Abstract: The present invention includes a sheet material, a first optical fiber, a second optical fiber optically coupled to the first optical fiber in portions thereof, and an optical fiber coupler constituted in the portions where the two optical fibers are coupled, and those of the first and second optical fibers, and the optical fiber coupler are integrally held in the sheet material.

Abstract: A structure for retaining an optical fiber, capable of not only handling a long optical fiber as one piece without causing the optical fiber as a whole to get loose but also reducing an area occupied by the optical fiber and retaining the same stably without causing micro-bending thereof to occur, wherein the optical fiber (1) is arranged so as to form planarly staggered turning portions thereof without causing intersecting parts to occur, a plurality of similar planarly staggered turning portions of the optical fiber being laminated in the same position in the direction of the thickness thereof which is at right angles to a plane on which the optical fiber is arranged, the resultant optical fiber (1) being generally retained in a sheet-like state by a fixing material (2), such as a bonding agent and a film.

Abstract: The present invention includes a sheet material, a first optical fiber, a second optical fiber optically coupled to the first optical fiber in portions thereof, and an optical fiber coupler constituted in the portions where the two optical fibers are coupled, and those of the first and second optical fibers, and the optical fiber coupler are integrally held in the sheet material.

Abstract: An optical fiber coupler for optical fiber amplifier use in the field of optical communications is provided. The optical fiber coupler comprises: a rare earth-doped fiber as an optical amplifying element; a quasi rare earth-doped fiber for entrance of input signal light; a fused-stretch fiber portion as a multiplexing element which connects a part of the rare earth-doped fiber and a parts the quasi rare earth-doped fiber, wherein the fused-stretch fiber portion formed by stretched a fused mixture of parts of the rare earth-doped fiber and the quasi rare earth-doped fiber; and a single mode fiber which is jointed at a fused joint portion to another shortened rare earth-doped fiber connected to the fused-stretch fiber portion on a side connected by the quasi rare earth-doped fiber. The quasi rare earth-doped fiber has substantially equal propagation constant to the rare earth-doped fiber without substantially containing rare earth elements.