At&t Bell Laboratories

At+t Corp.

Mario A Santoro

Kai Y Eng

Zygmunt Haas

Richard Dennis Gitlin

Mark John Karol

Jack Harriman Winters

Craig D Poole

The capacity of a multi-mode optical fiber system, such as a local area network, is increased by selectively propagating only higher-order modes through the multi-mode fiber. Because only a small number of higher-order modes are propagated, pulse spreading induced by modal dispersion is minimized, and the bandwidth of the multi-mode fiber is increased. Because of the reduced modal dispersion, higher-order modes are recovered from the multi-mode fiber in accordance with the invention without filtering the output of the fiber. This renders the system less vulnerable to mechanical perturbations that are known to reduce the bit error rate of systems requiring filtering. Thus, by propagating only higher-order modes in this manner, the 'bandwidth-distance' product of the multi-mode fiber is significantly increased.

Lightwave transmission system using selected optical modes

The polarization-dependent distortion of an optical signal transmitted through an optical fiber is reduced by aligning the polarization of the optical signal to minimize the received signal distortion. A polarization controller (a device which can change the polarization of light in an optical fiber) may be located at either the input or output end of a long haul optical fiber system and is used to align the polarization of the signal to minimize the received signal distortion. Automatic operation of the polarization controller can be obtained by using a steepest-descent method based on a distortion measure of the received signal for the optical signal transmitted through the optical fiber to generate control signals which are used to control the polarization controller.

Fiber-optic transmission polarization-dependent distortion compensation

A plurality of M receivers are utilized to receive a plurality of N channels from various incoming multiplexed data signals, N.gtoreq.M, where each incoming data signal arrives on a separate wavelength and comprises several channels. Each of the M receivers, in sequence, receives a separate one of the N channels, thereby M of the N channels. The process then repeats for the next M channels, in the same sequence as the first M channels. The repetitions continue until all N channels are received.

Interleaved receivers

An interconnect fabric is constructed from a plurality of fixed wavelength transmitters which are used to transmit arriving data packets through a star coupler, and a plurality of tunable receivers which tune to whatever frequency necessary to receive the desired data from the star coupler. A control network, constructed from a plurality of fixed wavelength receivers and a plurality of tunable transmitters, determines what frequencies the tunable receivers should tune to, and sends a signal to effectuate such tuning.

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Shrewsbury, NJ, United States of America

Mario A Santoro