PUMPING ARRANGEMENT FOR FIBER AMPLIFIERS

摘要

An optical gain apparatus has a pump source providing pump energy at a pump wavelength to a gain medium that generates optical energy at a singal wavelength. To minimize disturbance from signal wavelengths appearing in a coupling path between the pump source and the gain medium, an optical attenuator is located in the coupling path that provides a significant degree of attenuation to signal wavelengths, while providing negligible attenuation of pump wavelengths. The attenuator may comprise a grating structure, such as a long period grating or a blazed grating. It may also comprise an angled coupling fiber that is oriented to reflect signal wavelengths out of the coupling path. The end of such a fiber would typically be formed into a microlens, such as a wedge-shaped lens or a biconic lens, and would preferably be coated with a material that is highly reflective at the signal wavelength, but anti-reflective at the pump wavelength. The microlens may also be angled relative to a longitudinal axis of the fiber. Other embodiments include the location of an attenuation component, such as scattering sites, absorbing material, or a refractive index change, at a radial position in the cladding of the optical fiber that affects the signal wavelength but not the pump wavelength.