At+t Corp.

At&t Bell Laboratories

Lucent Technologies Inc.

American Telephone & Telegraph Co., At&t Bell Laboratories

At&t Intellectual Property I, L.p.

Bell Telephone Laboratories

Other

At&t Ipm Corp.

Bernard Glance

Robert W Wilson

Christopher Richard Doerr

Ivan P Kaminow

Kang-Yih Liou

Paul Shala Henry

Alfred Yi Cho

Mark John Karol

Martin Zirngibl

Clinton R Giles

Martin V Schneider

Lawrence Joel Greenstein

Daniel Lubzens

An optical ring network architecture including a number (N) of multi-add/drop filters, such as filters formed using pairs of frequency routers. Each multi-add/drop filter is coupled to two other multi-add/drop filters using N-2 transmission media, such as optical fibers, to form a ring. The network includes a number (N) of terminal stations associated with the multi-add/drop filters. A terminal station (p) is coupled with, and receives information from, its associated multi-add/drop filter (p) through a single optical fiber. The terminal station p is coupled with, and transmits information in a first direction around the ring to, a multi-add/drop filter p+1 through a single optical fiber. Communications from terminal station p to each other terminal station in the first direction are assigned one of N-1 wavelengths where no two wavelengths on a given optical fiber are associated with communications between terminal stations in the same direction.

Optical ring network architecture

An optical ring network architecture including a number (N) of multi-add/drop filters, such as filters formed using symmetrical pairs of frequency routers. Each multi-add/drop filter is coupled to two other multi-add/drop filters. using N&#x2212;2 transmission media, such as optical fibers, to form a ring. The network also includes a number (N) of terminal stations associated with the multi-add/drop filters. A terminal station (p) is coupled with, and receives information from, its associated multi-add/drop filter (p) through a single optical fiber. In addition, the terminal station p is coupled with, and transmits information in a first direction around the ring to, a multi-add/drop filter p+1 through a single optical fiber. Communications from terminal station p to each other terminal station in the first direction are assigned one of N&#x2212;1 wavelengths such that no two wavelengths on a given optical fiber are associated with communications between terminal stations in the same direction. Moreover, all wavelengths on a given optical fiber may be associated with a communication between terminal stations in either the first or second direction. As a result, each terminal station can communicate with each other terminal station simultaneously using wavelength division multiplexing and N&#x2212;1 wavelengths. The network may also be bi-directional such that each terminal station p is coupled with, and transmits information in a second direction opposite the first direction to, a multi-add/drop filter p&#x2212;1 through a single optical fiber.

An optical ring network architecture including a number (N) of multi-add/drop filters, such as filters formed using symmetrical pairs of frequency routers. Each multi-add/drop filter is coupled to two other multi-add/drop filters using N&#x2212;2 transmission media, such as optical fibers, to form a ring. The network also includes a number (N) of terminal stations associated with the multi-add/drop filters. A terminal station (p) is coupled with, and receives information from, its associated multi-add/drop filter (p) through a single optical fiber. In addition, the terminal station p is coupled with, and transmits information in a first direction around the ring to, a multi-add/drop filter p+1 through a single optical fiber. Communications from terminal station p to each other terminal station in the first direction are assigned one of N&#x2212;1 wavelengths such that no two wavelengths on a given optical fiber are associated with communications between terminal stations in the same direction. Moreover, all wavelengths on a given optical fiber may be associated with a communication between terminal stations in either the first or second direction. As a result, each terminal station can communicate with each other terminal station simultaneously using wavelength division multiplexing and N&#x2212;1 wavelengths. The network may also be bi-directional such that each terminal station p is coupled with, and transmits information in a second direction opposite the first direction to, a multi-add/drop filter p&#x2212;1 through a single optical fiber.

An optical ring network architecture including a number (N) of multi-add/drop filters, such as filters formed using symmetrical pairs of frequency routers. Each multi-add/drop filter is coupled to two other multi-add/drop filters using N&minus;2 transmission media, such as optical fibers, to form a ring. The network also includes a number (N) of terminal stations associated with the multi-add/drop filters. A terminal station (p) is coupled with, and receives information from, its associated multi-add/drop filter (p) through a single optical fiber. In addition, the terminal station p is coupled with, and transmits information in a first direction around the ring to, a multi-add/drop filter p&plus;1 through a single optical fiber. Communications from terminal station p to each other terminal station in the first direction are assigned one of N&minus;1 wavelengths such that no two wavelengths on a given optical fiber are associated with communications between terminal stations in the same direction. Moreover, all wavelengths on a given optical fiber may be associated with a communication between terminal stations in either the first or second direction. As a result, each terminal station can communicate with each other terminal station simultaneously using wavelength division multiplexing and N&minus;1 wavelengths. The network may also be bi-directional such that each terminal station p is coupled with, and transmits information in a second direction opposite the first direction to, a multi-add/drop filter p&minus;1 through a single optical fiber.

An inexpensive and efficient tunable electromagnetic filter is disclosed, having a wide range of tunable frequencies, comprising a holder with a number of filters mounted on the holder. The frequency of the filter is altered by moving the holder relative to a beam striking the holder so that one of the filters is filtering the beam. The frequency to be filtered may be easily and quickly changed, without altering the structure of the filter. In one embodiment the tunable filter is a disk rotatable by a motor with a number of fixed frequency filters mounted around the periphery of the disk. The filter is surrounded by four fibers providing and receiving beams, as with known add-drop filters.

Tunable add/drop filter

An apparatus and a method for laser frequency stabilization include a laser, a modulator, a derivative module, a Fabry-Perot etalon, a photodetector, a balanced mixer, a signal processing module, and a feedback control module. The laser has an output and lases at a single frequency. The laser has a desired frequency and provides an optical signal including a substantial frequency chirp signal. The modulator is coupled to the laser and provides a modulation signal for modulating the laser. The derivative module is coupled to the modulator and provides a derivative signal which is a time derivative of the modulation signal. The Fabry-Perot etalon is coupled to the output of the laser and has a frequency response including a plurality of resonances. One of the plurality of resonances is centered on the desired frequency. The etalon filters the optical signal according to the frequency response. The photodetector is coupled to the etalon and receives the filtered optical signal and provides a photocurrent in response to the filtered optical signal. The balanced mixer is coupled to the photodetector and to the derivative module. The balanced mixer provides a mixed signal by mixing the photocurrent with the derivative signal. The signal processing module is coupled to the balanced mixer and provides an error signal which is a time average of the mixed signal. The feedback control module is couple to the signal processing module and the laser. The feedback control module uses the error signal in order to adjust the single frequency of the laser.

Laser frequency stabilization apparatus

The present invention provides for a method and an apparatus for a single-frequency laser. The laser is in a Fabry-Perot configuration. An approximately V-shaped groove is etched through a top cladding layer, an active layer and, at least partially, a bottom cladding layer. A Fabry-Perot filter is deposited on top of the approximately V-shaped groove. A regrowth region is grown, at least in part, on top of the Fabry-Perot filter. The slope of the V-shaped Fabry-Perot filter and the thickness of the layers of the Fabry-Perot filter determine which mode of the Fabry-Perot configuration is transmitted through the Fabry-Perot filter and permitted to lase.

Method and apparatus for a single-frequency laser

A method and apparatus for realizing an optical multiplexer/demultiplexer having a continuous interferometer filter with a single &lgr;/2 dielectric layer is presented. The continuous interferometer filter is attached to a transparent substrate. One face of the substrate is tilted relative to the opposite face by a small wedge angle &ldquo;&dgr;&Oslash;&prime;&rdquo;. As a result of the small wedge angle &ldquo;&dgr;&Oslash;&prime;&rdquo; between the faces of the substrate, when a beam of light, composed of differing wavelengths, is introduced into the substrate at an incident angle &ldquo;&thgr;&prime;&rdquo; the beam zig-zags between the faces of the substrate at an increasing angle to the incident angle &ldquo;&thgr;&prime;&rdquo; proportional to the wedge angle &ldquo;67 &Oslash;&prime;&rdquo;. Accordingly, as the beam of light reaches the continuous interferometer filter at a different angle from the incident angle at each point, the filter passes through a wavelength corresponding to that new differing angle.

Method and apparatus for realizing an optical multiplexer/demultiplexer

A tunable wavelength selection device has two input ports and two output ports for receiving multiple wavelength channels at each input port and selectively outputting any desired combination of input wavelength channels at the two output ports. Wavelength channels are selected for output at a desired port by filtering and redirecting passed wavelength channels to again pass through the filter, or preventing wavelength channels from being incident on a filter. In exemplary embodiments, at least two filters are disposed between the input and output ports. At least one optical device is associated with at least one of the filters. The optical device selectably directs light that passes through the associated filter back through the associated filter, thereby selecting the wavelength channels for output at the output ports.

Tunable optical routing device and method

A tunable wavelength converter generates a selectable wavelength for an optical signal. The tunable wavelength converter includes an input active section, an output active section, an interferometer and an optical wavelength selector. The above components are integrated on a substrate between two mirrors. An optical input signal at a first wavelength is input through the input active section which in conjunction with the output section and the interferometer controls the amplitude of an optical signal at a second wavelength propagating in the laser cavity. The information contained in the amplitude of the input signal is transferred to the optical signal in the interferomic laser cavity and output by the output active section. Thus, the information of the optical input signal at the first wavelength is transferred to the optical output signal at the second wavelength.

Tunable wavelength converter

A parallel ring network is restorable upon sensing a failure of a transmission media. A central transmitter is coupled to one end of a first transmission medium. A central receiver is coupled to one end of a second transmission medium. A central sensor senses a transmission media failure centrally and provides a central alarm. In response to the central alarm, the central receiver is coupled to another end of the first transmission medium and the central transmitter is coupled to another end of the second transmission medium. At least one local station has a local receiver, a local transmitter, a local sensor for sensing a transmission media failure locally and providing a local alarm, and a local switch. In response to the local alarm, the local switch moves from a first position to a second position. When the local switch is in the first position, the local transmitter is coupled to the second transmission medium and the local receiver is coupled to the first transmission medium. When the local switching means is in the second position, the local transmitter is coupled to the first transmission medium and the local receiver is coupled to the second transmission medium. A method for restoring the parallel ring network is described.

Optically restorable WDM ring network using simple add/drop circuitry

A Wavelength Division Multiplexing (WDM) transceiver includes a Wavelength Multiplexer/Demultiplexer (WM/D) having a plurality of inputs (N) and N Amplified Light Emitting (ALED) devices, each ALED device transmitting a wideband optical signal to and receiving an optical signal from a different one of the N inputs of the WM/D transceiver. During transmission, the WM/D selects different wavelengths from ALED signals at each of the N inputs and multiplexes them together into a combined signal at its output. During receiving, the WM/D demultiplexes different wavelengths from a signal received at its output and sends the different wavelengths to each of the N inputs. A WDM system is formed using two WDM transceivers which are connected over an optical link and which alternately transmit and receive signals.

Full-duplex wavelength division multiplexing system using single-device

A selected positive coefficient resistor is connected in parallel across a laser, Light Emitting Diode (LED) or amplifier LED (ALED) to adjust the bias current, respectively, to the laser, LED or ALED as a function of temperature so as to maintain a more regulated optical power output therefrom.

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Colts Neck, NJ, United States of America

Bernard Glance