Amplification optical fiber, fiber optic amplifier, optical transmitter, and optical communication system

摘要

This invention relates to an amplification optical fiber which requires no gain equalizer and has a flat gain spectrum and high polarization extinction ratio, and the like. The amplification optical fiber has a core region included in a light propagation region through which signals having different wavelengths propagate, a cladding region around the core region, and a polarization maintaining structure for maintaining the polarized states of the signals. The amplification optical fiber is mainly comprised of silica glass, and Er and Al of 4 wt % or more are doped into at least part of the light propagation region including the core region.