Abstract: In one or more embodiments, an optical fiber coupler for coupling pump radiation into a rectangular optical fiber includes a fiber section and a pump fiber. The fiber section includes a core having a high aspect ratio cross-section and an interface section. The core is positioned in contact with first and second signal claddings to form reflective boundaries at fast-axis boundaries of the core. The pump fiber is side coupled to the fiber section via the interface section, and configured to couple the pump radiation into the fiber section.

Abstract: A coupler and method of coupling a signal beam between from a circular-core fiber to a rectangular-core cross section fiber includes providing an optical coupler having an optical core with a high-aspect ratio cross section at one end and a circular cross section at an opposite end to receive a signal beam having a circular cross section. The signal beam is propagated from the circular fiber to the rectangular-core cross section fiber in a narrow, fast-axis direction while maintaining the size and divergence of the signal beam as it propagates. The signal beam is expanded in size while producing a collimated beam from the circular cross section end to the rectangular-core cross section end in a wide, slow-axis direction.

Abstract: A coupler and method of coupling a signal beam between from a circular-core fiber to a rectangular-core cross section fiber includes providing an optical coupler having an optical core with a high-aspect ratio cross section at one end and a circular cross section at an opposite end to receive a signal beam having a circular cross section. The signal beam is propagated from the circular fiber to the rectangular-core cross section fiber in a narrow, fast-axis direction while maintaining the size and divergence of the signal beam as it propagates. The signal beam is expanded in size while producing a collimated beam from the circular cross section end to the rectangular-core cross section end in a wide, slow-axis direction.

Abstract: In one or more embodiments, an optical fiber coupler for coupling pump radiation into a rectangular optical fiber includes a fiber section and a pump fiber. The fiber section includes a core having a high aspect ratio cross-section and an interface section. The core is positioned in contact with first and second signal claddings to form reflective boundaries at fast-axis boundaries of the core. The pump fiber is side coupled to the fiber section via the interface section, and configured to couple the pump radiation into the fiber section.