, wherein an emitted light confining waveguide part (7) is provided around a core (6) of the signal fiber (5) located at the center, and the emitted light confining waveguide part (7) whose outer diameter is larger than that of the core (6) has a higher refractive index than a cladding (8) and a lower refractive index than the core (6) and the emitted light confining waveguide part (7) is formed continuously from a splicing point of the cladding pump fiber (3) to a coupler front end branched into multiple fibers (4 and 5).