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: Polarization monitoring and control in a lightwave communication system is achieved by using an in-line polarimeter in conjunction with a polarization controller. The devices are readily compact, accurate and therefore capable of implementation in a variety of system applications. In one embodiment, a polarimeter and controller can be coupled together by a feedback loop between the polarimeter output and the controller input to provide “active polarization control” (APC).

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 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: An in-line optical fiber polarimeter comprises a plurality of fiber gratings and a single wave plate, disposed sequentially along a length of optical fiber. The fiber gratings are precisely oriented and have a predetermined grating period such that each grating functions to out-couple a predetermined portion of the optical signal passing through the polarimeter. A separate detector is associated with each grating to measure the out-coupled signal. The four Stokes parameters can be determined from the set of measurements and then used to determine to state of polarization of an optical signal passing through the polarimeter.

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.

Abstract: A method for making a chirped grating device capable of a broad bandwith for optical communication systems is disclosed. An intrinsically-chirped optical grating is externally strained to alter the range of chirping. The external strain may be induced by a gradient-generating body bonded onto the length of the fiber grating that 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.

Abstract: A tunable chromatic dispersion compensator for optical communication systems is disclosed. An optical grating, such as a fiber Bragg grating, nonchirped, linearly chirped or non-linearly chirped, is strained to alter the dispersion compensator characteristics, preferably with a gradient-generating body bonded onto the length of the fiber grating. The body 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.

Abstract: L-band EDFA (Er-doped fiber amplifier) characteristics are improved by provision of filter means in the C-band, the filter means having a figure of merit greater than 400dB.multidot.nm. The filter means can be discrete and/or distributed filter means. In preferred embodiments, two or more full C-band blazed fiber Bragg, gratings are used.

Abstract: A dispersion compensating chirped optical fiber Bragg grating according to our invention is formed in polarization maintaining (PM) fiber having birefringence of at least 10.sup.-6, preferably 10.sup.-5 or more. Use of the PM fiber makes possible substantial cancellation of the polarization mode dispersion that typically is unavoidably present in chirped Bragg gratings for dispersion compensation.

Abstract: A programmable and latchable device for wavelength shifting and chromatic dispersion compensating is disclosed. An optical grating such as a Bragg grating, a nonchirped grating, or a linearly or non-linearly chirped grating, is magnetostrictively strained to alter the dispersion compensator characteristics. In a preferred embodiment, a gradient magnetostrictive body is bonded along its length to the fiber grating. In yet another preferred embodiment, a magnetostrictive body is bonded onto the length of the fiber grating, and a gradient generating, programmable and latchable magnet component is placed adjacent the magnetostrictive body. The body is then latchably strained to a desired level by controlling the extent of magnetization in the magnetostrictive material and the magnet so as to induce or enhance chirping characteristics in the grating. Various optical applications using such are disclosed.

Abstract: In accordance with the invention, a temperature-dependent rare earth doped waveguide optical amplifier is compensated by a temperature-dependent loss filter. The filter characteristics are designed to be temperature-dependent filters so that the gain characteristic of the amplifier is compensated over a practical operating temperature range. In essence, the amplifier comprises a length of optical waveguide for transmitting optical signals, a rare earth doped amplifying region in the waveguide for amplifying the transmitted optical signals, a pumping source for optically pumping the amplifying region, and a temperature-dependent loss filter. A typical design compensates an EFDA to a variation of less than 1 dB over a temperature range of -40.degree. C. to 85.degree. C. and a spectral range of at least 20 nm.