At&t Bell Laboratories

At+t Corp.

Lucent Technologies Inc.

Norman A Whitaker, Jr

Alan Huang

Hercules Avramopoulos

M Christina Gabriel

Peter David Magill

Chia-Chang Li

Kotikalapudi Sriram

James E Dail

Henry H Houh

Paul M William French

STM traffic, e.g. voice and video telephony (VT), as well as packet mode (e.g. ATM) traffic, e.g. broadcast digital video, interactive television, and data, are transmitted via a multiple access broadband fiber/coaxial cable network. Customer premises equipment (CPE) at stations, and a bandwidth controller, which may be at a head end or central office, with which all stations communicate, work together to adapt to the changing demands of the traffic mix, and efficiently allocate bandwidth to a variety of bursty and isochronous traffic sources. The bandwidth allocation defines two types of time slots, STM and ATM, and divides each frame into two corresponding STM and ATM regions. The boundary between the regions can be changed dynamically. A contention access signaling channel is provided in the STM region, for call control and set-up requests. Within the STM region, the time slots can be of variable length and be allocated on a per call basis; the length of the time slots is proportional to the bandwidth requirement of STM calls. Within the ATM region, the time slots are of fixed length, each capable of accommodating one ATM cell. Further, the fixed length ATM time slots may be reserved for a particular user for the duration of a call, or may be shared through a contention process. At least one contention ATM time slot is always made available for signaling messages related to ATM call control and set-up requests. The downstream time frame is structured in a similar manner, but includes an additional MAP field to transmit to the stations ATM time slot allocation and status information for time slots in the upstream channel.

Method and apparatus enabling synchronous transfer mode and packet mode

A Sagnac gate-based self-routing optical signal switching node demultiplexes each channel of data bits of an N channel multiplexed optical data signal to one of a plurality of output terminals in accordance with the routing bit(s) of each data channel received in the N channel multiplexed optical data signal. In one embodiment, each data channel includes multiple routing bits enabling greater demultiplexer selectivity.

Self-routing optical communication node using Sagnac gates

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 crossbar exchange arrangement is implemented using a modified Sagnac switch. During the absence of a control signal, two separately numbered inputs are coupled to the same numbered outputs of the Sagnac switch (i.e., input1 to output1, etc.). During the presence of a control signal each of the two numbered inputs are switched and are coupled to a different numbered output (e.g., input1 to output2, etc.).

Optical crossbar exchange arrangement

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.

Low distortion all-optical threshold device

An optical switch employs a modified sagnac arrangement that includes a sagnac loop and a coupler for injecting a signal into the loop and developing thereby two signals that travel along the loop in opposite directions. The coupler has at least one signal port that is accessible from outside the switch. In addition, a coupler is included to inject a pump signal into the loop to travel through the loop only in one direction. The loop is made of, or comprises, a material that has a controllable propagation speed. More particularly, the propagation speed in the material is a function of, for example, the intensity of the pump signal. The switch action is attained when the applied signals are in the form of pulses with pulse widths and relative positions are controlled to achieve a particular interaction. The switch action is observed by sending a pulse down a sagnac loop and observing its return. Switching is activated by either sending or not sending a pump pulse concurrently with the signal pulse that is sent down the sagnac loop. When a pump pulse is sent, it is timed to orient itself so that the pulse that propagates faster through the loop precedes the pulse that propagates slower. While propagating through the loop, the faster pulse overtakes and surpasses the slower pulse, causing the two pulses to transverse each other. In this manner the pump pulse affects the propagation speed of the pulse sent through the sagnac loop and modifies the phase of the affected pulse as it re-enters the sagnac coupler. When the intensity of the pump pulse is properly controlled, the phase shift caused by the pump pulse is such that no output appears at the port of the sagnac arrangement.

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Atlantic Highlands, NJ, United States of America

Norman A Whitaker, Jr