Abstract: A mode converter includes first and second optical waveguides and a GRIN fiber lens. The GRIN fiber lens is attached to both the first and the second waveguides.

Abstract: A method for fabricating a GRIN fiber includes forming a tube of silica-glass having a tubular core and a concentric tubular cladding adjacent and external to the tubular core. The core has a dopant density with a radially graded profile. The method includes partially collapsing the tube by applying heat thereto. The partially collapsed tube has a central channel. The method includes passing a glass etchant through the central canal to remove an internal layer of silica glass, and then, collapsing the etched tube to a rod-like preform.

Abstract: A technique for measuring the modal power distribution of an optical source (for example, a laser) launching pulses into a multimode fiber involves a characterization of the multimode fiber itself in terms of its differential modal delay. A reverse differential mode delay measurement is then performed to characterize the interaction of the optical source with the multimode fiber. By knowing these characteristics, the modal power distribution of the source into the fiber can then be determined by using a reconstruction algorithm.

Abstract: An optical system for monitoring or imaging a sample includes a probe, an optical splitter or circulator, and an optical detector. The probe includes an optical fiber and a GRIN fiber-size lens fused to one end of the fiber. The optical splitter or circulator receives light from a source and directs a portion of the received light to the fiber. The optical detector is coupled to receive a portion of light collected from the sample by the GRIN fiber-size lens and is configured determine a characteristic of the sample from the received light.

Abstract: A mode converter includes first and second optical waveguides and a GRIN fiber lens. The GRIN fiber lens is attached to both the first and the second waveguides.

Abstract: Embodiments of the invention include a singlemode optical fiber having an antimony (Sb) doped core region, a suitable cladding region formed on the core region, and one or more gratings written in the optical fiber. Optical fibers manufactured according to embodiments of the invention provide faster growth of grating strength, higher thermal stability, and longer photosensitive wavelength compared to conventional Ge doped silica optical fibers. The optical fiber is fabricated for applications such as fiber grating applications where the index of the core is modulated by UV radiation. Also, the addition of Sb in the core region of the singlemode optical fiber provides higher temperature (e.g., greater than 100° C.) applications of fiber gratings and a reduced degradation of the band rejection efficiency. Also, the optical fibers are more conducive to direct and non-destructive grating writing over polymer jackets with a longer photosensitive wavelength in the UV range.

Abstract: A GRIN fiber lens has a silica-glass core whose refractive index has a radial profile. The profile has a radial second derivative whose average magnitude in the core is less than about 1.7×10−6 microns−2 times the value of the refractive index on the axis of the GRIN fiber lens.

Abstract: A GRIN fiber lens has a silica-glass core whose refractive index has a radial profile. The profile has a radial second derivative whose average magnitude in the core is less than about 1.7×10−6 microns−2 times the value of the refractive index on the axis of the GRIN fiber lens.

Abstract: Our method of making high bandwidth silica-based multimode optical fiber comprises provision of a non-circular preform, and drawing fiber of chiral structure from the preform. The non-circular preform can be made by maintaining the inside of the tubular preform under reduced pressure during at least part of the collapse, resulting in a non-circular core and cladding. It can also be made by removal (e.g., by grinding or plasma etching) of appropriate portions of the preform, resulting in a circular core and non-circular cladding. In the latter case, fiber is drawn at a relatively high temperature such that, due to surface tension, the cladding assumes substantially circular shape and the core assumes a non-circular shape. The chiral structure is imposed on the fiber in any appropriate way, e.g., by twisting during fiber drawing the fiber alternately in clockwise and couterclockwise sense relative to the preform.

Abstract: A Raman amplified dispersion compensation module has a first dispersion compensating fiber (DCF) with an input end and an output end. The first DCF has a known Raman gain coefficient (gr(&lgr;)), Raman effective fiber area (AReff), and dispersion characteristic. An input end of a second DCF is arranged to receive light signals from the output end of the first DCF. The second DCF has a known gain coefficient and effective area, and a dispersion characteristic selected to cooperate with that of the first DCF to produce a desired total module dispersion. The lengths of the DCFs are selected in a manner that optimizes the overall module gain.

Abstract: Disclosed is a method of launching a light beam from a semiconductor laser into a multimode optical fiber, as well as apparatus for launching the light beam. The light beam is directed at nominally the center of the input face of the multimode fiber such that the (unguided) light beam makes an angle &thgr;b (typically in the range 1-20 degrees) with the direction perpendicular to the input face of the multimode fiber. The angle &thgr;b is selected such that at least one lower order mode of the guided radiation in the multimode fiber is substantially not excited in the fiber, with at least some higher order modes being substantially excited. Several specific embodiments are disclosed.

Abstract: Embodiments of the invention include an optical communications system including one or more optical transmission devices, one or more optical receiving devices, and at least one positive dispersion optical fiber coupled therebetween. The fiber includes a doped core region with an index of refraction n1, a cladding region with an index of refraction n2, and first and second annular rings or regions therebetween with indices of refraction n3 and n4, respectively. The various regions are manufactured in such a way that the refractive index value ranges are: 0.14<(n1−n2)/n2<0.31, −0.19<(n3−n2)/n2<−0.02, and −0.20<(n4−n2)/n2<−0.08. The fibers exhibit a chromatic dispersion greater than 20±2.0 ps/(nm-km) and a dispersion slope less than 0.062 ps/(nm2-km) at a wavelength of 1550 nm. Also, the fibers have a relatively large effective core area, Aeff, e.g., greater than 100.0 &mgr;m2, and a relative dispersion slope (RDS) less than 0.0032 nm−1.

Abstract: Embodiments of the invention include an optical communications system including one or more optical transmission devices, one or more optical receiving devices, and at least one positive dispersion optical fiber coupled therebetween. The fiber includes a doped core region with an index of refraction n1, a cladding region with an index of refraction n2, and first and second annular rings or regions therebetween with indices of refraction n3 and n4, respectively. The various regions are manufactured in such a way that the refractive index value ranges are: 0.14<(n1−n2)/n2<0.31, −0.19<(n3−n2)/n2<−0.02, and −0.20<(n4−n2)/n2<−0.08. The fibers exhibit a chromatic dispersion greater than 20±2.0 ps/(nm-km) and a dispersion slope less than 0.062 ps/(nm2-km) at a wavelength of 1550 nm. Also, the fibers have a relatively large effective core area, Aeff, e.g., greater than 100.0 &mgr;m2, and a relative dispersion slope (RDS) less than 0.0032 nm−1.

Abstract: A mode converter includes first and second optical waveguides and a GRIN fiber lens. The GRIN fiber lens is attached to both the first and the second waveguides.

Abstract: A GRIN fiber lens has a silica-glass core whose refractive index has a radial profile. The profile has a radial second derivative whose average magnitude in the core is less than about 1.7×10−6 microns−2 times the value of the refractive index on the axis of the GRIN fiber lens.

Abstract: An optical system for monitoring or imaging a sample includes a probe, an optical splitter or circulator, and an optical detector. The probe includes an optical fiber and a GRIN fiber-size lens fused to one end of the fiber. The optical splitter or circulator receives light from a source and directs a portion of the received light to the fiber. The optical detector is coupled to receive a portion of light collected from the sample by the GRIN fiber-size lens and is configured determine a characteristic of the sample from the received light.

Abstract: Our method of making high bandwidth silica-based multimode optical fiber comprises provision of a non-circular preform, and drawing fiber of chiral structure from the preform. The non-circular preform can be made by maintaining the inside of the tubular preform under reduced pressure during at least part of the collapse, resulting in a non-circular core and cladding. It can also be made by removal (e.g., by grinding or plasma etching) of appropriate portions of the preform, resulting in a circular core and non-circular cladding. In the latter case, fiber is drawn at a relatively high temperature such that, due to surface tension, the cladding assumes substantially circular shape and the core assumes a non-circular shape. The chiral structure is imposed on the fiber in any appropriate way, e.g., by twisting during fiber drawing the fiber alternately in clockwise and couterclockwise sense relative to the preform.

Abstract: A method is disclosed for qualifying a multimode optical fiber 150 for bandwidth performance when used with a particular laser source. The method combines the modal power distribution (MPD) excited by a particular laser source with the differential mode delay (DMD) characteristic of the fiber. The DMD of the fiber is measured by injecting test pulses into one end of the fiber and detecting the resulting output pulse(s) at the other end. The test pulses are adapted to excite only a small number of the modes supported by the fiber. The test pulses are scanned across the core of the fiber at close intervals with the output pulse(s) stored at each radial position. A weighted sum of the output pulses is formed to determine a time-domain impulse response, where the weighting used corresponds to the MPD excited by the laser source. Bandwidth is then determined by standard methods for transforming the impulse response into the frequency domain.

Abstract: A fiber optic system comprises an optical transmitter, an optical receiver, and an optical fiber transmission path that optically couples the transmitter and the receiver to one another. The transmission path includes a first section that has negative dispersion at an operating wavelength &lgr;0 greater than about 1300 nm and a second section that includes a MOF. The MOF has relatively large anomalous dispersion at &lgr;0 and is sufficiently long to compensate the accumulated negative dispersion in the first section. In one embodiment the MOF comprises a core, a lower index cladding that includes one or more layers of air holes surrounding the core, characterized in that the diameter of the core is less than about 8 &mgr;m and the difference in effective refractive index between the core and cladding is greater than about 0.1 (10%). Preferably, the cladding contains no more than 2 layers of air holes and the distance between the nearest edges of adjacent air holes is less than about 1 &mgr;m.

Abstract: A fiber optic system comprises an optical transmitter, an optical receiver, and an optical fiber transmission path that optically couples the transmitter and the receiver to one another. The transmission path includes a first section that has negative dispersion at an operating wavelength &lgr;0 greater than about 1300 nm and a second section that includes a MOF. The MOF has relatively large anomalous dispersion at &lgr;0 and is sufficiently long to compensate the accumulated negative dispersion in the first section. In one embodiment the MOF comprises a core, a lower index cladding that includes one or more layers of air holes surrounding the core, characterized in that the diameter of the core is less than about 8 &mgr;m and the difference in effective refractive index between the core and cladding is greater than about 0.1 (10%). Preferably, the cladding contains no more than 2 layers of air holes and the distance between the II nearest edges of adjacent air holes is less than about 1 &mgr;m.