Abstract: An optical module for supplying pump light for amplifying to-be-amplified light includes an pump light source, optical coupling means, and an optical guide section. The optical guide section optically connects the pump light source and the optical coupling means, and propagates the pump light from the pump light source, in multi-transverse-mode. The optical coupling means output the pump light from the optical guide section in multi-transverse-mode, and at least one of (i) at least one of end faces where the optical guide section and the optical coupling means are connected, (ii) an area between the end faces, and (iii) the optical guide section, has a loss medium of which transmission loss is greater in a wavelength of the to-be-amplified light than in a wavelength of the pump light. By this, an optical module which can stably supply the pump light to the optical amplification fiber can be provided.

Abstract: The present invention relates to an optical amplification module having a construction which effectively suppresses photodarkening, and to a laser light source including the same. The laser light source comprises a light source for outputting light to be amplified, and an optical amplification module. The optical amplification module comprises two types of optical amplification media having different rare earth element concentrations, and a pumping light source. The low concentration medium and the high concentration medium are disposed in the propagation direction of pumping light such that the population inversion of the low concentration medium is higher than that of the high concentration medium.

Abstract: The present invention relates to an optical amplifier with a structure for more effectively suppressing the over/undershoot in transient responses in high-speed AGC. This optical amplifier is an optical device for amplifying signal light inputted therein, and comprises a rare-earth-element-doped optical fiber, an optical coupler, a light-receiving section, a pumping light source, and a control section. In particular, as a typical structure of the optical amplifier, the rare-earth-element-doped optical fiber has a cutoff wavelength ?c set longer than the pumping light wavelength ?p but shorter than the signal light wavelength ?s, and mainly allows a pumping light component in a fundamental mode to propagate therethrough.

Abstract: The present invention relates to a Raman amplifier and the like which has a structure capable of easily improving the transient response characteristic without depending on the added/dropped signal channels. In the Raman amplifier, a pumping light source supplies forward pumping light of wavelength &lgr;p0 to a Raman-amplifying optical fiber. A pumping light source supplies N-channel backward pumping light of wavelengths &lgr;p1-&lgr;pN to the Raman-amplifying optical fiber. The wavelength &lgr;p0 of the forward pumping light is less than or equal to the shortest wavelength of the channel wavelengths &lgr;p1-&lgr;pN of the backward pumping light. In particular, the power of the backward pumping light and the power of the forward pumping light are arranged such that the effective length Leff of the Raman-amplifying optical fiber for the channel wavelengths &lgr;p1-&lgr;pN of the backward pumping light becomes longer than the actual length L.