Mci Communications Corporation

Avanex Corporation

Worldcom, Inc.

Mci Worldcom, Inc.

Xiaoping Charles Mao

Guohua Xiao

Andrew Niall Robinson

Lintao Zhang

Xiaofan Cao

Glenn A Wellbrock

Simon X F Cao

Harold Clay Wispell, Ii

Viet Le

Joseph C Cook

A system and method for modular multiplexing and amplification of optical signals in subwindows within an operating window of a fiber optic communication network. An operating window is divided into subwindows. Optical signals in each subwindow are optically amplified separately and in parallel by a plurality of optical line amplifiers. According to one embodiment, the operating window is divided into four subwindows within an erbium wavelength band. Each subwindow corresponds to a different group of channels having optical signals of a different wavelength. Modular wavelength division multiplexing (WDM) units multiplex/demultiplex optical signals in the set of multiple channels. A modular WDM unit includes a coarse WDM unit and four fine WDM units. The coarse WDM multiplexes optical signals by wavelength into subwindows separated by relatively large guard bands. A fine WDM unit further multiplexes optical signals within a subwindow by wavelength into individual channels with a fine separation. Fine WDM units and optical line amplifiers can be added in a modular fashion, as needed, to support actual or anticipated traffic in the corresponding subwindows and channels therefor. Dispersion magnitude and slope can be managed across channels within subwindows without expensive equalization circuits. A multi-channel plan for high-speed WDM traffic in an erbium band can be adopted and installed in a modular fashion on existing single-mode fiber networks with less initial cost and more flexible design.

Method and system for modular multiplexing and amplification in a multi-channel plan

A self-adjusting optical add-drop multiplexer monitors the power in a drop signal and attenuates the power in an add signal to match the power in express WDM channels (signals). When used in a fiber network, and more particularly, in a metro network, the deleterious effects of optical amplification are reduced. Power attenuation is also used in an optical switching assembly particularly useful in two-fiber ring network. The optical switching assembly monitors drop channels from the two rings of the network and attenuates the add channel(s) accordingly. An optical switch operates to direct the drop signal from one of the two rings to a receiver in accordance with a control signal based on the monitored drop channels. The self-adjusting optical add-drop multiplexer also monitors the power in the drop signals and issues an alarm if the drop signal is of a power level above or below predetermined levels.

Self-adjusting optical add-drop multiplexer and optical networks using same

A fiber optic communications link having PMD characterization across multiple optical channels to identify PMD problems. The communications link has adaptive PMD controls employed along the optical link, whereby PMD phenomena detected by instruments, such as PMD compensators, are interpreted as being either attributable to perturbation of fiber characteristics at large, or by failure of PMD equipment along the link. The present invention avoids taking unnecessary control or maintenance actions upon PMD related controllers and compensators. PMD notifications from various PMD compensators are correlated to identify which portion of the link has undergone a change in polarization characteristics to further identify PMD related errors and problems.

PMD characterization across multiple optical channels of an optical link

A method and apparatus for managing state-of-polarization (SOP) controllers along an optical communications link. When the polarization-mode dispersion (PMD) in the link exceeds a preset limit as determined by a PMD compensator, the SOP controller is directed to change rotation angle in an arbitrary fashion. This shift is only undertaken after other indicators are examined to determine that PMD is the main problem affecting the link, and not simply a consequence of a separate problem that the SOP controller rotation angle should not try to fix. By reducing unnecessary SOP adjustments which can disrupt data traffic, the reliability of the optical link is improved.

Method of avoiding excessive polarization mode dispersion in an optical communications link

The present invention provides an improvement in the separation mechanism to be used in a dense wavelength division multiplexer. The separation mechanism in accordance with the present invention includes an asymmetric pass band interferometer. The interferometer includes a first glass plate optically coupled to a second glass plate, forming a space therebetween; a first reflective coating with a first reflectivity residing inside the space and on the first glass plate; a second reflective coating with a second reflectivity residing inside the space and on the second glass plate; a first waveplate with a first optical retardance residing inside the space; and a second waveplate with a second optical retardance, optically coupled to the first glass plate and residing outside the space, where a combination of values for the first reflectivity, the first optical retardance, and the second optical retardance effect a separation of channels in at least one optical signal into at least two sets, and where the at least two sets have asymmetrically interleaved pass bands. The asymmetric pass band interferometer in accordance with the present invention is capable of separating channels from signals with different data transfer rates. With the present invention, a maximum use of available bandwidth on an optical fiber may be accomplished. An added functionality of the asymmetric pass band interferometer of the present invention is the ability to facilitate an asymmetric or uneven add/drop function while also separating the channels.

Dense wavelength division multiplexer utilizing an asymmetric pass band interferometer

A bi-directional telemetry service channel is provided on a single optical fiber using two wavelengths that are accessible through multiplexing devices. A bi-directional telemetry service channel is also provided on a single optical fiber using only a single wavelength. A fully protected bi-directional telemetry service channel can be provided using only two optical fibers. When a single wavelength is used, a time window is provided for transmission of telemetry service signals in one direction on the optical fiber at the single wavelength, and a second time-window is provided for transmission of telemetry service signals in the opposite direction on the same optical fiber using the same wavelength.

System and method for bi-directional transmission of telemetry service

Dense wavelength division multiplexing within a 1310 nm band is accomplished over a single mode fiber. Carrier wavelengths are selected from within two windows, a low subband and/or a high subband, on either side of a guardband. The guardband includes the zero dispersion wavelength .lambda..sub.0 of a single-mode fiber in the optical communication link and separates low subband and high subband within the 1310 nm band. Dispersion compensation is provided for carrier signals in each dense WDM channel in the low and high subbands.

Dense WDM in the 1310 nm band

A system and method for optimizing the performance, in a multichannel optical transmission system, of an optical signal regenerator, by compensating for input signal power fluctuation and for output signal gain change, and by mildly filtering individual wavelengths between gain block stages. A system and method to provide amplification and refinement of a bidirectional optical signal in a single amplification and refinement stage.

Growing community of inventors

Plano, TX, United States of America

Xiaoping Charles Mao