Abstract: To couple the elliptical mode field light beam of a laser radiation source to a circularly symmetric single-mode optical fiber, the end of the fiber is provided with an anamorphic lens. The double wedge-shaped lens provides high coupling efficiency and is easily constructed. Other anamorphic lenses are also disclosed. A single wedge lens can provide high coupling efficiency if it is formed on the end of a coupling fiber which has a core that is elliptically-shaped in cross-section, the line of intersection of the two surfaces forming the lens being aligned with the major axis of the elliptical fiber core.

Abstract: Disclosed is a fiber amplifier including a gain fiber and a source of pump power having a wavelength .lambda..sub.p coupled to one end thereof. A signal of wavelength .lambda..sub.s is introduced into a first end of the gain fiber, and an amplified signal of wavelength .lambda..sub.s is coupled from the second end thereof. The signal can traverse an undesired secondary path as well as a preferred primary path to the amplifier output. To prevent light of wavelength .lambda..sub.s from traversing the secondary path and thus increasing the amplifier noise figure, the amplifier includes attenuating fiber means for attenuating that portion of the signal of wavelength .lambda..sub.s that propagates in the secondary path.

Abstract: An optical system for coupling a laser radiation source to a circularly symmetric single-mode optical fiber. The laser radiation source produces a beam of light having an elliptical mode field. The input end of a coupling fiber, which has a core that is elliptically-shaped in cross-section, is situated in light receiving relationship with respect to the source. The coupling fiber is oriented with respect to the source such that the mode field of the source is aligned with the coupling fiber core to provide the most efficient coupling of light from the source to the fiber. Means such as an evanescent coupler couples light from the output end of the fiber to the circularly symmetric fiber.

Abstract: Disclosed is a fiber amplifier system in which a gain fiber is operatively combined with a fiber optic coupler having first and second coupler optical fibers. The coupler fibers are fused together along a portion of their lengths to form a wavelength dependent coupling region whereby most of the light power of a wavelength .lambda..sub.s couples between them, and most of the light power of a wavelength .lambda..sub.p that is introduced into the first fiber remains in it. The mode field diameter of the first coupler fiber is substantially matched to that of the gain fiber and is smaller than that of the second coupler fiber. One end of the first coupler fiber is spliced to the gain fiber. A transmission fiber is spliced to the second coupler fiber, and a laser diode introduces pumping light of wavelength .lambda..sub.p to the first coupler fiber. The fiber optic coupler preferably includes an elongated body of matrix glass through which the first and second coupler fibers extend.

Abstract: The present invention relates to a method of attaching an optical fiber alignment ferrule to a connector body, the first end of which is lens-shaped. The body has an indented region in the second end thereof opposite the lens, the indented region being centered on the optical axis of the lens. The body is mounted in a cavity in an alignment fixture which also includes a bore that is aligned with the cavity. The bore is so positioned that when a connector body is mounted in the cavity, the axis of the bore is coaxial with the optical axis of the lens. A rigid alignment rod is slidably mounted in the bore so that the rod is capable of only longitudinal movement along its axis. One end of the rod is inserted through the hole in a tubular ferrule. The rod is advanced toward the connector body until the rod contacts the bottom of the indented region. The ferrule is moved along the rod until it contacts the second surface of the body. The ferrule is then bonded to the body.