Polarized wave holding optical fiber, production method therefor, connection method therefor, optical amplifier, laser oscillator and polarized wave holding optical fiber coupler

A polarization-maintaining optical fiber wherein a plurality of core portions, each of which has a high refractive index, and each of which has a relative refractive index of 0.15.about.3.0%, are provided substantially longitudinally in parallel with a center axis of said optical fiber, and substantially in an array with the center axis in cross section of said optical fiber, and wherein said core portions cooperate to propagate a single fundamental mode.

A polarization-maintaining optical fiber coupler formed by bringing into contact, heating, fusing and elongating two or more polarization-maintaining optical fibers in which a plurality of core portions each of which has a high refractive index are provided substantially longitudinally in parallel with a center axis of said optical fiber, and substantially in an array with the center axis in the cross section of said optical fiber, said core portions cooperating to propagate a single fundamental mode.

A polarization-maintaining optical fiber connection method characterized in that, when fusion connecting polarization-maintaining optical fibers in which a plurality of core portions each of which has a high refractive index are provided substantially longitudinally in parallel with a center axis of said optical fiber, and substantially in an array with the center axis in the cross section of said optical fiber, said core portions cooperating to propagate a single fundamental mode, the vicinity of the connection point is heated before or after connection.

A rare-earth-doped polarization-maintaining optical fiber which has a polarization-maintaining function wherein a plurality of core portions each of which has a high refractive index are provided substantially longitudinally in parallel with a center axis of said optical fiber, and substantially in an array with the center axis in the cross section of said optical fiber, said core portions cooperating to propagate a single fundamental mode, and wherein either one or both of the core portions and the cladding portion which is in a region having a low refractive index interposed between core portions are doped with a rare earth element.

A polarization-maintaining optical fiber, wherein a plurality of core portions, each of which has a high refractive index, are provided substantially longitudinally in parallel with a center axis of said optical fiber, and substantially in an array with the center axis in cross section of said optical fiber, symmetrically with respect to the center axis of said optical fiber, and wherein said core portions cooperate to propagate a single fundamental mode.

A polarization-maintaining optical fiber coupler formed by bringing into contact, heating, fusing, and elongating two or more polarization-maintaining optical fibers in which a plurality of core portions, each of which has a high refractive index, and each of which has a relative refractive index of 0.15.about.3.0%, are provided substantially longitudinally in parallel with a center axis of said optical fiber, and substantially in an array with the center axis in cross section of said optical fiber, said core portions cooperating to propagate a single fundamental mode.

A polarization-maintaining optical fiber coupler formed by bringing into contact, heating, fusing, and elongating two or more polarization-maintaining optical fibers in which a plurality of core portions, each of which has a high refractive index, are provided substantially longitudinally in parallel with a center axis of said optical fiber, and substantially in an array with the center axis in cross section of said optical fiber, symmetrically with respect to the center axis of said optical fiber, said core portions cooperating to propagate a single fundamental mode.