Abstract: Embodiments of the invention include an optical fiber device such as a modulator, variable attenuator or tunable filter including an optical fiber having a core region, a cladding layer around the core region, and a controllable active material disposed in, e.g., capillaries or rings formed the cladding layer. The active materials include, e.g., electro-optic material, magneto-optic material, photorefractive material, thermo-optic material and/or materials such as laser dyes that provide tunable gain or loss. The application of, e.g., temperature, light or an electric or magnetic field varies optical properties of the active material, which, in turn, varies or affects the propagation properties of optical signals in the device. The optical device includes a tapered region that causes the core mode to spread into the cladding region and, simultaneously, allows the active material to be relatively close to the propagated modes, thus allowing interaction between the active material and the propagating modes.

Abstract: A thermally tunable optical fiber device comprises a length of optical fiber including a device disposed within a microcapillary heater. The microcapillary heater can include a thin film resistive heater. The fiber itself can optionally include a thin film resistive heater overlying the device, and a plurality of nested microcapillary tubes can optionally provide a plurality of successive concentric heaters overlying the device. The heaters films can be films with uniform, tapered or periodically varying thickness. The heaters can be single layer or multiple layer. Multiple layer films can be superimposed with intervening insulating layers or plural layers can be formed on different angular regions of the microcapillary. Thus one can provide virtually any desired temperature versus length profile along the fiber device.

Abstract: A unique waveguide structure is provided in which the waveguide contains individual scattering elements that are capable of being tuned to provide local refractive index variations, e.g., on a micron scale—which is on the order of wavelengths typically used for communication system. According to the invention, the waveguide contains a core region, a cladding region, and a solid or liquid material having the tunable scattering elements dispersed therein, where the material is disposed within the core and/or cladding regions, and/or on the exterior of the cladding region. Useful scattering elements include, for example, liquid crystals dispersed in a polymer (polymer-dispersed liquid crystals—PDLC) or electrophoretic particles dispersed in a liquid medium.

Abstract: Embodiments of the invention include an optical fiber device such as a modulator, variable attenuator or tunable filter including an optical fiber having a core region, a cladding layer around the core region, and a controllable active material disposed in, e.g., capillaries or rings formed the cladding layer. The active materials include, e.g., electro-optic material, magneto-optic material, photorefractive material, thermo-optic material and/or materials such as laser dyes that provide tunable gain or loss. The application of, e.g., temperature, light or an electric or magnetic field varies optical properties of the active material, which, in turn, varies or affects the propagation properties of optical signals in the device. The optical device includes a tapered region that causes the core mode to spread into the cladding region and, simultaneously, allows the active material to be relatively close to the propagated modes, thus allowing interaction between the active material and the propagating modes.

Abstract: In accordance with the invention, a modulated RZ pulse source comprises a modulated light source optically coupled to a stabilized Bragg grating filter and one or more optical taps. The light source is preferably modulated in power and frequency and has an adjustable channel wavelength &lgr;. The Bragg grating filter has a reflectivity bandwidth having a high slope reflectivity cutoff and is preferably tunable. A feedback arrangement responsive to the taps keeps the source channel wavelength &lgr; on the edge of the reflectivity bandwidth for shaping RZ pulses. When the Bragg grating is stabilized, the feedback system maintains &lgr; at a value linked to the grating reflectivity edge and, by overlapping at least part of the optical spectrum of the source, converts the modulated source light into RZ pulses with high extinction ratio (≧12 dB). The result is a high power, jitter-free RZ pulse source that is compact, inexpensive and power efficient.

Abstract: A multi-wavelength cascaded Raman resonator (“MWCRR”). The MWCRR has an optical source for pumping optical radiation centered around an input wavelength. The MWCRR further includes a Raman fiber having at least a first set of optical gratings for converting the pumped optical radiation to wavelengths other than the input wavelength. The Raman fiber also has at least one adjustable output coupler having a variable reflectivity for controlling the power of the optical radiation propagating from the at least one set of optical gratings at the wavelengths other than the input wavelength.

Abstract: The invention involves providing a microstructured fiber having a core region, a cladding region, and one or more axially oriented elements (e.g., capillary air holes) in the cladding region. A portion of the microstructured fiber is then treated, e.g., by heating and stretching the fiber, such that at least one feature of the fiber microstructure is modified along the propagation direction, e.g., the outer diameter of the fiber gets smaller, the axially oriented elements get smaller, or the axially oriented elements collapse. The treatment is selected to provide a resultant fiber length that exhibits particular properties, e.g., mode contraction leading to soliton generation, or mode expansion. Advantageously, the overall fiber length is designed to readily couple to a standard transmission fiber, i.e., the core sizes at the ends of the length are similar to a standard fiber, which allows efficient coupling of light into the microstructured fiber length.

Abstract: In accordance with the invention, a thermally tunable optical waveguide device is stabilized against ambient changes. Specifically, a feedback signal derived from a temperature-dependent resistance is used to stabilize the device with respect to ambient changes that could otherwise alter the temperature. Specific embodiments include resistance-heated tunable gratings.

Abstract: In accordance with the invention, an optical waveguide grating with an adjustable optical spacing profile comprises a waveguide grating in thermal contact with one or more resistive film coatings. A coating extends along the length of the grating and its local resistance varies along the length of the grating. In one embodiment, a plurality of overlaping coatings are chosen so the resistance variation of each is different, thereby permitting a variety of heat generation profiles to be effected by independent control of the coatings. The different heat generation profiles, in turn, proportionately change the grating geometric spacing and local refractive index along the grating length, providing the desired adjustable optical spacing profile. Other embodiments use resistive films with abruptly changing or periodically changing heating variation.

Abstract: In accordance with the invention, an optical waveguide comprising a longitudinally extending core housing an optical grating and a cladding layer peripherally surrounding the core, is provided with an outer surface of the cladding layer having one or more perturbations. Each perturbation has a height with respect to the core that varies by at least 0.1 times a Bragg wavelength of the grating over the surface of the perturbation and covers an extent of the outer surface whose linear dimensions are less than 1 cm. The perturbations suppress cladding mode spectra and reduce short wavelength cladding mode loss.

Abstract: A unique waveguide structure is provided in which the waveguide contains individual scattering elements that are capable of being tuned to provide local refractive index variations, e.g., on a micron scale—which is on the order of wavelengths typically used for communication system. According to the invention, the waveguide contains a core region, a cladding region, and a solid or liquid material having the tunable scattering elements dispersed therein, where the material is disposed within the core and/or cladding regions, and/or on the exterior of the cladding region. Useful scattering elements include, for example, liquid crystals dispersed in a polymer (polymer-dispersed liquid crystals—PDLC) or electrophoretic particles dispersed in a liquid medium.

Abstract: In accordance with the invention, an optical communication system is provided with one or more automatic dispersion compensation modules. Each module has an adjustable dispersion element, a data integrity monitor and a feedback network whereby the monitor adjusts the dispersion element to optimize system performance. In a preferred embodiment the dispersion compensating modules comprise chirped fiber Bragg gratings in which the chirp is induced in the grating by passing a current along distributed thin film heaters deposited along the length of the fiber. The magnitude of the applied current determines the dispersion of the grating. A data integrity monitor is configured to sense the integrity of transmitted data and to provide electrical feedback for controlling the current applied to the grating.

Abstract: This invention is predicated upon applicants' discovery that the performance of thermally adjustable fiber grating devices is enhanced by disposing them within a vessel for thermal isolation. The vessel is sufficiently larger than the fiber to avoid contact with the grating yet sufficiently small to isolate the grating from substantial air currents. Conveniently, the vessel is a cylindrical tube having elastomeric end seals. Advantageously microcapillary tubes passing through the elastomeric seals provide openings for the fiber to pass through the tube.

Abstract: A high speed optical communication system (≧10 Gbit/s) is compensated for temperature variation by providing it with one or more automatic dispersion compensation modules. Each module has an adjustable dispersion element, a data integrity monitor and a feedback network whereby the monitor adjusts the dispersion element to compensate for temperature variation. In a preferred embodiment the dispersion compensating modules comprise chirped fiber Bragg gratings in which the chirp is induced in the grating by passing a current along distributed thin film heaters deposited along the length of the fiber. The magnitude of the applied current determines the dispersion of the grating. A data integrity monitor is configured to sense the integrity of transmitted data and to provide electrical feedback for controlling the current applied to the grating.

Abstract: In accordance with the invention, an optical fiber is provided with a metal coating of controlled variable thickness by the steps of disposing the fiber in position for receiving coating metal from a metal source, and depositing metal while moving a shadow mask between the fiber and the source to provide patterning of deposited metal. Advantageously, the mask is translated at a constant velocity perpendicular to the fiber. The method is particularly useful for the fabrication of adjustable Bragg gratings.

Abstract: In accordance with the invention, an optical fiber grating device is made by providing a fiber with an electrically actuable component optically responsive to voltage or current and a plurality of conductive elements to locally activate the component and thereby to produce local optical perturbations in the fiber. In a preferred embodiment, a fiber is provided with a core of liquid crystal material and a plurality of periodically spaced microelectrode pairs. Application of a voltage to the microelectrodes results in a periodic sequence of perturbations in the core index which produces a grating. When the voltage is switched off, the grating switches off. Other embodiments utilize helical conductive elements.

Abstract: In accordance with the invention, an optical waveguide grating with adjustable chirp comprises a waveguide grating in thermal contact with an electrically controllable heat-transducing body which varies the temperature along the length of the grating. The heat-transducing body can generate heat on the fiber or remove heat from the fiber to establish a temperature gradient along the grating. In an exemplary embodiment, the heat-transducing body is a resistive film coating whose local resistance varies along the length of the grating. Electrical current passed through the film generates a temperature gradient along the grating approximately proportional to the local resistance of the film, and the amount of chirp can be adjusted by the current. The resulting devices are simple, compact and power efficient.

Abstract: In an optical fiber communication system a pulse reshaper can transform a distorted input light pulse into a reshaped output light pulse. The disclosed pulse reshaper is an all-optical pulse reshaper that comprises an optical waveguide having an effective length, the waveguide connecting the input and the output and comprising optical non-linear material, with a periodic variation of an effective refractive index of the optical waveguide. The optically non-linear material and the periodic variation are selected such that the reshaped output light pulse is a substantially transform-limited output light pulse.

Abstract: In accordance with the invention, an electrically modifiable optical fiber grating device is made by providing a fiber including a grating and forming a plurality of electrically conductive elements along the grating. In response to an electrical signal, the conductive elements modify the grating. In a preferred embodiment, a fiber grating is provided with a plurality of heating elements spaced to selectively heat different portions of the grating. This chirps the spacing between elements of the grating and thereby increases the bandwidth of the device.

Abstract: A tunable chromatic dispersion compensator for optical communication systems is disclosed. An optical grating, such as a fiber Bragg grating, non-chirped, linearly chirped or non-linearly chirped, is coated on its outer surface with a coating have a variable diameter and strained is applied to the fiber. The fiber may be latchably strained so that the grating characteristics may be changed or tuned while avoiding use of a continuous power supply. Various optical networking applications using such dispersion compensating devices are also disclosed.