Abstract: An apparatus and method that provides management and cooling of an optical fiber by looping the optical fiber around the inner surface of a heat-conductive cylinder and around the outer surface of the heat-conductive cylinder, such that the optical fiber enters and exits the heat-conductive cylinder on substantially the same plane. Some embodiments use a continuous groove on the inside and outside of the cylinder for guiding and managing the optical fiber. Some embodiments use a plurality of protruding fiber guides for guiding and managing the optical fiber. Some embodiments use an integrated tube for guiding and managing the optical fiber. In some embodiments, the optical fiber looped on the inner surface and outer surface are spaced apart substantially equally. In some other embodiments, the optical fiber loops are spaced further apart for portions of the fiber carrying higher power.

Abstract: A method and apparatus is described that use an index-of-refraction profile having a significant central dip in refractive index (or another tailored index profile) within the core of a gain fiber or a gain waveguide on a substrate. The benefits of this central dip (more power with a given mode structure) are apparent when an input beam is akin to that of a Gaussian mode. In some embodiments, the invention provides a fiber or a substrate waveguide having an index profile with a central dip, but wherein the device has no doping. Some embodiments use a central dip surrounded by a higher-index ring in the index of refraction of the core of the fiber, while other embodiments use a trench between an intermediate-index central core portion and the ring, or use a plurality of rings and/or trenches. Some embodiments use an absorber in at least one core ring.

Abstract: An apparatus and method for generating a mode-scrambled optical signal. A laser beam source directs an optical signal into a free end of a first segment of multimode fiber comprising a graded-index (GI) fiber core at an offset from the centerline of the core, generating an offset-launch condition. The first segment of multimode fiber is operatively coupled into a second segment of multimode fiber comprising a step-index (SI) fiber core. As the offset-launched optical signal passes through the first and second segments of multimode fiber, the optical signal is converted into a mode-scrambled optical signal having a substantially-filled numerical aperture.

Abstract: An apparatus and method determines light transmission through a window. The window may be a single-pane or a double-pane window, and may or may not have coatings on its interior/exterior surfaces. Light transmission through the window can be measured based on power levels of light incident on the window and light reflected from the window. Such measurements can be performed for a wireless optical telecommunication system, in situations where it may be difficult or impossible to access both sides of a window to place or retrieve measurement equipment.