Optical fiber for optical amplifier and fiber optic amplifier

#1. Field of the Invention

#The present invention relates to an optical fiber amplifier for receiving pumping light and signal light, amplifying the signal light, and outputting thus amplified signal light; and an optical fiber for optical amplification employed in this optical fiber amplifier. In particular, the present invention relates to an optical fiber for optical amplifier in which at least a part of its core is doped with erbium, and an optical fiber amplifier using this optical fiber.

#2. Related Background Art

#FIGS. 1 to 3 are schematic views showing the overall configurations of different embodiments of the optical fiber amplifier in accordance with the present invention, respectively;

#FIG. 4A is a vertical sectional view of an optical fiber for optical amplification in accordance with the present invention, whereas FIG. 4B is a transverse sectional view thereof;

#FIG. 5A is a vertical sectional view of another embodiment of the optical fiber for optical amplification in accordance with the present invention, whereas FIG. 5B is a transverse sectional view thereof;

#In the following, embodiments of the present invention will be explained in detail with reference to the accompanying drawings. To facilitate the comprehension of the explanation, the same reference numerals denote the same parts, where possible, throughout the drawings, and a repeated explanation will be omitted.

#FIGS. 1 to 3 are schematic views showing the respective configurations of different embodiments of the optical fiber amplifier in accordance with the present invention. Each of the embodiments is configured such that signal light to be amplified is inputted from the left end of the drawing and the amplified signal light is outputted from the right end. Each of the respective optical fiber amplifiers 10a, 10b, 10c shown in FIGS. 1 to 3 has an optical fiber 1 for optical amplification in accordance with the present invention, which is an amplification medium for amplifying the signal light. Optical isolators 4A, 4B for suppressing the oscillation of optical fiber amplifier are disposed on the input and output end sides of the signal, respectively. Further provided are pumping light sources 2A and/or 2B for generating pumping light in a 0.98 μm band or 1.48 μm band, and a optical multiplexer/demultiplexer 3A and/or 3B for introducing the pumping light generated in the pumping light source 2A and/or 2B into the optical fiber 1 on which the signal lights are incident.

#Depending on from which direction the pumping light is introduced into the optical fiber 1, the optical amplifiers are roughly classified into three types. The optical amplifier 10a in which signal light and pumping light are combined together and guided to the optical fiber 1 as shown in FIG. 1 is referred to as forward pumping system. The optical fiber amplifier 10b in which pumping light is introduced from the direction opposite to the signal light as shown in FIG. 2 is referred to as backward pumping system. And the optical fiber amplifier 10c in which pumping light is introduced from both ends of the optical fiber 1 as shown in FIG. 3 is referred to as bidirectional pumping system. A plurality of these amplifiers may be combined in series to constitute an amplifier section.