Abstract: A highly nonlinear optical fiber having an improved stimulated Brillouin scattering threshold is provided. The fiber includes a central core region made substantially from silica doped with aluminum, a trench region surrounding the central core region, and a silica cladding surrounding the trench region. The refractive index profile of the fiber is optimized. A refractive index difference of the central core region relative to the cladding (?n+) is less than 26×10?3, and more preferably at or near 21×10?3. A refractive index difference of the trench region relative to the cladding (?n?) is less than ?5×10?3. The trench region is preferably doped with fluorine. The aluminum doping level of the central core region is preferably less than 14 wt % Al. A fiber doped with aluminum having this refractive index profile exhibits a significantly higher figure of merit (Pth?Leff) than conventional germanium-doped fibers.

Abstract: A rare earth doped optical fiber amplifier is configured to have an enlarged core region and a trench formed adjacent to the core, where at least an inner portion of the trench is also formed to include a rare earth dopant. The presence of the rare earth dopant in the inner region of the cladding minimizes transient power fluctuations within the amplifier as the number of optical signals being amplified changes. The addition of rare earth dopant to the cladding increases the overlap between the pump, signal and the rare earth ions and thus improves the gain efficiency for the optical signal. The relatively large core diameter increases the saturation power level of the rare earth dopant and decreases the transients present in the gain as the input signal power fluctuates.

Abstract: A highly nonlinear optical fiber having an improved stimulated Brillouin scattering threshold is provided. The fiber includes a central core region made substantially from silica doped with aluminum, a trench region surrounding the central core region, and a silica cladding surrounding the trench region. The refractive index profile of the fiber is optimized. A refractive index difference of the central core region relative to the cladding (?n+) is less than 26×10?3, and more preferably at or near 21×10?3. A refractive index difference of the trench region relative to the cladding (?n?) is less than ?5×10?3. The trench region is preferably doped with fluorine. The aluminum doping level of the central core region is preferably less than 14 wt % Al. A fiber doped with aluminum having this refractive index profile exhibits a significantly higher figure of merit (Pth?Leff) than conventional germanium-doped fibers.

Abstract: A rare earth doped optical fiber amplifier is configured to have an enlarged core region and a trench formed adjacent to the core, where at least an inner portion of the trench is also formed to include a rare earth dopant. The presence of the rare earth dopant in the inner region of the cladding minimizes transient power fluctuations within the amplifier as the number of optical signals being amplified changes. The addition of rare earth dopant to the cladding increases the overlap between the pump, signal and the rare earth ions and thus improves the gain efficiency for the optical signal. The relatively large core diameter increases the saturation power level of the rare earth dopant and decreases the transients present in the gain as the input signal power fluctuates.

Abstract: An optical fiber has a core region and a first cladding region surrounding the core. The first cladding region is doped to increase the fiber's refractive index volume. A second cladding region surrounds the first cladding region. The second cladding region is doped to reduce the fiber's cutoff wavelength, offsetting an increase in the fiber's cutoff wavelength caused by the first cladding region. An outer cladding surrounds the cutoff reduction region. In a further embodiment, the volume increasing region is doped to have a refractive index profile that is sloped to increase from the region's outer circumference towards its inner circumference. In another embodiment, the cutoff reduction region has a step refractive index profile that may have more than one section.

Abstract: An optical fiber has a core region and a first cladding region surrounding the core. The first cladding region is doped to increase the fiber's refractive index volume. A second cladding region surrounds the first cladding region. The second cladding region is doped to reduce the fiber's cutoff wavelength, offsetting an increase in the fiber's cutoff wavelength caused by the first cladding region. An outer cladding surrounds the cutoff reduction region. In a further embodiment, the volume increasing region is doped to have a refractive index profile that is sloped to increase from the region's outer circumference towards its inner circumference. In another embodiment, the cutoff reduction region has a step refractive index profile that may have more than one section.

Abstract: A pumped Raman fiber optic amplifier includes two optical fibers whose lengths are determined so that the fibers exhibit dispersions of substantially equal magnitude and opposite sign at the wavelength of an input light signal. The fiber having the positive dispersion has a cylindrical core, an outer cladding, and a refractive index profile with respect to the outer cladding. The core has a diameter of between 3 and 6 microns (&mgr;m) and a difference (&Dgr;n) between the index of the core and the cladding is between 0.015 and 0.035. The index profile includes a trench region adjacent the circumference of the core, and the trench region has a width of between 1 and 4 &mgr;m and a &Dgr;n of between −0.005 and −0.015. The two fibers are slope matched so that the net dispersion of the amplifier remains substantially zero over a broad wavelength interval.

Abstract: An optical fiber suited for dispersion compensation with simultaneous Raman amplification. The fiber has a central core and an index profile that defines successively concentric regions radially outward of the core. The core has a diameter of between 2 and 5 microns (&mgr;m) and a refractive index difference (&Dgr;n) with respect to the outer cladding of between 0.012 and 0.035. A trench region adjacent the core is between 2 and 6 &mgr;m wide and has a negative &Dgr;n of between −0.015 and −0.003. A ring region adjacent the trench region is between 1 and 5 &mgr;m wide and has a &Dgr;n of between 0.001 and 0.015, and an inner cladding surrounding the ring region has a width of between zero and 5 &mgr;m and a &Dgr;n of between −0.011 and 0.001. A dispersion slope compensating module (DSCM) including the fiber obtains a relatively high Raman gain with respect to conventional DSCMs that are pumped for Raman amplification.

Abstract: A pumped Raman fiber optic amplifier includes two optical fibers whose lengths are determined so that the fibers exhibit dispersions of substantially equal magnitude and opposite sign at the wavelength of an input light signal. The fiber having the positive dispersion has a cylindrical core, an outer cladding, and a refractive index profile with respect to the outer cladding. The core has a diameter of between 3 and 6 microns (&mgr;m) and a difference (&Dgr;n) between the index of the core and the cladding is between 0.015 and 0.035. The index profile includes a trench region adjacent the circumference of the core, and the trench region has a width of between 1 and 4 &mgr;m and a &Dgr;n of between −0.005 and −0.015. The two fibers are slope matched so that the net dispersion of the amplifier remains substantially zero over a broad wavelength interval.

Abstract: The specification describes rare earth doped fiber amplifier devices for operation in the extended L-band, i.e. at wavelengths from 1565 nm to above 1610 nm. High efficiency and flat gain spectra are obtained using a high silica based fiber codoped with Er, Al, Ge, and P and an NA of at least 0.15.

Abstract: The specification describes rare earth doped fiber amplifier devices for operation in the extended L-band, i.e. at wavelengths from 1565 nm to above 1610 nm. High efficiency and flat gain spectra are obtained using a high silica based fiber codoped with Er, Al, Ge, and P and an NA of at least 0.15.

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: A method of producing an active optical waveguide having asymmetric polarization, said method comprising the steps of (a) providing an active optical waveguide (10) comprising: (i) a transverse refractive index profile (21) comprising a guiding region (11), an intermediate region (13), and a non-guiding region (12); (ii) a transverse photorefractive dopant profile (31) comprising a constant or graded photorefractive dopant concentration within at least one of the guiding, non-guiding and intermediate regions, except that the photorefractive dopant is not located solely in the guiding region; and (iii) exhibiting in said guiding region, intermediate region, or both, light guiding modes having different polarizations; and (b) exposing at least a part (10a, 10b) of the active optical waveguide to an effective transverse illumination of light (20) reacting with the photorefractive dopant and modifying said transverse refractive index profile; said part of the active optical waveguide being exposed to a fluence se