Abstract: An optical wavelength multiplexing apparatus is capable of controlling an attenuation amount of a variable optical attenuator at high speed, thereby preventing an optical level change generated by an upstream WDM section from flowing into a downstream WDM section. The high speed control is realized by providing a fast-operating local feedback loop for each variable optical attenuator in addition to a slower main feedback loop.

Abstract: A multi-channel optical switching system particularly usable as a programmable optical add/drop multiplexer in a multi-wavelength communication system. The switching system uses a grating operating at Littrow that separates a multi-channel optical signal into a plurality of optical channels, and combines a plurality of optical channels into a multi-channel optical signal. The system also uses a plurality of optical ports optically coupled to the grating and a selecting device to select which optical channel is directed to which of the optical ports.

Abstract: Methods and apparatus for generating a frequency comb and for its use in analyzing materials and in telecommunications. The frequency comb is generated by passing pulsed light from a laser through an optical fiber having a constriction. The frequency comb comprises a plurality of monochromatic components separated in frequency by a substantially constant frequency increment. The monochromatic components are used to probe materials for analysis. In preferred embodiments, the materials are DNA, RNA, PNA and other biologically important molecules and polymers. Optical responses are observed and used to analyze or identify samples. In telecommunication applications, the individual monochromatic components serve as carriers for individual communication channels that can carry information of any of a variety of types, such as voice, data and images.

Abstract: In a first aspect, a stream of data is transmitted by dividing the stream of data into a first substream and a second substream, transmitting the first substream in a first data channel, and transmitting the second substream in a second data channel. Before transmitting the first and second substreams, a first marker signal is inserted in the first substream and/or a second marker signal is inserted in the second substream. A receiver circuit receives the substreams, detects at least one marker signal, and reassembles the data stream from the substreams based on at least one detected marker signal. Numerous other aspects are provided.

Abstract: A method and system for using optical phase conjugation in an optical communications network including an add-drop multiplexer. The method includes determining a position for an optical phase conjugator such that channel quality for a channel in improved above a threshold. Transmission characteristics such as amplifier launch power or dispersion features may be adjusted to compliment the optical phase conjugation. An alternate method includes positioning the optical phase conjugator to improve a weighted average channel quality for the network.

Abstract: An optical interleaver for use in a range of telecommunications applications including optical multiplexers/demultiplexers and optical routers. The optical device includes an optical processing loop which allows multi-stage performance characteristics to be achieved with a single physical filtration stage. Optical processing on the first leg and second legs of the loop is asymmetrical thereby improving the integrity of the optical signals by effecting complementary chromatic dispersion on the first and second legs. A fundamental filter cell within the interleaver filters optical signals propagating on each of the two legs of the optical loop which intersects the fundamental filter cell.

Abstract: The subject invention pertains to a method and apparatus for multiplexing in optical fiber communications. The subject invention relates to a method and apparatus for spatial domain modulation in optical wavelengths. In a specific embodiment, the subject invention relates to a spatial domain multiplexer (SDM) for use with an optical fiber. Preferably, the input channels coupled into the fiber optic cable include collimated laser beams. The techniques of the subject invention can be utilized with single mode and multi mode waveguide structures, for example, single mode and multi mode optical fibers. The subject invention is applicable to step index optical fiber and to graded index optical fiber. Applications of the subject technology can include secure data links, for example, which can modulate data such that if the data is intercepted, the data cannot be interpreted. The subject methods and apparatus can also be used in conjunction with other multiplexing techniques such as time-domain multiplexing.

Abstract: A depopulated MEMs array based protection switch is provided. The protection switch includes a depopulated protection array for rerouting optical signals using fewer switching elements than a fully populated array, and in some implementations an integrated test array for performing a self-test in service mode, and for testing failed optical components.

Abstract: Optical equalization across N (an integer, N>1) channels of a multi-channel link of a communications network, is accomplished by averaging effects of optical performance variations within each of the M (an integer, M>1) parallel data signals. At a transmitting end node of the link, each one of the M data signals are distributed across the N channels of the link. Thus a substantially equal portion of each data signal is conveyed through the link in each one of the N channels. At a receiving end node of the link, respective bit-streams received over the N channels to are processed recover the M data signals. As a result, bit error rates of the bit-streams received through each channel are averaged across the M data signals, all of which therefore have a substantially equal aggregate bit error rate.

Abstract: A diffraction element having high diffraction efficiency and large wavelength-separation effect, which is excellent in mass-productivity and is formed by a simple process, is obtained. In a diffraction element having a rectangular grating formed in a surface of a transparent substrate whose cross-section is of an alternating recessed and projecting shape and each of the projecting portions is symmetrical, the period of the grating is equal to or smaller than the wavelength of incident light and the diffraction element is adopted so that the light is incident obliquely to its surface where the grating is formed.

Abstract: In an optical multiplexing interconnection module, first and second NRZ input signals synchronous by clock signal are inputted to its input section. The first NRZ input signal is converted to a first RZ signal according to a logical product with a clock signal CLK by a drive circuit and the second NRZ input signal is converted to a second RZ signal according to a logical product with an inversion clock signal by a drive circuit. Then, light emitting devices are driven according to the first and second RZ signals from these drive circuits and two optical signals from the light emitting devices are inputted to an optical channel and multiplexed therein and then, a multiplexed optical signal is transmitted through an optical channel.

Abstract: A multi-layer optical circuit has a plurality of optical circuit layers. Each optical circuit layer is positioned on a corresponding one of a plurality of substrates. An optical fiber extends between at least two of the optical circuit layers and forms a portion of the at least two of the plurality of optical circuit layers.

Abstract: Light of wavelengths ?2 and ?3 (?2<?3) is propagated in a first core. The light emitted form the first core is divided at a filter. That is, the light of the wavelength ?2 transmits through the filter and is made incident onto a third core while the light of the wavelength ?3 is reflected from a filter and is made incident onto a second core. The second core has a sectional area which works in a single mode for the light of the wavelength ?3 and works in a multiple mode for the light of the wavelength ?2. It is therefore possible to prevent noise or stray light in an optical multiplexer/demultiplexer.

Abstract: An optical node capable of automatically detecting its interconnectivity is disclosed. The node includes a light switch, a light source, light detector, a control circuit having a unique identification. The node sends its identification via each of its ports and also listens to each of its ports for identification from other nodes. The node may store the interconnectivity information, forward the interconnectivity information to another node, or forward the interconnectivity information to a path router.

Abstract: A monochromator for isolating or recombining a narrowband optical signal from a broadband signal. A cylinder with a continuous outer wall and two planar end surfaces is composed of a dispersive medium. The cylinder forms a multi-reflective cavity, wherein a broadband optical signal entering the cavity through an end surface at an angle of incidence to the outer wall is repeatedly totally internally reflected off the outer wall. The outer wall includes exit points for permitting egress of spectral components. For recombination, narrowband optical signals are coupled into the body at different locations on the outer wall and propagated in substantially helical paths that converge at an end surface. The propagation path within the dispersive medium can thus be lengthened in a relatively compact space. The monochromator has low insertion loss, and does not require fine adjustment or particularly careful handling.

Abstract: An optical architecture is provided comprising at least one broadband light source, a mod/mux unit, and a plurality of premises stations in communication with the mod/mux unit via an optical distribution hub. The mod/mux unit is configured to permit selective modulation of demultiplexed components of a target wavelength band of an optical signal, multiplex the selectively modulated optical signal, and direct the target wavelength band and a bypass wavelength band of the multiplexed optical signal to the optical distribution hub. The optical distribution hub comprises an arrayed waveguide grating configured to demultiplex the multiplexed optical signal and distribute respective distinct wavelength portions of the target wavelength band and respective distinct wavelength portions of the bypass wavelength band to respective ones of the premises stations.

Abstract: A receiving apparatus comprises a first waveform degradation compensating unit, a second waveform degradation compensating unit, a received waveform measuring unit for measuring waveform data on a received signal, a control unit for controlling compensation characteristics of the first and second waveform degradation compensating units to minimize a difference between frequency data obtained by converting the obtained received waveform data into a frequency domain and frequency data on a reference waveform free from waveform degradation, and time-constant generating units for making a difference in compensation characteristic control speed between the first and second waveform degradation compensating units. This realizes high-accuracy compensation for waveform degradation of a received signal stemming from chromatic dispersion, polarization mode dispersion or the like without employing a dispersion compensation fiber or a polarization maintaining fiber.

Abstract: A method and system for increasing the capacity and spectral efficiency of optical transmission includes pre-filtering optical pulses utilizing a bandwidth substantially proportional to the bit rate of the transmission system prior to propagating the optical pulses along a transmission fiber and post-filtering the propagated optical pulses utilizing a bandwidth substantially proportional to the bit rate of the transmission system.

Abstract: Two set of filter chips on the upper and lower surfaces, each of which has a wavelength characteristic corresponding to each wavelength component of wavelength-multiplexed light, are mounted on a transparent substrate to make an optical filter element. When the wavelength-multiplexed light is inputted to the optical filter element via an optical fiber and when the same light components as those having the wavelengths demultiplexed by an optical fiber is also inputted, the demultiplexed light and the replaced wavelength-multiplexed light will be obtained at another optical fibers, respectively.

Abstract: A WDM (Wavelength Divisional Multiplex) device is provided in which a client signal having a band that is greater than a band of a wavelength used for wavelength-division multiplexing is allocated a plurality of wavelengths and is transmitted as a wavelength-division multiplexed signal. The WDM device includes a used-band detecting part for detecting a used-band that is used by the client signal supplied from a client device. The used-band is detected from a path layer of the client signal using set-up information contained in the path layer of the client signal. The WDM device also includes a mapping part for mapping the detected used-band onto wavelengths used for wavelength-division multiplexing.

Abstract: An architecture is proposed for an optical node in a wavelength division multiplexed network. The optical node may be an optical add/drop node. Conventional add/drop nodes utilize a broadcast or blocking architecture. In a broadcast architecture, a copy of an optical signal is dropped to a drop path of a node while another copy continues on a through path. Thus, channels that occupy a specific portion of wavelengths (or spectrum) prior to the node are not available for use subsequent to the add/drop connectivity. In a blocking architecture, at least the through path (and often the drop path) is spectrally filtered. This permits wavelength reuse for add/drops in subsequent portions of the network. Disclosed is an optical node architecture that enables starting with a low cost approach, such as broadcast, but includes connections to permit ‘in-service’ upgrade to more capable architecture. Increasing spectral reuse is enabled through the architecture.

Abstract: A switch. The switch includes a port card. The switch includes a network connected to the port cards. The network having transmitters and receivers that communicate with each other and have assignments between each other. The switch includes a fabric connected to the port card through the network to send and receive fragments of packets to or from the port card. The port card, fabric and network have a plurality of modes of operation. The switch includes a control mechanism connected to the transmitters and receivers which changes the assignments according to the mode. The control mechanism changes the mode and reuses the transmitters and receivers where they can be reused. A method for switching fragments of packets. The method includes the steps of assigning assignments between transmitters and receivers of a network. Then there is the step of transferring the fragments of packets between fabrics and port cards with the transmitters and receivers of the network.

Abstract: An optical multi/demultiplexing circuit includes at least one phase generating optical coupler and an optical delay line coupled to the phase generating optical coupler. The phase generating optical coupler consists of at least one input and at least two outputs. At least one of the phase generating optical coupler has a wavelength dependent or frequency dependent output phase difference in the passband of the circuit so that it can change the transmittance characteristics of the optical multi/demultiplexing circuit.

Abstract: A method of splitting an optical data signal starting with an optical data signal split into n equal data sub-signals, and an optical binary auxiliary signal with the same bit rate and phase is added to each optical data sub-signal. Each nth bit of the optical binary auxiliary has a higher level, with the phases of each of the n optical auxiliary signals showing a relative displacement of one bit. As a result, n aggregate signals are generated, each of which is fed to a decision-maker. A decision-maker threshold is set above the amplitude of the data sub-signal and below the amplitude of the aggregate signal. Each decision-maker, therefore, emits an electrical data signal with 1/n times the bit rate of the data signal.

Abstract: A bidirectional optical triplexer is disclosed, which may be connected to an external optical waveguide and receives first and second optical signals having first and second wavelengths through the external optical waveguide, and transmits a third optical signal having a third wavelength. The triplexer includes a platform having first and second trenches spaced from each other on a first optical path optically connected with the external optical waveguide, a first filter positioned in the first trench for reflecting the first optical signal proceeding through the first optical path to a second optical path, and a second filter positioned in the second trench for reflecting the second optical signal proceeding through the first optical path to a third optical path.

Abstract: There is provided an apparatus for performing, by optical code division multiplex access, at least one of encoding and decoding of wavelength-division-multiplexed light. The apparatus includes: an optical input/output section 203 for handling input/output of the wavelength-division-multiplexed light; and N fiber gratings (where N is an integer equal to or greater than two) 101 to 103, which are in a series connection to the optical input/output section 203. Each of the N fiber gratings has a sampled grating structure having an alternating array of first regions (11 to 14; 21 to 24; and 31 to 34) which provide a refractive index modulation with a relatively large amplitude and second regions (201) which provide a refractive index modulation with a relatively small amplitude, the first and second regions being disposed with a constant period P.

Abstract: A device wavelength division multiplex optical transmission system has the wavelengths of the optical carriers arranged so as to reduce the effect of in-band crosstalk which results from unwanted side bands to the carriers. Possible wavelengths are placed on an equally spaced wavelength grid, and the transmitted channels are organized into groups of three each of which is placed on four adjacent grid positions, one of which is unused. Adjacent groups are spaced apart by two or more vacant grid positions.

Abstract: A divider/combiner unit combines RF signals, then converts the combined signal into an optical signal and sends it over an optical fiber. N radio access units each convert the optical signal received from the optical fiber into an RF signal and transmits it from an antenna, and each radio access unit converts an RF signal received by the antenna into an optical signal and sends it over an optical fiber to the divider/combiner unit. The divider/combiner unit converts the received optical signal into RF signals and outputs them. This system is operated as plurality of communication systems in common to them in correspondence to a plurality of input/output terminals of the divider/combiner unit.

Abstract: A system for controlling the demultiplexing process in an optical backplane device has application to optical switching in high-speed digital communication routers and switches. In demultiplexing, a selected compressed data packet is extracted from a multiplexed stream of compressed packets by a modulator and decompressed. The modulator is controlled by a control signal. An error in the timing of the modulator control signal corresponds to a characteristic distortion in the decompressed signal. By monitoring the effect of timing errors on decompressed signals, steps can be taken to correct the timing errors by controlling delays in either the optical or the electronic parts of the switching device. The timing of modulator control pulses is thus continuously adjusted to minimize timing errors. Instead of monitoring just decompressed signals, calibration pulse trains of known value and suitable form can be inserted.

Abstract: An optical multiplexer and demultiplexer (mux-demux) (100) comprises a multimode waveguide (126) which communicates with first (122) and second (124) coupling waveguides. Multiplexed optical radiation comprising individual wavelength channels of appropriate wavelength introduced into the input waveguide is demultiplexed by means of modal dispersion and in-ter-modal interference with the multimode waveguide. The mux-demux consists of merely of waveguides and is therefore simple to fabricate and integrate with other components in integrated optical systems, and is capable of resolving channels having a small (˜1 nm) wavelength spacing. The mux-demux may be used without modification as a demultiplexer and remains of simple construction when scaled up to operate with many channels.

Abstract: The present invention provides for a method for optimizing the sequence of passive filter configuration in optical mux/demux devices for Wavelength Division Multiplex transmission systems and optical passive filter system obtained with that method, in which the optimization is obtained by taking care of the attenuation profile of the transmission optical fiber, and the variations of the spectral loss profile. The optimizing method permits to select the filter sequence maximizing the minimum span length of the network.

Abstract: An adaptive method is provided for applying chirp to an optical signal traversing through an optical network. The adaptive method comprises: applying chirp to an optical data signal at a transmitter in the optical network; transmitting the optical data signal through the optical network, the optical data signal having error detection data embedded therein; determining an error rate for the optical data signal at an egress point of the optical network, where the error rate is based on the error detection data embedded in the optical data signal; transmitting the error rate for the optical data signal to the transmitter; and adjusting the chirp being applied to the optical data signal at the transmitter based on the error rate for the optical data signal.

Abstract: A WDM transmission system including a plurality of WDM optical network and a central controller communicably connected to the plural WDM optical network via a plurality of monitor/control lines respectively, the central controller includes variation factor monitoring means for monitoring one or more variation factors of preemphasis on each WDM optical network and preemphasis controlling means for controlling a status of the preemphasis by adjusting the setting for the preemphasis performed on each WDM network via respective one of monitor/control lines. Therefore, preemphasis performed each of the plural WDM optical network can be automatically executed without boosting costs and loads on elements of each WDM optical network. Stabilized transmission of a WDM signal can be performed in each of the plural WDM optical network with ease without manual setting.

Abstract: An optical switching apparatus includes an optical switch having a plurality of input ports and output ports, optical amplifiers, monitor circuits, optical amplifiers monitor circuits, and a controller that controls the optical switch. The optical amplifiers are connected to the input ports of the optical switch. The monitor circuits are connected to the output ports of the optical switch. The controller selects one of the plurality of the monitor circuits based on predetermined rules to obtains the loss at the output ports and/or the differential loss between the channels of the optical switch. The controller further selects one of the optical amplifiers based on the configuration of the optical switch to compensate the loss and the differential loss among the different channels of the optical switch by pre-amplifying the optical signals before they reach the input ports of the optical switch.

Abstract: An optical switching apparatus includes an optical switch having a plurality of input ports and output ports, optical amplifiers, monitor circuits, optical amplifiers monitor circuits, and a controller that controls the optical switch. The optical amplifiers are connected to the input ports of the optical switch. The monitor circuits are connected to the output ports of the optical switch. The controller selects one of the plurality of the monitor circuits based on predetermined rules to obtains the loss at the output ports and/or the differential loss between the channels of the optical switch. The controller further selects one of the optical amplifiers based on the configuration of the optical switch to compensate the loss and the differential loss among the different channels of the optical switch by pre-amplifying the optical signals before they reach the input ports of the optical switch.

Abstract: An optical transport switching system having an all-optical switch that can be selectively configured to provide cross-connection and add/drop multiplexing functions. Optical circuit cards are provided in a chassis/bay, and connected by an optical backplane. The circuit cards may include access line interface cards, optical access ingress cards, transport ingress cards, transport egress cards, and optical access egress cards. An optical switching fabric provides selective optical coupling between the cards. The all-optical switch can be used in an optical network that allows external/access networks to access the optical network, including access networks that use Gigabit Ethernet or SONET signaling. Wavelength conversion is provided for non-compliant wavelengths of the access networks. A local area network enables control and monitoring of the cards by a local node manager.

Abstract: A planar lightwave circuit generalized for handling any given band of multiple bands of a wavelength range, including a first grating element handling a first group of bands; and a second grating element handling a second group of bands. The first and second groups of bands overlap in the wavelength range, and may be spaced apart by a fixed wavelength value. By providing two periodic grating elements handling alternating bands, their free spectral range is allowed to expand, improving their roll-off characteristics. By providing separate inputs for each band, wavelength accuracy can be improved. Device flexibility can be further improved by using switch and interleaver fabrics at the inputs and outputs. The resultant device, generalized to handle any given band within a wavelength range, eliminates the need for separate component design and inventory tracking otherwise necessary.

Abstract: An add-drop multiplexer is described, in one embodiment the add-drop multiplexer includes an optical transmission signal input port adapted to receive a wavelength division multiplexed optical transmission signal, an optical transmission signal output port adapted to output at least a portion of the wavelength division multiplexed optical transmission signal, an add-drop optical channel port adapted to receive an optical add channel and output an optical drop channel, and a wavelength selective optical filter arranged between the optical transmission signal input port, the optical transmission signal output port and the optical add-drop channel port. The wavelength selective optical filter reflects optical channels that will continue through the add-drop multiplexer along a transmission line to the optical transmission signal output port and permits an optical channel that is to be dropped to pass therethrough.

Abstract: A method and apparatus for multiplexing and demultiplexing optical signals. The apparatus includes first and second optical waveguides coupled via an optical coupler. The optical coupler has a coupling waveguide and an optical switching wedge attached to a piezoelectric actuator. In operation, first and second optical signals are received by the first and second optical waveguides, respectively. If the signals are to be combined, the optical switching wedge is moved to a first position where it is optically coupled to the first optical waveguide. The first optical signal is then transmitted, via the coupling waveguide, to the second optical waveguide, where it is combined with the second optical signal. If the signals are not to be combined, the optical switching wedge is moved to a second position where it is optically uncoupled from the first optical waveguide.

Abstract: A device for converting at least four parallel data streams on respective input data lines into one serial data stream on a fiber optic data line. The device includes a first multiplexer for multiplexing at least two of the parallel data streams into a first intermediate output stream and a second multiplexer for multiplexing at least two other of the parallel data streams into a second intermediate output stream. A serializing transmitter is coupled to the first and second multiplexers for serializing the first and second intermediate output streams into the serial data stream. A signal synchronizes the serializing of the first and second intermediate output streams and tags output data in the serial data stream as corresponding to data from each of the respective input data lines. In-band messaging is used to transfer commands and status messages between devices without affecting ongoing data stream communications.

Abstract: An optical network node is provided having add-drop and/or cross-connect functions, wherein the optical network node includes a first optical line with a first drop branch and a first add branch, and a second optical line with a second drop branch and a second add branch, wherein the first drop branch and the second drop branch are in each case connected to a first cross-connect and to a second cross-connect, the first add branch is connected to the first cross-connect and to the second cross-connect via a first wavelength converter, and the second add branch is connected to the first cross-connect and to the second cross-connect via a second wavelength converter.

Abstract: A laser device for medical treatment system, comprising at least a plurality of laser beam emitting sources, a laser beam multiplexing means for superimposing the laser beams emitted from the laser beam emitting sources, and a beam mixing means where the laser beams from the laser beam multiplexing means enter.

Abstract: A technique for performance-monitoring of a standard SONET signal involves first converting the optical signal to an electrical signal, removing in the framing signal time slot the framing signal for leaving only the framing signal noise in such time slot, and separating the framing signal noise from the data signal for viewing as a measure of the quality of the SONET signal.

Abstract: A first transmitting section frequency-multiplexes a data signal and a monitor signal, and then converts the resultant signal to an optical signal for output. A first receiving section converts the optical signal transmitted via a first optical transmission path and a wavelength demultiplexer into an electrical signal, and then extracts the monitor signal. A difference detector compares a monitor signal level with a predetermined reference level, and then outputs wavelength information to a second optical transmission path. Based on the wavelength information transmitted via the second optical transmission path, a first wavelength controller adjusts the wavelength of the optical signal for stabilization at a predetermined wavelength. Thus, it is possible to achieve a wavelength division multiplex transmission system capable of controlling the wavelength of the optical signal at low cost.

Abstract: The present invention provides an improved full-duplex optical communications system. The system includes: at least one office, where the at least one office provides a plurality of channels, the plurality of channels comprising a plurality of signal channels and a plurality of continuous wave (CW) channels; at least one optical add/drop multiplexer (OADM) optically coupled to the at least one office; and a subscriber premises optically coupled to the at least one OADM, where at least one of the plurality of signal channels and at least one of the plurality of CW channels are dropped from the plurality of channels to the subscriber premises by the at least one OADM, where the subscriber premises modulates the dropped at least one of the plurality of CW channels, where the modulated at least one of the plurality of CW channels is added to the plurality of channels by the at least one OADM.

Abstract: A spread polarization transmitter for transmitting at least one light signal comprises a spread-spectrum communication apparatus and a polarization modulator. The spread-spectrum communication apparatus modulates the at least one light signal according to a spread-spectrum modulation technique. The polarization modulator comprises a polarizer and a magnetic bubble waveguide. The polarizer is capable of polarizing the at least one spread-spectrum modulated light signal in a polarized direction. And the magnetic bubble waveguide, which is configured in accordance with a pseudo-random polarization code sequence such that the plurality of magnetic bubble domains assume a time varying position representative of the pseudo-random polarization code sequence, is capable of receiving at least one polarized, spread-spectrum modulated light signal.

Abstract: An optical cross-connect system is disclosed that use reduces the number of AWGs (Arrayed-Waveguide Grating) as compared to prior art systems so that the hardware complexity is reduced while simultaneously reducing its production costs. The optical cross-connect system includes N×N AWGs for performing multiplexing/demultiplexing functions, an optical circulator for transmitting bidirectional signals via the AWGs, an optical coupler for interconnecting N individual ports of the AWGs, and an optical switching block connected to the optical coupler. One of the optical signals branched from the optical coupler is input to the optical switching block having a corresponding wavelength and distributed to a desired output terminal, and the other one of the optical signals is input to an optical switching block being out of an operable wavelength range and filtered by the optical switching block.

Abstract: An optical ring is provided for propagating optical signal pairs over wavelength connections between nodes. Each optical signal pair includes two signals at different wavelengths. At one or more of the nodes, one signal of the pair acts as a transmit signal and the other acts as a receive signal. If a failure is detected the optical signal pair is redirected over a protection path without changing the wavelengths of the transmit and receive signals. This may be achieved by reversing a propagation direction for each of the signals comprised by the redirected optical signal pair.

Abstract: The present invention is directed toward a distributed intelligence fiber-optic communication network in which node control processors (NCPs) associated with each network element periodically transmit identification and status information to the other NCPs in the network. Various faults in the network can thus be readily identified, and appropriate tasks for modifying the network in response to the fault (such as rerouting around a defective network element) can be carried out. Further, information continues to be distributed among the NCPs even if a break occurs in a segment of fiber in the network.

Abstract: The present invention relates to a bidirectional add/drop multiplexer (BADM) and a bidirectional add/drop amplifier (BADA) module. The present invention includes an N×N arrayed waveguide grating router (AWGR), two optical circulators, two wavelength selective couplers, two optical isolators, and a mid-stage device. The mid-stage device comprises a means for compensating the chromatic dispersion of the optical fibers, a means for flattening the spectral response of the optical amplifiers, a means for suppressing the accumulation of the ASE noise or a combination of these means.