Abstract: An optical waveguide designed to generate positive dispersion when operated in a high order mode. The optical waveguide in one embodiment is designed to generate positive dispersion slope, in another embodiment to generate negative dispersion slope and in yet another embodiment nominally zero dispersion slope. In one embodiment the high order mode is the LP02 mode and in another embodiment the high order mode is the LP03 mode. In another embodiment the optical waveguide is a few mode fiber. In an exemplary embodiment the optical waveguide is used in combination with a mode transformer, such as a transverse mode transformer to achieve the desired high order mode.

Abstract: A method of measuring dispersion in an optical fiber from one end is disclosed. An optical measurement signal comprising timed pulses is input into one end of the fiber, and a small loop is formed at the point to which total dispersion is to be measured. In one embodiment the loop is formed so as to increase the amount of detectable light that escapes the fiber at the loop, and the escaping light pulses are monitored by a free space detector. The wavelength of the optical measurement signal is varied, and the change in propagation delay of the detected optical pulses is measured, thus indicating the dispersion. In a second embodiment the loop is formed so as to increase the amount of loss in the optical measurement signal, and an OTDR is utilized.

Abstract: The present invention relates in one aspect, to a refractive index profile designed to support higher order spatial modes, and in particular the LP02 spatial mode in an optical waveguide. The waveguide exhibits negative dispersion and negative dispersion slope and negative third order dispersion over the operating wavelength. In one embodiment, the profile is designed with a reduced refractive index depression in the center core region, and is intended to enhance the properties of the dispersion compensating waveguide. In addition, the refractive index profile of the present invention supports the LP02 mode. A limited mode dispersion compensating optical waveguide according to the present invention includes a center core portion having a center core refractive index. The waveguide also includes an outer core portion surrounding the center core portion and having an outer core refractive index that is greater than the center core refractive index.

Abstract: An optical waveguide supporting a plurality of modes including an annulus which attenuates a desired mode to a lesser degree than any other mode in the plurality of modes. In one embodiment, the annulus is disposed in the core of the waveguide. In another embodiment, the annulus is concentric about the core. In another embodiment, the annulus has a predetermined width and radius. In yet another embodiment the optical waveguide includes an annulus that is disposed at a radial position corresponding to a region in the core in which the desired mode has substantially no energy. In yet another embodiment the desired mode includes the LP02 mode. In another embodiment, the annulus includes a scattering material. In still another embodiment, the annulus includes a conductive dopant material. Another embodiment includes a sharp change of refractive index within the core. Still other embodiments include disposing a region of increased refractive index in the core of the waveguide to attenuate undesired modes.

Abstract: The invention relates to method and apparatus for transmitting an optical signal having optical energy substantially in a high order spatial mode. The optical waveguide, in one embodiment, includes a few mode fiber designed to have specific transmission characteristics for supporting the single high order spatial mode, and the few mode fiber transmits the single high order spatial mode. The optical waveguide, in one embodiment, has a dispersion and a dispersion slope for a given transmission bandwidth. Another aspect of the invention includes a method for transmitting an optical signal having optical energy substantially in a single high order spatial mode. The method includes the steps of providing a few mode fiber, which supports optical energy in the single high order spatial mode. In one embodiment, the single high order spatial mode is the LP02 spatial mode In another embodiment, the few mode fiber supports an optical signal having optical energy having less than twenty spatial modes.

Abstract: A transverse spatial mode transformer for transforming an optical signal between different spatial modes is described. The transformer is based on a spatially selective change of the phase of the optical signal wavefront relative to the initial wavefront. As the phase-adjusted optical signal propagates, the transverse intensity distribution changes to correspond to the new spatial mode. The transformer can be used to change the lower order spatial mode of an optical signal to a higher order spatial mode appropriate for a dispersion compensated fiber optic communication system. The transformer can also be used to change a higher order spatial mode to a lower order spatial mode.

Abstract: An optical communication system with dispersion compensation uses transverse mode transformers and a chromatic dispersion compensation optical fiber. A low order spatial mode optical signal from a communication fiber is transformed by a transverse mode transformer into a higher order spatial mode before being injected into a chromatic dispersion compensation optical fiber. The optical signal exiting the compensation fiber is then transformed back to a lower order spatial mode before being injected into a second communication fiber.

Abstract: The invention relates to apparatus and methods for transforming a spatial mode of an optical signal. The apparatus includes an optical phase element for imparting a predetermined spatially selective phase delay to the optical signal, and a mask in optical communication with the optical phase element. The mask, in one embodiment, includes an optically attenuating region disposed in a predetermined spatial pattern. In one aspect of the invention, the optical signal is transformed from a first spatial mode to a second spatial mode. In another aspect of the invention, the mask includes an absorbing material arranged in a predetermined spatial pattern. In yet another aspect of the invention, the mask includes a scattering material arranged in a predetermined spatial pattern. The invention also relates to a method for transforming a spatial mode of an optical signal. The method includes the step of receiving the optical signal having a first spatial mode with an intensity distribution and a phase.

Abstract: The invention relates to methods and apparatus for transmitting an optical signal having optical energy. The system, in one embodiment, includes at least one transmission span including an optical waveguide. The transmission span transmits substantially all of the optical energy in a single high order spatial mode. The optical waveguide, in one embodiment, has a dispersion and a dispersion slope for a given transmission bandwidth. In another embodiment, the invention further relates to an optical transmission system which includes a spatial mode transformer positioned to receive an optical signal. The spatial mode transformer transform the optical energy of the optical signal from a low order spatial mode to a high order spatial mode. The system further includes an optical transmission waveguide in optical communication with a spatial mode transformer, and the optical transmission waveguide transmits substantially all of the optical energy in the high order spatial mode.

Abstract: The present invention relates to a method for enabling reliable, consistent alignment of a beam of light eating the end of an optical fiber, which has been cut at a non-perpendicular angle, with a collimating lens. The method involves utilizing a spherical shape to generate two bores in the object which intersect the center at a predetermined angle. The predetermined angle is equivalent to the angle of the light beam exiting the end of the optical fiber.

Abstract: A dispersion compensation device uses at least two chromatic dispersion compensation fibers to compensate for chromatic dispersion present in an optical communication system. Two dispersion orders can be corrected using appropriate lengths of two serially coupled compensation fibers having different dispersion characteristics. The device can compensate for N additional orders of dispersion by using N additional compensation fibers with unique dispersion characteristics. The device can be coupled directly to a transmission fiber.

Abstract: An optical waveguide supporting a plurality of modes including an absorbing annulus which attenuates a desired mode to a lesser degree than any other mode in the plurality of modes. In one embodiment, the absorbing annulus is disposed in the core of the waveguide. In another embodiment, the annulus is concentric about the core. In another embodiment, the annulus has a predetermined width and radius. In yet another embodiment the desired mode includes the LP02 mode.