Abstract: An optical internet router apparatus uses optical tags to send and receive command and response messages between routers of an optical network for establishing, maintaining or changing a packet data connection over the network between a source router and a destination router. The optical router comprises (1) optical tag apparatus for reading a message and writing a message modulated on one or more wavelengths which are used for communicating with another router of a network connection, the control message being modulated onto the one or more wavelengths using a secondary modulation scheme which is different from a primary modulation used to modulate packet data; and (2) a controller responsive to a received read message for controlling a network connection at this router, and for generating a network control message to be written by the optical tag apparatus, the generated message controlling a network connection to said another router.

Abstract: A stack of two or more birefringent crystals having complimentary properties is arranged to have zero net beam walk-off at off-normal incidence and a finite free-spectral range. In another embodiment, the birefringent crystal materials are selected to provide reduced temperature dependence. The result is an optically and mechanically stable composite birefringent crystal unit. A variety of folded birefringent filters are implemented using the composite birefringent crystal.

Abstract: A wavelength slicer uses a waveguide grating router having a periodic arrangement of reflectors in the output circular boundary of the router, which causes each input signal to pass twice through the router. The slicer includes two interleaved sets of equally spaced reflectors. Each set is slightly displaced from the output curve, and their displacements are properly chosen so as to effectively produce a phase shift of &pgr;/2 between the reflected signals. The reflected signals again pass through the router to produce two separate signals, containing respectively the even and odd channels of the input signal. A second slicer embodiment is realized using two gratings that are coupled to elliptical and circular reflectors. A wavelength filter is realized by forming on the output curve a set of equally spaced reflectors with spacing equal to an integer fraction of the spacing of the images.

Abstract: An optical local area network uses modified remote network interface cards (NICs) to provide an optical carrier signal for signaling use by a centralized optoelectronic switch unit. The NIC optical transceiver is modified so that instead of being normally “off” during the standby mode, the data signal is logically inverted to be “on.” Light from each NIC is used to provide optical power for a corresponding optical modulator on the switch unit.

Abstract: A programmable broadband N×N cross-connect switch includes an N×N wavelength coupler combined with N tunable lasers, N modulators and N optical receivers. Each of the N tunable lasers can selectively produce N different wavelengths. The coupler couples the N wavelengths to the N modulators. The N modulators modulate the N wavelengths using N input electrical signals, each modulator being selectable by choosing a laser wavelength. The N optical receivers receive and detect the N modulated wavelengths to produce N output electrical signals therefrom, each receiver receiving and detecting a different one of the N different wavelengths. By selecting a laser wavelength a particular modulator and receiver is selected so that a modulated signal, formed at the selected modulator when an input electrical signal modulates the selected wavelength, is switched to the selected receiver.

Abstract: An N×N crossconnect switch, for large N, is implemented using an arrangement of smaller wavelength routers combined with space switches. An N×N crossconnect switch is constructed in three stages, using a plurality of input space switches, a plurality of (N/m)×(N/m) router (whose reduced size N/m allows efficient realization in integrated form), and a plurality of output space switches. In the router, the number of wavelengths is reduced by a factor m. The input and output space switches can be implemented using crossbar or Clos type construction. In one arrangement each modulator is combined with a small space switch consisting of 2×2 elements. Each space switch can be realized with negligible crosstalk by using a dilated arrangement.

Abstract: An optical signal access apparatus responds to variations in network traffic by dynamically assigning the number of wavelengths at originating and terminating optical signal access apparatus. A controller of an optical signal access apparatus monitors network traffic by checking the occupancy level (or other parameters) of data buffers and determines therefrom the number of optical signals that should be allocated to handle the network traffic from those buffers. When the optical signal access apparatus is part of a router it can be used to control traffic at the router as well as on the links between the routers of an optical network.

Abstract: A wavelength division multiplex (WDM) cross-connect architecture that can selectively cross-connect, at a wavelength granularity, wavelength channels from any of a plurality of input WDM optical facilities (e.g., fibers) to any of a plurality of output WDM optical facilities. The architecture is based on multi-wavelength modules, which are capable of routing simultaneously N wavelengths. The number of required modules scales only with k2 or less (i.e., k2 modules with N complexity), where k is the number of input/output fibers. The significant reduction in complexity is traded for a decrease in blocking performance; one of the disclosed architectures is strictly non-blocking in the space domain and rearrangeably non-blocking in the wavelength domain, whereas two others are rearrangeably non-blocking in both the wavelength and space domain.

Abstract: An optical router includes a capacity utilization unit which determines a packet capacity utilization level of each of a plurality of wavelengths being received at the optical router and a packet combiner unit which combines packets from the two or more wavelengths onto only one of those wavelengths for transmission from the optical router when the combined determined packet utilization level on the two or more wavelengths is less than a predetermined packet utilization level. According to one feature, the router also determines the destination of the packets on each of the wavelengths and only combines the packets of two or more wavelengths if their packets have the same next-hop router or the same termination router destination.

Abstract: A technique is described for determining the performance of substrate-side emitting VCSELs formed on a wafer. The technique involves forming top-emitting VCSELs on the same wafer as bottom-emitting VCSELs and then testing the top-emitting VCSELs and using the results to determine the performance of the bottom-emitting VCSELs of the wafer.

Abstract: An imaging arrangement technique is used to align a first waveguide on a first wafer to a second waveguide on a second wafer. The adaptive imaging arrangement is used on both the first and second waveguides when the first and second wafers are orthogonal to each other. In one embodiment, my imaging arrangement is used in an N×N optical cross-connect constructed using orthogonal abutting input and output planar arrays of N switches. If N is not too large, the optimum construction involves only two stages of trees, each incorporating an adaptive imaging arrangement allowing the input and output trees to be directly joined together without need for precise alignment.

Abstract: An optical switch comprises a programmable optical polarization unit (POLCON) which receives an input optical signal and selects an output signal polarization in response to a control signal. A polarization beam splitter (PBS) splits the selected polarization signal from the POLCON into a first and second orthogonally polarized signals. A feedback circuit couples a feedback signal indicative of the optical signal strength of at least one of the orthogonally polarized signals back to the POLCON which uses it to adjust the output signal polarization. The optical switch may be used with input optical signals having fixed or varying polarizations by utilizing a single or two feedback signals, respectively. The optical switch may be used as an optical Add/Drop unit or incorporated as part of a wavelength division multiplexed (WDM) signal Add/Drop unit.

Abstract: A dilated N×N optical cross-connect switch suitable for large N exhibits good efficiency (element count) without a significant increase in and reduced small depth (low loss) and crosstalk. The present arrangement consists of six levels of binary trees of 1×2 and 2×1 elements. The first two levels form the input stage, the third and fourth levels form the center stage, and the fifth and sixth levels form the output stage. In each of the input, center, and output stages, the odd number level is formed as a binary tree of 1×2 elements and the even numbered level is formed as a binary tree of 2×1 elements. Each stage is formed by directly joining together the 1×2 element binary tree with the 2×1 element binary tree. In one embodiment, depth is substantially reduced by using a symmetric arrangement of one or more 2×2 elements located in the vicinity of each junction between adjacent stages.

Abstract: A design technique minimizes the loss and ripple in the spectral response of an optical filter formed using a pair of gratings connected by an array of optical elements. This filter can be, for example, two waveguide grating routers (WGRs) connected by an array of waveguides. Each WGR includes two star couplers connected by waveguide grating arms. The smoothest spectral response is achieved for a given set of connecting waveguides, by choosing the number of grating arms less than or equal to filling the star coupler central Brillouin zone made by the set of connecting waveguides resulting in the connecting waveguides neither substantially over- or under-sampling the optical spectrum from the waveguide gratings. Exactly filling the Brillouin zone with the grating arms minimizes the loss, and so is the preferred choice.

Abstract: A wavelength selective polarization beam device uses waveguide grating routers (WGRs) having birefringent grating waveguides. When the device is used as a splitter it separates different wavelength channels of a wavelength division multiplexed (WDM) signal as well as the orthogonal polarization components of each wavelength channel. Since the WGR device is reciprocal, it can also be used as a combiner to combine the orthogonal polarization components of each wavelength channel into a WDM signal.

Abstract: The passband of an optical wavelength router is widened by using a combination of two grating apparatuses with opposite angular dispersions. The passband width approaches the channel spacing, with minimal loss penalty. This technique is particularly attractive for applications requiring a large number of ports with maximum passband width and relatively small loss. The optical wavelength router may be formed using either reflective or transmissive elements formed using grating apparatuses that are free space optical elements or waveguide gratings.

Abstract: A common Modular Carrier (MC) unit shares power and control among a plurality of Optical Network Units (ONU) which are plugged into it, thereby increasing the ONU density in an existing equipment shelf. In one embodiment, the MC unit together with its four ONU units is arranged to slide into an existing card slot of the existing equipment shelf and occupy the space of the adjacent slot. The result is a doubling of the capacity over the conventional technique of using a separate slot for each ONU unit.

Abstract: A double-pass birefringent filter apparatus comprises an external-interface apparatus (illustratively including of a beam-displacer element and a waveplate element); a birefringent filter comprised of a series of several birefringent waveplates; and a wrap-around unit (illustratively comprised of a beam-displacer element and a retro-reflector). In response to an input beam received at the external-interface apparatus, the double-pass birefringent filter forms two output beams having complimentary intensities which vary periodically with frequency.

Abstract: Feedback instabilities arising from interactions between automatic control loops at the amplifier nodes of an optical network are eliminated by restricting operation to a single amplifier node at a time. Amplifier node activation is accomplished using a global control signal which is sequentially passed from an upstream node through all of the nodes of the system. By controlling the state of the global control signal, an upstream node has operational priority over downstream nodes.

Abstract: Resonances in cross-phase-modulation (CPM) impairment occur in wavelength-division-multiplexed (WDM) transmission systems, having multiple equal dispersion-length amplifier spans, when channels have an integral number of bit walk-throughs per amplifier span. The CPM resonances are reduced by mis-matching the amplifier span lengths (and/or dispersion in each span) so an integral number of bit walk-throughs do not occur in successive amplifier spans. The CPM resonances are reduced by adding different lengths of dispersion-compensating fiber to each span, using different modulation bit rates and/or clock phase delay for each channel, and using different wavelength-selective clock phase delays for each channel.