By exciting dopant ions in a fiber and utilizing the process of stimulated emission, optical amplifiers can amplify optical signals directly, enabling long-distance and high-speed data transmission in fiber-optic networks. An illustration of the effective gainis given below. An optical amplifier may be thought of as a laser without an optical cavity, or one in which feedback from the cavity is suppressed. Typically, inputs and outputs are laser beams (very rarely other types of light beams), either propagating as Gaussian beams in free space or in a fiber.