At&t Bell Laboratories

At+t Corp.

Hercules Avramopoulos

Norman A Whitaker, Jr

Alan Huang

M Christina Gabriel

Paul M William French

An optical regenerator includes a clock recovery circuit which recovers an optical clock signal from a received deteriorated optical data signal. The recovered optical clock signal is used to generate a new optical clock signal. The new optical clock signal and the received deteriorated optical data signal are applied as an input signal and control signal, respectively, to a Sagnac switch which encodes the new optical clock signal with the encoded information of the deteriorated optical data signal thereby regenerating a clean optical data signal.

Optical regeneration circuit

An optical linear feedback shift register arrangement includes an optical encoding means implemented using a modified Sagnac switch. The encoding means encodes a received optical clock signal with a value derived from an exclusive-or of a first and second delayed version of an encoded signal received, respectively, at a first and second control ports. The resulting encoded clock signal, appearing at an output port, is then coupled through a first delay means to said first control port and coupled through a second delay means to said second control port. In another arrangement, an optical communication system utilizes the above-described linear feedback shift register to encode a data signal at a transmitter location and uses an identical linear feedback shift register at the receiver location to decode the encoded data signal.

Optical linear feedback shift register

An all-optical circulating shift register encodes a received optical clock signal with a value derived from an encoded optical signal received at a control port thereof. A data input to the shift register is used to modify an encoded optical signal. The resulting encoded clock signal, appearing at an output port, is coupled back to the control port. The shift register uses the encoded clock signal at the control port to encode a subsequently-received clock signal. In one embodiment, the optical shift register is implemented using a Sagnac switch having a feedback path coupled between an output port and a control port of the Sagnac switch.

Optical circulating shift register

Transmission capabilities of optical fibers are enhanced with all-optical means for removing noise from signal pulses and for creating clean output pulses with specified characteristics. This is accomplished with a nonlinear interferometer that is designed to operate on an amplified optical signal in the manner of a threshold device. More specifically, the nonlinear interferometer is designed to have a relatively level region in its input/output transfer function in the neighborhood of the low input signal and in the neighborhood of the high input signal. Depending on the input signal characteristics, it is sometimes beneficial to design the interfereometer so that the nominal high level of the input signal falls approximately in the middle of its corresponding flat region. In another embodiment, a bandpass filter is included at the output of the interferometer to remove the excess bandwidth that is created by the preceding amplifiers and the interferometer itself. The filter also removes the out-of-band noise in the input signal.

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Red Bank, NJ, United States of America

Hercules Avramopoulos