Abstract: The present invention provides a system, method and apparatus for maintaining a connection between a server and a client by receiving a message, determining whether to store one or more elements of the message, storing the one or more elements of the message when the one or more elements of the message are to be stored, transmitting the message, and determining whether the server has failed and when the server has failed, restoring the server to a pre-failure connection state using the one or more stored message elements.

Abstract: A photomultiplier module (PMT), preferably a PMT with a gallium arsenide (GaAs) photocathode, is used as a N-photon detector (N is an integer ?2). The PMT detects the N-photon absorption rate of an optical signal having a wavelength range extending from 1.0 ?m to an upper wavelength region that increases as the number of photons simultaneously absorbed by the PMT increases beyond two. The N-photon absorption rate is used by a signal compensation apparatus to reduce impairments which affect the rate, such as group velocity dispersion and/or polarization mode dispersion, in a received optical pulse communication signal. The N-photon absorption rate can also be used to determine the optical signal-to-noise ratio of a received optical pulse communication signal, and/or to synchronize a second optical pulse signal with the first optical signal.

Abstract: A method and apparatus for variable duty cycle generation of optical RZ data signals uses a single, NRZ-driven phase modulator followed by a optical delay-line interferometer. If desired, a differential encoder precodes an NRZ data signal before being applied to the data input of a phase modulator arranged to modulate the light emerging from a continuously operating laser. The output of the modulator is then applied to an optical delay interferometer, such that the optical signal is split into first and second optical signals, each of which is applied to a respective one of the two interferometer arms. The interferometer is arranged such that the signal in one of the arms is controllably delayed with respect to the other (a) by a fine delay (on the other of the optical wavelength) to produce destructive interference in the absence of phase modulation by said phase modulator, and (b) by a coarse delay (on the order of a bit period), to produce RZ pulses having the desired duty cycle.

Abstract: In a network of interconnected edge and core routers, where packet data flows are received at edge routers and then transmitted toward intended destinations via a path through one or more core routers, fair bandwidth sharing is achieved without per-flow state monitoring in the interior routers. Each edge router is arranged to divide each input data flow into a set of layers each having an associated level, based on rate. The division process is done without reference to the content of the flow, and can use layers of equal or unequal size. The packets in a flow are marked at an edge router with their layer level, in a globally consistent manner. Each core router maintains a layer level threshold, based upon buffer management conditions, and drops layers whose level exceeds the threshold. During congestion, the level threshold is decreased; when congestion clears, the level threshold is increased.

Abstract: A delayed interference all-optical wavelength converter is arranged to convert and reshape a pulsed input signal Pin at &lgr;1 into the wavelength converted signal Pconv at &lgr;2, where &lgr;1 and &lgr;2 are different. A delayed interference all-optical wavelength regenerator is similar, but is arranged to reshape a pulsed input signal Pin into the wavelength converted signal Pconv, where the wavelengths of the input signal and the converted signal are the same. The converter/regenerator comprises an input-signal coupling unit for receiving the pulsed input signal and supplying it to one input of a modulation section, the other input to which is a carrier signal Pcw. The output of the modulation section Pint, which is generally speaking, a phase modulated signal which may also have an amplitude modulated component, is applied to a delay interference section arranged to transform Pint into a primarily amplitude-modulated signal.

Abstract: An optical transmission system is provided which uses optical single-sideband (SSB) modulation and incorporates at least one mid-span analog SSB regenerator arranged to produce a phase conjugation of the transmitted signal. The phase conjugation technique, referred to here as complementary sideband regeneration (CSR), is accomplished on the retransmitted optical signal in the electrical domain, and requires no nonlinear optical techniques.

Abstract: An optical cross connect switch includes a programmable demultiplexer placed on every input transmission port, a programmable multiplexer placed on every output transmission port, and a linking fiber between every programmable demultiplexer and multiplexer in the system. The programmable demultiplexers and multiplexers handle internally all the optical communication channels, and can route any specified optical channel from an input port to the desired output port. Advantageously, the arrangement can send several input channels to the same output port, and can efficiently handle a large optical communication channel count, offer a scalable cost-effective solution for expanding switching capacity, and reduce the fiber interconnection count between switch modules.

Abstract: Optical chirped return-to-zero (CRZ) data signals are generated without the need for a separate phase modulator, by using a dual-drive Mach-Zehnder modulator for RZ pulse carving that is driven with two typically sinusoidal signals of either unequal amplitude or unequal relative phase, i.e. of non-vanishing phase difference.

Abstract: A thermo-optic interferometer switch is arranged to operate in a Push-pull mode by placing approximately a quarter-wavelength effective path-length difference (90 degree bias) between the arms of an interferometer switch in the zero-drive state, and then driving one arm to activate the switch to one state (e.g., the bar state), and driving the other arm to go to the other state (e.g. the cross state).

Abstract: A programmable optical demultiplexer can independently assign every input optical channel in a WDM optical communications signal to depart from any desired output port. The demultiplexer device can also be operated in the reverse direction, and thus achieve programmable optical multiplexer functionality, by accepting different wavelengths at each of multiple input ports and efficiently combining the wavelength channels at the multiplexer output port. The programmable multiplexer/demultiplexer device has an optical arrangement for spatially dispersing the optical wavelengths, and tunable micro-mirrors for beam steering each channel independently. Controlling the beam reflection direction determines the connectivity between the input and output ports at the wavelength level.

Abstract: A wavelength converter with a monolithically integrated delay loop in a delayed interference configuration that needs only one SOA or other non-linear optical element coupled to the input fiber, a first coupler arranged to split the output of the SOA or other non-linear optical amplifying element into two paths having controllable delay and phase shift characteristics, and at least one output coupler to combine the signals present on the two paths to provide the converter output. One embodiment of the invention has a monolithically integrated delay loop utilizing one or more asymmetric couplers. Another embodiment of the invention has a coupler that does not require an asymmetric splitting ratio, and has either a gain element in one of the paths, an attenuation element in one of the paths, or both.

Abstract: Traffic on a connectionless (CL) network, such as IP packets, can be routed onto a connection a connection oriented (CO) network, such as an ATM telephony network, when it is advantageous to do so from a user or service provider viewpoint, without affecting the ability of users to continue to use existing applications. Routing is controlled by nodes called CL-CO gateways, with connectivity to both the CL network and the Co network. When CL traffic originating at a source reached these gateway nodes, a decision is made whether to continue carrying the information in the CL mode, or to redirect the traffic to a CO network.

Abstract: A method and apparatus for producing a flat gain over very broad gain bands utilizing backward-pumped Raman amplification. The method allows for dynamic gain control through simple electronic means.

Abstract: The number of possible circuits that can be linked to each node operating in accordance with the IS-IS standard is expanded from the 256 limit set by the IS-IS standard to a larger arbitrary number. Each node is initially assigned and can use on each circuit a pseudonode ID containing any arbitrary, non-zero circuit ID. This status continues until it is determined that the said node is to become DIS on this LAN; if that happens, the arbitrary circuit ID is abandoned, and the system itself is allowed (using the IS-IS standard process) to reassign a pseudonode ID containing a circuit ID that is indeed unique on the LAN and therefore unused. If the said node has not been determined as DIS on the LAN, it continues to use the arbitrarily assigned circuit ID.

Abstract: The curvature, tilt, and attenuation of the passband of an optical signal is dynamically controlled by an integrated compensator that is advantageously electrically operated. The compensator arrangement can be replicated, and used to independently and dynamically control the passbands of multiple optical signals having different wavelengths, for example in a multiplexing and/or demultiplexing arrangement. Each compensator includes a “50/50” splitter arranged to divide an optical signal into first and second copies. One copy is applied to a first variable optical attenuator (VOA) via a tunable phase shifter, while the other copy is applied to a second VOA directly. The outputs of the first and second VOA's are then combined, for example in a planar waveguide grating. In the output on the other side of the grating, the two copies interfere.

Abstract: A Raman-amplified optical transmission system 80 includes a source of optical transmission signals having a system wavelength, &lgr;s, that are connected to one end of the of a first optical fiber 50-1 having a large effective area, i.e., Aeff≧70 &mgr;m2. The other end of the first optical fiber is connected to a second optical fiber 50-2 having a small effective area, i.e., Aeff≦60 &mgr;m2. Preferably, the first and second optical fibers have opposite dispersion signs. A wavelength-division multiplexer 87, for example, couples optical transmission signals &lgr;1 . . . &lgr;n, from an optical pump 88 to the second optical fiber that cause it to exhibit stimulated Raman scattering, which provides amplification of the optical transmission signals. Preferably, the optical pump signals propagate along the second optical fiber in a direction that is opposite the direction of the optical transmission signals. Exemplary cables 500, 600 are disclosed that include both large and small-effective-area fibers.

Abstract: A method and apparatus for overcoming modal noise penalties associated with multi-mode fiber optic links operating at high data rates on the order of 10 Gb/s. The method involves restricting the center launch condition of optical signals into the multi-mode fiber while permitting loose tolerances between source and fiber.

Abstract: A method for defining a call forward operation in a telecommunications system. A user activates a call forward function, and receives a system response proposing a default value for the orginator. The user either validates the default originator or makes and validates an alternate choice. Once the originator is validated, the user receives a system response proposing a default value for the destination. Once again, the user either validates the default destination, or makes and validates an alternate choice. The originator and destination are identified by the system by an assigned number, user name or combination of assigned number and user name.

Abstract: Multiple microcell base stations are located within a macrocell having single macrocell base station in an hierarchical architecture, and microcell users (&mgr;-users) and macrocell users (M-users) communicate respectively with the &mgr;-base and the M-base using the same frequency band, by appropriately (a) selecting the ratio of the radius r of each &mgr; cell and the average distance d from the M-base (r and d are measured by the “radio distance”, which includes the effects of shadowing), and (b) controlling the power level with which uplink (mobile to base) and downlink (base to mobile) messages are communicated. Typically, &mgr;-cell size and location are chosen such that d/r>10. With respect to uplink communications, the transmit powers of the &mgr;-users in a &mgr;-cell are controlled so that the total received power at the nearest M-base is equivalent to the received power from C M-users, where C is usually set to unity.

Abstract: A wavelength converter with a monolithically integrated delay loop in a delayed interference configuration that needs only one SOA, only one in and one output fiber. Unlike prior-art hybrid wavelength converters, our inventive device has a monolithically integrated delay loop utilizing an asymmetric splitting ratio.