Abstract: A method for determining optimal locations and values of dispersion compensating modules (DCMs) in an optical network is provided. The method comprises repeatedly evaluating possible combinations of DCM values and locations and adding to the combination having the lowest score until a solution of DCMs is formed that satisfies the dispersion limits of the network. This method provides an optimal solution with, for example, the lowest value of DCMs necessary to meet dispersion specifications. In one embodiment, the method for determining the optimal location and value of the DCMs uses a priority queue to store the different combinations of DCM values and locations. Modifications to the method include variations in the score function, for example to minimize the total cost of the DCMs. In another embodiment, a series of priority queues are used to improve the efficiency of the method by reducing the amount of processing required to sort the priority queues.

Abstract: Quake Transistor Logic (QTL) circuits of the embodiments of the invention are low power, high-speed circuits that can be manufactured by the same process as the lower-speed complex circuits, and are thus capable of being integrated on the same device. A number of techniques are employed to give QTL circuits their unique advantages. Lower power without loss of speed is achieved through the use of a self-biasing clock buffer to eliminate the need for tail current sources in the logic; differential signals are employed throughout to improve noise immunity with a low logic signal swing; an optional tuning circuit provides extension of the frequency response to achieve an even higher clock frequency and logic circuit bandwidth.

Abstract: A stacked backplane assembly, including two or more backplanes or midplanes having different functionality and combined together so as to form an integral unit, is provided. The backplanes forming the assembly are manufactured with prime and secondary manufacturing holes to enable alignment, so that the resulting tolerance build-up of the assembly is similar to that of a single backplane. Connectors can be arranged on the backplanes of the assembly so that an electronic or optical card can be simultaneously plugged in to one or more of the backplanes that comprise the stacked backplane assembly. The stacked backplane assembly of the embodiments of the invention is illustrated by having power and signal backplanes and midplanes, but can be equally applied to backplanes that provide other types of functionality.

Abstract: Methods and devices are provided for optical demultiplexing and optical multiplexing. An optical wavelength demultiplexer adapted to perform wavelength demultiplexing of an input optical signal containing a plurality of wavelengths is provided. A tuneable filter in combination with a device with a required free spectral range results in a tuneable demultiplexer arrangement which eliminates the need to inventory large numbers of different demultiplexers. Similarly, tuneable lasers in combination with a device with a required free spectral range result in a tuneable multiplexer arrangement.

Abstract: Various methods and apparatuses are provided for performing a radix-M FFT (Fast Fourier Transform) upon N time domain samples to produce N/S frequency domain samples for detecting tones of dithers impressed on channels of a WDM (wavelength Division Multiplexed) optical signal. Successive tones have a tone frequency spacing, &Dgr;fta, and a sampling frequency, fs, is chosen so that fs=N&Dgr;fta/S. S is a spacing given by S=Mw with w being an integer. The radix-M FFT is performed in k=logm(N) stages and within the stages a reduced number of radix-M computations, when compared to the number of radix-M computations of a conventional radix-M FFT, are performed on data points associated with the N time domain samples. This is possible because successive frequency domain samples of the N/S frequency domain samples differ by &Dgr;fta=S&Dgr;f where &Dgr;f is a frequency bandwidth.

Abstract: An optical connection arrangement is provided in an optical path to facilitate changing optical add/drop multiplexer (OADM) and other optical component modules while optical traffic is present on the optical path, with minimal interruption to such traffic. The connection arrangement has a plurality of optical ports to each of which an optical component can be coupled, and one or more optical switches which can be controlled to selectively include in the optical path or bypass each optical port. Such connection arrangements can be coupled in series and/or in parallel for convenient modular add/drop configurations and for opposite directions of transmission of optical traffic on respective optical paths.

Abstract: Provided is a signal detector and method for spectrum analysis and for measuring power of one or more channels of an electrical or optical signal. Each channel may carry a unique modulation tone. A DSP (digital-signal processor) performs DFTs (discrete Fourier transforms) on the signal. Frequency bands of interest which contain a tone that requires detection are processed. Higher layers of coherent integrations are performed on bands which have not detected a tone with a resolution that is suitable for power measurement. The higher layers of coherent integrations are performed by collecting additional data and performing a coherent integration. Further higher layer coherent integrations are performed until all modulation tones have been detected with a suitable resolution or up to a maximum detection latency.

Abstract: The invention describes an optical network architecture which uses a limited number of wavelength channels while providing flexible connections between the network nodes. Each node in the network deploys a fixed wavelength transmitter and a fixed wavelength receiver, whose wavelengths are misarranged so that a set of wavelengths of the transmitter differs from the set of wavelengths of the receiver, and wavelengths of transmitters and receivers at different nodes are arranged so that for any pair of nodes there is at least one common wavelength which is the same for one of the transmitter and receiver at one node and one of the respective receiver and transmitter at the other node, thus providing a direct connection between the nodes. The corresponding structure of the optical add/drop multiplexer/demultiplexer for use at the network node, and method of providing direct connections between the nodes, are also provided.

Abstract: An interconnection module for holding and interconnecting optoelectronic cards is provided. It includes an optical midplane which accommodates and flexibly interconnects N optoelectronic cards on one side of the midplane and M cards on the other side of the midplane. Optical connectors, which are arranged on the midplane and on the cards, provide arrangement of cards on the midplane in one of the two positions, in the first position the cards on opposite sides of the midplane being parallel to each other, and in the second position the cards being perpendicular to each other. Preferably, each of the N cards on one side is connected to a subset of cards on the other side, the number of cards in the subset being variable for each of the N cards and less or equal to M in total. Additionally, a backplane section of the module, having a plurality of connectors joined via laminated strands, may be added as an extension of the midplane to interconnect any required number of cards on same side of the midplane.

Abstract: A method of transmitting interleaved real-time and non-real-time data on a packet based network so as to provide voice Quality of Service comparable to the Time Division Multiplexing realm of traditional telephony. The method reduces packet jitter and delay by employing separate queues for the different types of data as well as through the use of jitter buffers. The interleaving method consists of a number of discrete concepts and mechanisms that when used together in the manner disclosed herein provides consistent high-quality transmission of real-time data over packet/frame/cell-based networks. The elements required for this method include time-slot co-ordination, a dynamic MTU algorithm, and a Multiple queue egress traffic management system.

Abstract: A method and device are provided for an improved system and method of labeling data units with a domain field that is fast, scalable and simple to implement in domain switching applications without adding to the protocol overhead. The system and method are also suitable for point-to-multipoint configurations.

Abstract: The invention describes an optical network architecture which uses a limited number of wavelength channels while providing flexible connections between the network nodes. Each node in the network deploys a fixed wavelength transmitter and a fixed wavelength receiver, whose wavelengths are misarranged so that a set of wavelengths of the transmitter differs from the set of wavelengths of the receiver, and wavelengths of transmitters and receivers at different nodes are arranged so that for any pair of nodes there is at least one common wavelength which is the same for one of the transmitter and receiver at one node and one of the respective receiver and transmitter at the other node, thus providing a direct connection between the nodes. The corresponding structure of optical add/drop multiplexer/demultiplexer for use at the network node, and method of providing direct connections between the nodes, are also provided.

Abstract: The invention relates to an optical fiber and a fiber termination which provide an output of laser light propagating through the fiber in a required direction while focusing it into a small spot. In one embodiment of the invention the termination includes a tapered fiber rod with an angled ball formed at the end of the rod. A corresponding method of manufacturing of the termination is provided. In another embodiment the termination includes a fiber rod having an angled end and a GRIN lens disposed so as to receive light reflected from the angled end, the lens being an integral part of the termination. In other embodiments the lens is replaced with a cylindrical or tapered multimode stub which provide similar function.

Abstract: An optical repeater is described which integrates an erbium doped optical fiber amplifier (EDFA) with a dispersion equalizer (DE) based on fiber gratings. The dispersion equalizer is based on parallel connection of a plurality of fiber gratings, or on parallel connection of a cascaded plurality of fiber grating branches, each branch carrying a plurality of gratings coupled in series. Each grating in each branch is chirped to provide selective reflection at one of the plurality of signal carrier wavelengths so that the total optical bandwidth of the dispersion equalizer is enhanced, i.e. the total bandwidth for a specific signal carrier wavelength is the combined optical bandwidths of the gratings which provide the reflection at the wavelength. The use of multiple gratings for each wavelength improves the optical bandwidth of the equalizer compared with single grating designs, enhancing the effective bandwidth.

Abstract: The invention relates to a differential current mirror circuit with low or eliminated differential current offset. The circuit comprises first and second input transistors Q1i and Q2i whose physical layout is being matched and emitters connected together to a first reference voltage Vref1 through an input resistance means Ri; first and second output transistors Q1o and Q2o whose physical layout is being matched and emitters connected together to a second reference voltage Vref2 through an output resistance means Ro; collector and base of the first (second) input transistor Q1i (Q2i) being connected to the base of the first (second) output transistor Q1o (Q2o) and to a first (second) input current terminal to which a first (second) input current i1i (i2i) is being supplied; and collector of the first (second) output transistor Q1o (Q2o) being connected to a first (second) output current terminal generating first (second) output current i1o (i2o).

Abstract: A data bus is provided having both a synchronous clock and a channel of data control information integrated in a single signal path. For a data bus having a particular bit time, the integrated clock and control signal has a clock high and low time in units equal to one bit time. One edge of the integrated clock and control signal is fixed in phase for bit timing, the alternate edge is phase-modulated. The phase-modulated clock edge carries framing and control data. The fixed-phase bit-timing edge regulates a DLL or PLL to extend the timing. The clock rate is preferably chosen to be equal to the multiplexing cycle rate of multiplexed data carried on the parallel bus.

Abstract: The invention relates to a variable optical attenuator having a profiled blade. It includes a mounting base with an actuator formed on the base, the actuator carrying the blade which is moveable across a light beam. The blade is profiled so as to provide a predetermined attenuation of the beam as a function of the displacement of the blade, the function being preferably substantially linear. As a way of example, first and second embodiments of the invention describe an electrostatic comb attenuator made of a semiconductor material and forming a monolithic structure. The embodiments relate to different blade profiles, having a protrusion and a notch at the front edge of the blade respectively. The attenuator device additionally includes light input and output lenses for receiving and directing light along a predetermined optical path. Other known type of attenuators having profiled blades, e.g.

Abstract: A method of cleaving a semiconductor wafer comprising a deep ion implantation induced selective area of exfoliation. The method includes steps of selectively masking the material with a mask having edges parallel to natural cleavage planes of the semiconductor material, implanting unmasked regions of the material with light ions of hydrogen or helium, and annealing to cause exfoliation of the material from the implanted regions. As a result of exfoliation, the patterned structure remaining on the wafer and pieces of the exfoliated material have high quality sidewall-facets which provides cleaved facets along the cleavage planes of the material. A method of manufacturing optoelectronic devices and semiconductor laser devices is provided.

Abstract: A photodetector has an extended wavelength range combined with high responsivity and reliability. It includes an active region having alternating compressive and tensile strain layers arranged so that the total effective strain of the active region is balanced. The thickness of each layer is limited so that a product of a thickness by strain is not exceeding about 20% nm to avoid formation of crystalline defects. The layers with higher optical absorption constant are made thicker than the layers with lower absorption constant to provide the required responsivity of the detector. In one embodiment, the active region is formed on InP substrate and includes alternating 0.25% compressive strain and 1.03% tensile strain layers of InGaAs composition, the compressive strain layers being approximately four times thicker. In another embodiment interfaces between the layers are compositionally graded. The described structure of the active region may be used in various types of photodetectors, e.g.