Abstract: Telecommunications switches are presented, including expandable optical switches that allow for a switch of N inputs×M outputs to be expanded arbitrarily to a new number of N inputs and/or a new number of M outputs. Switches having internal switch blocks controlling signal bypass lines are also provided, with these switches being useful for the expandable switches.

Abstract: Components of an optical communications network are described at a node of the network providing switching from one or more degrees of received optical signal routed to a plurality of receivers. The switch at the node generally includes a passive reconfigurable optical add drop multiplexer (ROADM) having drop or output ports that connector to optical channels leading to optical receivers without optical amplifiers between the ROADM outputs and the receivers. Configurations of the node and corresponding parameters are described that provide for use of lower cost components due to the absence of an array of optical amplifiers connected to the ROADM outputs.

Abstract: Telecommunications switches are presented, including expandable optical switches that allow for a switch of N inputs×M outputs to be expanded arbitrarily to a new number of N inputs and/or a new number of M outputs. Switches having internal switch blocks controlling signal bypass lines are also provided, with these switches being useful for the expandable switches.

Abstract: Telecommunications switches are presented, including expandable optical switches that allow for a switch of N inputs×M outputs to be expanded arbitrarily to a new number of N inputs and/or a new number of M outputs. Switches having internal switch blocks controlling signal bypass lines are also provided, with these switches being useful for the expandable switches.

Abstract: Telecommunications switches are presented, including expandable optical switches that allow for a switch of N inputs×M outputs to be expanded arbitrarily to a new number of N inputs and/or a new number of M outputs. Switches having internal switch blocks controlling signal bypass lines are also provided, with these switches being useful for the expandable switches.

Abstract: Telecommunications switches are presented, including expandable optical switches that allow for a switch of N inputs×M outputs to be expanded arbitrarily to a new number of N inputs and/or a new number of M outputs. Switches having internal switch blocks controlling signal bypass lines are also provided, with these switches being useful for the expandable switches.

Abstract: An all optical network for optical signal traffic provides at least a first ring with at least a first clockwise fiber, a second counter-clockwise fiber and a plurality of network nodes. Each node has at least a WDM transponder that with a line-side transmitter and a client-side receiver in a first direction, and a line-side receiver and a client-side transmitter in an opposing second direction. The line-side receiver includes a fixed or a tunable optical wavelength filter. At least a first add and a first drop broadband couplers are positioned on each fiber. Each coupler has first and second ports for through traffic and a third port for adding or dropping local traffic. The first add and first drop broadband couplers are configured to minimize a pass-through loss in each fiber. If there are multiple WDM transponders, their wavelengths are added to the ring either in series or in parallel. All wavelengths dropped from the ring are selected by each individual WDM transponder in a parallel or serial manner.

Abstract: Techniques and apparatus for optical communication networks including fiber ring networks with protection switching to maintain optical communications when an optical failure occurs and to automatically revert to normal operation when the optical failure is corrected. Implementations include use of a circulating optical probe signal at an optical probe wavelength within the gain spectral range of optical amplifiers used in a fiber ring network to detect an optical failure.

Abstract: An optical carrier notch filter includes an optical coupler with at least first, second and third ports. The first port is configured to receive an output that includes an optical carrier and interleaved optical single sideband signals. An optical bandpass filter is coupled to a port of the optical coupler. The optical bandpass filter separates the output into a transmitted signal that contains the optical carrier, and a reflected signal that includes the interleaved optical single sideband signals. The reflected signal is reflected from the optical bandpass filter to the third port of the optical coupler.

Abstract: Optical communication networks having multiple interconnected optical rings and optical protection switching mechanism to reduce communication delays and improve optical signal-to-noise ratios. Optical ring networks using variable optical attenuators for protection switching are also described.

Abstract: An all optical network for optical signal traffic provides at least a first ring with at least a first clockwise fiber, a second counter-clockwise fiber and a plurality of network nodes. Each node has at least a WDM transponder that with a line-side transmitter and a client-side receiver in a first direction, and a line-side receiver and a client-side transmitter in an opposing second direction. The line-side receiver includes a fixed or a tunable optical wavelength filter. At least a first add and a first drop broadband couplers are positioned on each fiber. Each coupler has first and second ports for through traffic and a third port for adding or dropping local traffic. The first add and first drop broadband couplers are configured to minimize a pass-through loss in each fiber. If there are multiple WDM transponders, their wavelengths are added to the ring either in series or in parallel. All wavelengths dropped from the ring are selected by each individual WDM transponder in a parallel or serial manner.

Abstract: An all optical network for optical signal traffic has at least a first ring with at least one transmitter and one receiver. The first ring includes a plurality of network nodes. At least a first add/drop broadband coupler is coupled to the first ring. The broadband coupler includes an add port and a drop port to add and drop wavelengths to and or from the first ring, a pass-through direction and an add/drop direction. The first add/drop broadband coupler is configured to minimize a pass-through loss in the first ring and is positioned on the first ring.

Abstract: An all optical network for optical signal traffic has at least a first ring with at least one transmitter and one receiver. The first ring includes a plurality of network nodes. At least a first add/drop broadband coupler is coupled to the first ring. The broadband coupler includes an add port and a drop port to add and drop wavelengths to and or from the first ring, a pass-through direction and an add/drop direction. The first add/drop broadband coupler is configured to minimize a pass-through loss in the first ring and is positioned on the first ring.

Abstract: An all-optical label swapping system and method superimposes a low-speed ASK label on top of a high-speed DC-balanced-line-coded ASK payload. An old ASK label is erased by modulating the combined payload and label signal with the inverse of the received ASK label. This ASK labeling technique requires only low speed external modulators and low speed optical receivers to perform the label swapping mechanism, and does not require sophisticated optical components.

Abstract: An optical carrier notch filter includes an optical coupler with at least first, second and third ports. The first port is configured to receive an output that includes an optical carrier and interleaved optical single sideband signals. An optical bandpass filter is coupled to a port of the optical coupler. The optical bandpass filter separates the output into a transmitted signal that contains the optical carrier, and a reflected signal that includes the interleaved optical single sideband signals. The reflected signal is reflected from the optical bandpass filter to the third port of the optical coupler.

Abstract: A method and device for wavelength conversion, wavelength buffering and label/header swapping. A wavelength buffer is used to provide for in-band wavelength conversion in, for example, a dense wavelength division multiplexing communications system. The same device may be used for label/header swapping without wavelength conversion.

Abstract: A method and device for wavelength conversion, wavelength buffering and label/header swapping. A wavelength buffer is used to provide for in-band wavelength conversion in, for example, a dense wavelength division multiplexing communications system. The same device may be used for label/header swapping without wavelength conversion.

Abstract: An optical carrier notch filter includes an optical coupler with at least first, second and third ports. The first port is configured to receive an output that includes an optical carrier and interleaved optical single sideband signals. An optical bandpass filter is coupled to a port of the optical coupler. The optical bandpass filter separates the output into a transmitted signal that contains the optical carrier, and a reflected signal that includes the interleaved optical single sideband signals. The reflected signal is reflected from the optical bandpass filter to the third port of the optical coupler.

Abstract: Optical techniques, devices and systems for combining duobinary modulation and optical subcarrier multiplexing in optical communication applications. An analog mixer is used to mix a duobinary signal for a data channel and a local oscillator signal to produce a modulation control signal for controlling the subsequent optical subcarrier multiplexing modulation. Various optical subcarrier multiplexing modulation techniques may be used including optical single sideband modulators and optical double sideband modulators.

Abstract: This application describes, among others, fiber ring networks with two fiber rings to provide local fiber failure protection in each node and capability for each node to broadcast to other nodes, and to establish uni-directional and bi-directional communications with one or more selected nodes. Each optical channel may have a single optical break point in the ring networks and this single optical break point is located in a designated node. Various application may advantageously use such ring networks such as ring networks with asymmetric traffic like video-on-demand systems and other information systems.