Abstract: A communications network having two complementary optical networks each connectable to a headend, each optical network comprising a plurality of periodic interleaving filters serially connected by optical waveguides such that an output port of one periodic interleaving filter is couple to an input port of another periodic interleaving filter, and wherein an input or output node of the network is formed by a non-serially connected input or output port of a periodic interleaving filter.

Abstract: An autoprotected optical communication ring network is disclosed. The ring network includes two optical carriers that are arranged for bidirectional transmission. Multiple optically reconfigurable nodes are connected along the optical carriers. The nodes communicate in pairs, defining non-overlapping working links. Under normal conditions, the nodes of each pair are optically configured to exchange optical signals over the working link at a first wavelength on the first carrier and at a second wavelength that is different from the first wavelength on the second carrier. During a failure condition, the first wavelength on the second carrier and the second wavelength on the first carrier are reserved for effecting a protection scheme, while the first wavelength on the first carrier and the second wavelength on the second carrier can still be used for unaffected working links.

Abstract: A node device of an optical ring network is disclosed. With the node device, a counterclockwise auxiliary wavelength supplied from a third switch part is returned and supplied to a clockwise add/drop part when there is a fault in an optical transmission path on a left side, a clockwise auxiliary wavelength supplied from a second switch part is returned and supplied to a counterclockwise add/drop part when there is a fault in an optical transmission path on a right side, a clockwise active wavelength supplied from a clockwise add/drop part is returned and supplied to a first switch part when there is a fault in the optical transmission path on the right side, and a counterclockwise active wavelength supplied from the counterclockwise add/drop part is returned and supplied to a fourth switch part when there is a fault in the optical transmission path on the left side.

Abstract: The present invention relates to an optical communication system including a structure for suppressing deterioration of transmission characteristics of signals added at each of nodes arranged in an optical transmission line, and a method of assigning signal channels. The optical communication system includes the optical transmission line for transmitting signals of plural channels between a transmitter and a receiver, and one or more nodes are arranged at predetermined positions of the optical transmission line. Each of the nodes includes an ADM for adding signals of a predetermined channel to the optical transmission line, and a signal channel at which the absolute value of accumulated-dispersion up to the receiver becomes smallest among signal channels which can be added is assigned to each of the nodes in advance or dynamically.

Abstract: A node in an optical communications network receives optical packets at its input. It determines a priority assigned to each optical packet. When the optical packet is a transit packet destined for another node then, if the packet is determined to have a relatively higher priority, it is output from the node via a continuous-flow transmission path. Other transmit packets having relatively lower priorities are sent via an alternative transmission path that may include queues or buffers resulting in a variable delay.

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 reconfigurable optical blocking filter deletes a desired optical channel(s) from an optical WDM input signal, and includes a spatial light modulator having a micro-mirror device with a two-dimensional array of micro-mirrors that tilt between first and second positions in a “digital” fashion in response to a control signal provided by a controller in accordance with a switching algorithm and an input command. A collimators, diffraction grating, and Fourier lens, collectively collimate, separate and focus the optical input channels onto the array of micro-mirrors. The optical channel is focused on the micro-mirrors onto a plurality of micro-mirrors of the micro-mirror device, which effectively pixelates the optical channels. To delete an input channel of the optical input signal, micro-mirrors associated with each desired input channel are tilted to reflect the desired input channel away from the return path.

Abstract: A tunable (reconfigurable) OADM provides multiple drop ports and multiple add ports by which desired channels can be removed from, or added to, a composite optical signal. In one embodiment, a programmable demultiplexer is arranged to receive an input signal containing components at x different wavelengths from an optical input port, and distribute the input signal components among K output ports. K?1 of the output ports are the “drop” ports of the OADM, and cumulatively contain w different wavelengths. The remaining port, which is the “through port” that carries the z wavelengths not dropped from the original input signal, is connected to the first port of an M port programmable multiplexer having M?1 other input ports. The remaining M?1 ports are the “add” ports of the OADM, which cumulatively receive v different wavelengths to be added by the OADM.

Abstract: A method of controlling a network (115) through which information is transmitted in channels (?1, ?2, . . . ?n) among nodes includes: (a) providing at a node a device (108) for removing from the network (115) and replacing on the network (115) a selected one (?i) of the channels, the device (108) including a first input port from the network (115) to the node and a first output port from the node to the network (115); (b) taking a measure of the strength (P?iDROP) of the received channel (?iDROP); (c) regenerating the channel (?iIN); (d) adjusting (114) the strength (P?iADD) of the regenerated channel (?iIN) to approximate the strengths of the remaining channels ((?1, ?2, . . . ?n)-?i; and (e) combining the regenerated and strength-adjusted channel (?iADD) with the remaining channels ((?1, ?2, . . . ?n)-?i) at the output port.

Abstract: The invention relates to wavelength division multiplexing (WDM) and demultiplexing of optical signals using optical filters in free space. To minimize dispersion, the present invention uses relatively small angles of incidence. To avoid the need for a large package, the present invention utilizes reflective prisms to steer the reflected beams to provide a lateral shift in the beam path that ensures that the necessary space is provided between the input/output ports. Devices including a single adjustable filter are disclosed, along with devices having a plurality of filters.

Abstract: An East-West separable ROADM particularly usable as a programmable N×M optical add/drop multiplexer with an efficient pass through of optical channels in a multi-wavelength communication system. The East-West separable ROADM uses a grating that separates multi-channel optical signals into a plurality of optical channels, and combines a plurality of optical channels into multi-channel optical signals. Programmable mirrors and beam steerers can direct each optical channel to any of a plurality of fibers coupled to the device.

Abstract: Lasing of an optical channel at a particular wavelength is substantially prevented in an optical ring network by automatically verifying the presence of a break, e.g., termination, in the ring for an optical channel of a particular wavelength before allowing a node in the network to establish a “pass through” connection for that optical channel. More specifically, a node attempting to establish a “pass through” route for an optical channel received from another node is prevented from establishing the necessary connections to do so until it is confirmed that the optical channel of interest has been added to the ring or dropped from the ring at another node, thus indicating the presence of a “break” in the optical ring for that optical channel of interest.

Abstract: Optical systems of the present invention include an add/drop device and/or cross-connect device, which is reconfigurable to add and drop signal wavelengths between one or more transmission paths. The add/drop device includes a first selective element configurable to pass a first group of signal wavelengths including at least a first signal wavelength from an input path to a first add/drop path and pass continuing signal wavelengths differing from the first group of signal wavelength to a second add/drop path. A second selective element is provided that is configurable to pass a second group of signal wavelengths including at least a second signal wavelength from said first add/drop path and continuing signal wavelengths differing from the second group of wavelengths from said second add/drop path to an output path.

Abstract: A plug-in, optical add/drop (OAD) device includes a filter for adding and dropping a light beam of wavelength (?k) from a combined light beam having individual beams of different wavelengths (?1 . . . n). Several devices can be selectively integrated to create an optical communications system that will handle “n” different optical communications circuits. In operation, the devices are individually connected (plugged-in) to a GBIC, and they are serially connected (plugged-in) to each other. Consequently, immediately upstream from a device, the combined light beam includes wavelengths (?1 through ?n). On the other hand, the combined light beam immediately downstream includes (?1 through ?k?1 and ?k+1 through ?n).

Abstract: An optical carrier drop/add transmission system and method for adding a signal to multiplexed input optical signals conveyed by an optical multiplex input line. The multiplexed input optical signals are demultiplexed to provide isolated input optical signals to an optical switch matrix comprising switches in an array of lines and columns, the isolated input optical signals being inputted in a direction parallel to a line of switches in the optical switch matrix. The added optical signal is input in a direction parallel to a column in the optical switch matrix. An output line is selected and the switch that is on the column on which the added optical signal is inputted and on the selected output line is switched.

Abstract: An optical add/drop multiplexer may be formed using ring resonators. In some embodiments, ring resonators may be used instead of Bragg gratings in a Mach-Zehnder interferometer configuration. One or more wavelengths may be added or dropped or a band pass of wavelengths may be added or dropped in a wavelength division multiplexed system.

Abstract: An optical fiber ring is provided carrying a plurality of WDM optical signals, each at a respective one of a plurality of wavelengths. Each optical signal carries data associated with a corresponding group of TDM add/drop multiplexers coupled to an optical path spaced from the optical fiber ring. The optical signals are extracted from the fiber ring with optical add/drop multiplexers, and the data carried by the optical signals is then supplied to the corresponding group of TDM add/drop multiplexers. Accordingly, instead of assigning an optical add/drop multiplexer to each TDM add/drop multiplexer, the optical add/drop multiplexers are assigned to respective groups of TDM add/drop multiplexers. As a result, optical loss as well as cost of the WDM ring are minimized.

Abstract: In accordance with a dynamic and recursive method, the number of required ADMs for a given set of light-paths in an OWDM ring network can be minimized. In one formulation of the minimum ADM problem, the method aims to create as many circular segments among the set of light-paths in the OWDM ring network as possible, and to form as few non-circular segments as possible from the remaining light-paths such that the number of shared ADMs can be maximized. In one example, the method of the invention operates in two phases: in the first phase, a dynamic and recursive searching for all the possible circular segments among the light-paths is employed, after which the concatenated circular segments are removed from further processing. Next, a reverse recursive searching among the remaining light-paths for concatenated non-circular segments with as many light-paths as possible is conducted.

Abstract: Apparatuses, methods, and systems are disclosed for controlling optical signal wavelength spacing by providing for simultaneous upconversion of a plurality of electrical signal on subcarrier frequencies of an optical carrier frequency with or without modulation of an electrical data signal onto the optical carrier frequency. The optical carrier lightwave is split into a plurality of split lightwaves upon which one or more electrical frequencies carrying information can be upconverted onto optical subcarriers of the lightwave carrier frequency. The relative spacings of the optical subcarrier lightwaves will thus be unaffected by variation in the carrier frequency. The optical subcarrier lightwaves can then be recombined to form the optical data signal carrying the plurality of information carried by the electrical frequencies.

Abstract: An optical add/drop multiplexing unit (16, 116) includes a demultiplexer (53, 153) which optically isolates component signals of an optical input signal from an optical input terminal (22, 122). A plurality of switching units (61, 161) can optically couple either of two outputs to either of two inputs. One input of each switching unit receives a respective component signal from the demultiplexer, and the other is coupled to a respective protection input terminal (42, 142) of the multiplexing unit. One of the output terminals of each switching unit is coupled to a respective protection output terminal (43, 143), and the other is coupled to a respective input of a multiplexer (82, 182). The multiplexer has an output coupled to an optical output terminal (23, 123) of the multiplexing unit, and optically combines the signals at its inputs into an optical signal for its output.

Abstract: Embodiments of the invention generally provide a method for automatically detecting and provisioning new optical connections in a network element (NE). The detection of the optical connections is generally accomplished via optical scans, and in particular, an optical spectral analysis type scan, which may be conducted at specific times and at specific points within the NE in order to determine an association corresponding to a new connection through the NE. The automatic detecting in provisioning method of the invention may generally be implemented on connections in end terminals (ET), as well as connections in optical add/drop multiplexer (OADM) NEs. As such, embodiments of the invention allow for automatic detection and provisioning of optical circuit packs in an optical line system (OLS) based upon optical scans configured to detect the presence of valid incoming client signals through the NE.

Abstract: A phased-array device for wavelength division multiplexing/demultiplexing, comprising at least one input channel, a plurality of output channels, and an irregularly sampled array of phase modulators between the input and output channels, the irregular array having a configuration and phase modulation such that effectively only one beam at a given wavelength is focused onto a given output channel. In one embodiment the individual phase modulators are randomly spaced, their relative locations being determined by establishing a set of initially chosen locations, shifting each initial location by a random increment resulting in delay within one wavelength if the initially chosen locations are not sufficiently random, and then adjusting each shifted location a fraction of a wavelength such that the overall phase shift to a desired image point on one of the output channels equals a constant value.

Abstract: A system and method for optical power transient control and prevention in communication networks. An optical signal propagating on a network is demultiplexed into individual spectral bands, e.g. at an OADM, and an optical power monitor point is included into each band. A separate idler laser is provided for each OADM band. The power output of each laser is adjusted such that it compensates for the signal power lost from each band. The wavelength of each laser is chosen to fall within the associated OADM spectral band, but outside of the window of individual signal wavelengths, so that it may propagate through the network without causing deleterious interference at the receiver.

Abstract: The present invention relates to a dispersion compensating module or the like having a simple and compact structure. The dispersion compensating module comprises a plurality of dispersion compensators between its input and output ends and at least one or more optical switches disposed between these dispersion compensators. Each of the optical switches acquires signals reached from its first port and is switching-controlled so that the signals are outputted from one of its second and third ports. The dispersion compensating module controls the port switching operation of at least one of the optical switches, thereby adjusting the propagation line of the signals, i.e., the dispersion compensation amount.

Abstract: To improve a power balance of an optical add multiplexer, an add amplifier is optically coupled to an add path of an optical add module. A through loss associated with a signal passing through the add module, and an add loss associated with a signal travelling an add path of the add module are known or otherwise calibrated values. An input power measurement of the signal input to the add module is used in conjunction with the through loss, add loss, and number of added channels to determine an add path amplification value. The gain of the add amplifier is controlled according to add path amplification value so that the power level of added channel(s) substantially matches the power level of the WDM signal output from the add multiplexer. Furthermore, the gain profile of the add amplifier preferably matches a gain profile of a signal input to the add module.

Abstract: A multiple-channel passive DWDM multiplexing module, which can be installed in a standard shelf of a patch panel, takes multiple optical signals of defined frequencies and provides a multiplexed optical output. The module simplifies greatly intraoffice fiber optical connections by situating itself adjacent where the fiber optical cables are terminated, thus eliminating fiber optical cable routing through overhead racks. The module saves inter-office fiber optical resources by providing passive DWDM multiplexing, which combines multiple optical signals into one fiber optical cable. The module further saves cost on spare parts at each central office by providing a maintenance connections that can be alternately used as a spare input connection.

Abstract: A system for accessing a wavelength-division-multiplexed (“WDM”), bidirectional optical fiber ring network having first and second network fibers for carrying WDM signals in opposite directions. The system includes a network node intersecting the first and second fibers of the ring network. The network node is coupled to a network access station through a single pair of access fibers. The network access station has a single array of receiving elements and a single array of transmitting elements. The network node has two wavelengths add drop multiplexers (“WADMs”) each having a first input, a second input, a first output and a second output. The WADMs can be each individually set to a bar state or cross state for each one of the wavelengths on the ring network.

Abstract: An optical wavelength division coupler 11 wavelength-divides a wavelength multiplexed light to respective wavelength lights each of which is dropped to an optical gate switch 15-i (i=1˜n) and a light receiver 13-i by an optical coupler 12-i and supplied to an optical light fault monitor 14 through the light receiver 13-i. When the optical signal deterioration monitor 14 detects an optical loss of wavelength (OLOW), an optical loss of signal (OLOS) or an optical signal degrade (OSD) in wavelength lights processed by the optical coupler 12-i as a fault detection signal in an optical layer, a controller 19 controls the optical gate switch 15-i to cut off wavelength light passing therethrough and sends an optical alarm indication signal (AIS-O) to a downstream side. Therefore, when a loss of signal is detected by the light receiver 13-i, the optical signal deterioration monitor 14 can know the alarm indication signal (AIS) from the upstream side, removing the necessity of special hardware therefor.

Abstract: A communications network has a plurality of nodes interconnected by an optical transmission medium. The transmission medium is capable of a carrying a plurality of wavelengths organized into bands. A filter at each node for drops a band associated therewith and passively forwards other bands through the transmission medium. A device is provided at each node for adding a band to the transmission medium. Communication can be established directly between a pair of nodes in the network sharing a common band without the active intervention of any intervening node. This allows the network to be protocol independent. Also, the low losses incurred by the passive filters permit relatively long path lengths without optical amplification.

Abstract: To improve a power balance of an optical add/drop multiplexer, an add amplifier is optically coupled to an add path of an optical add/drop module. A through loss associated with a signal passing through the add/drop module, a drop loss associated with a signal travelling a drop path of the add/drop module, and an add loss associated with a signal travelling an add path of the add/drop module are known or otherwise calibrated values. A dropped channel power measurement is used in conjunction with the through loss, add loss, drop loss, number of dropped channels and number of added channels to determine an add path amplification value. The gain of the add amplifier is controlled according to add path amplification value so that the power level of the added channel(s) substantially matches the power level of the WDM signal output from the add/drop multiplexer. Furthermore, the gain profile of the add amplifier preferably matches a gain profile of a signal input to the add/drop module.

Abstract: A method and apparatus for controlling the signal/noise ratio of optical add/drop signals in an optical WDM transmission system having a transmitter unit, a receiver unit and at least one optical add/drop multiplexer for transmitting optical express signals and at least one optical add/drop signal wherein the power spectrum of the pre-emphasized express signals is determined, and the signal level of the at least one optical add/drop signal is adapted to the power spectrum determined for the express signals.

Abstract: An optical component array allowing expansion of the occupied bandwidth on an existing optical transmission network without disrupting signal traffic. Wavelength selective filters (16, 30; 20, 34) and optical components, such as amplifiers (18, 32) are arrayed for use with a wavelength division multiplexed optical transmission system to transmit a selected portion of a transmission spectrum to an amplifier path and reflect the remainder of the spectrum. Wavelength selective filters and associated amplifiers are arranged in a cascade configuration with a bypass path (35, 37). Additional wavelength selective filters and amplifiers can be added in the bypass path without disrupting existing signal traffic, and such additions can provide for a remaining bypass path, thus allowing further expansion. This configuration provides an expandable amplifier array with a low initial cost.

Abstract: Router line cards are partitioned, separating packet forwarding from external or internal interfaces and enabling multiple line cards to access any set of external or internal data paths. Any failed working line card can be switchably replaced by another line card. In particular, a serial bus structure on the interface side interconnects any interface port within a protection group with a protect line card for that group. Incremental capacity allows the protect line card to perform packet forward functions. Logical mapping of line card addressing and identification provides locally managed protection switching of a line card that is transparent to other router line cards and to all peer routers. One-for-N protection ratios, where N is some integer greater than two, can be achieved economically, yet provide sufficient capacity with acceptable protection switch time under 100 milliseconds.

Abstract: Methods and apparatus for multiplexing and demultiplexing optical signals. An interleaver having a modified Mach-Zehnder interferometer as a first stage is used as a wavelength division multiplexer. This first stage is combined with one or more cascaded stages, each having a beam splitter and an optical delay element. A light beam including a number of signals at different wavelengths is received. The beam is split such that approximately half of each signal is contained in one of two sub-beams. One of the two sub-beams passes through a delay element, which provides a phase shift. The two sub-beams are recombined and split again. Each wavelength adds constructively or destructively in the new sub-beams such that the signals are separated—some wavelengths are in one of the new sub-beams, some are in the other. One of these sub-beams is delayed, and the two are combined and split again, improving the separation.

Abstract: The invention relates to an optical telecommunications network comprising several nodes (N1 to N4) connected to one another by optical transmission paths that form several working rings (R1 to R4), each of which passes via each node. Information is transmitted in the network at several different wavelengths. To ensure that the network can be implemented as cost-effectively as possible, it comprises a group of nodes (N1 to N4) including N nodes, a group of working rings (R1 to R4) including N rings, and a group of wavelengths (?1 to ?4) including N wavelengths in such a way that each node in the group of nodes is configured to transmit signals at one wavelength in the group of wavelengths to all rings in the group of rings except to the ring from which it receives signals, and to receive signals at all wavelengths in the group of wavelengths except for its own transmitting wavelength from both directions in only one of the rings in the group of rings.

Abstract: A system and method is provided for minimizing power fluctuations and crosstalk in a wavelength division multiplexed optical (WDM) network employing dynamic add/drop techniques by utilizing amplifiers operating in a nearly linear region. Conventionally, erbium-doped fiber amplifiers (EDFAs) are operated in saturation for providing signal amplification in a WDM network. Instead of using saturated EDFAs, the present invention includes optical amplifiers operated in a linear or nearly linear regime for providing signal amplification in a dynamic add/drop or bursty data WDM network. By operating optical amplifiers in a linear or nearly linear regime, power fluctuations, transients and crosstalk caused by adding/dropping or switching channels in the WDM network are minimized. Raman amplifiers, EDFAs, or semiconductor optical amplifiers (SOAs) can all be operated in a linear or nearly linear range to provide linear amplification in such a dynamic add/drop or bursty data WDM network.

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: A photonic switching apparatus includes primary photonic switching logic to perform photonic pass-through and add/drop functions and secondary photonic switching logic to reduce the effective number of add/drop interfaces and/or switch optical signal channels to and from clients or client adaptation devices.

Abstract: A WDM add/drop module for use in a network node of an optical network, the module comprising an optical drop unit for dropping a first wavelength signal travelling along a first path in the optical network traffic, a trunk receiver unit for converting the first wavelength signal into a first electrical signal, a tributary optical transmitter unit for converting an electrical input signal into a first optical signal for transmission along a tributary optical connection, wherein the output of the trunk receiver unit is connected to the tributary optical transmitter unit and to a first interface port of the WDM drop module for interfacing with another WDM drop unit, an electrical switch unit arranged in a manner such that, in use, selectively either the first electrical signal or a second electrical signal received at a second interface port of the WDM add/drop module from another WDM add/drop module is through connected to the tributary transmitter unit for conversion and transmission along the tributary optica

Abstract: A dispersive optical element and positionable micromirrors are deployed to implement a configurable wavelength routing device for add/drop and other applications. Input light is dispersed and imaged onto a focal plane where there is disposed an array of light redirection elements operative to decenter wavelengths on a selective basis. In the preferred embodiment, the dispersive optical element is a grating or grating/prism featuring a high degree of dispersion allowing the input and return paths to be parallel and counter-propagating, both for a compact size and to facilitate a lateral shifting in a localized area. The inputs and outputs may be implemented in conjunction with optical fibers, with a lens being used to collimate light prior to illumination of the grating. A focusing lens is preferably used to form a nominally telecentric image of the dispersed spectrum at the image plane.

Abstract: Wavelength division multiplex ring communication network equipment comprises a first multiplexer connected to a first optical fiber portion dedicated to transporting multiplexed signals and a second multiplexer connected to a second optical fiber portion. The equipment comprises signal protection circuitry connected to the first and second multiplexers and to a terminal which, in the event of local detection of interruption of signal transmission at a first wavelength on the first optical fiber portion, send the signals coming from the terminal to the second multiplexer at a second wavelength so that it communicates them to the second optical fiber portion, and sends to the terminal the signals that are addressed to it and that come from the second optical fiber portion at the second wavelength.

Abstract: A carrier is extracted from a stream of optical signals including plural wavelength division, multiplexed carriers modulated by corresponding signals while a carrier having the same wavelength as the extracted carrier is inserted into the stream. The stream of optical signals and the carrier to be inserted are coupled to a tunable wavelength selector having first wavelength and phase shift properties. Tuning of the wavelength selector is changed, so it has second wavelength and phase shift properties such that the entire stream of optical signals is coupled from an input port to an output port via the tunable wavelength selector, and the extracting and inserting operation is not performed while the tuning is changed. The other carriers are coupled from the input port to the output port via the selector while extracting and inserting are performed, and the selector has the first wavelength and phase shift.

Abstract: The architecture for a photonic transport network node provides for pass-through of selected channels in the absence of OEO conversion, dropping of selected other channels, and selective routing of the other dropped channels to a processing means that provides OEO conversion and 3R processing. Conveniently, these dropped channels may be multiplexed back into the switching fabric of the node to be directed in pass-through mode to any selected output destination port. The add channels are inserted at the input side of the node. In addition, a pass-through channels may selectively delayed and OEO converted if signal conditioning and/or wavelength conversion are required. The transponders, regenerators and transceivers need not be wavelength specific, allowing flexible and scaleable network configurations. This network node is upgradeable and can be augmented without disturbing traffic within the node.

Abstract: Devices and methods are provided for a re-configurable optical add/drop multiplexer (ROADM) having a static circulator, a selectable grating and a reversible circulator. The use of a reversible circulator in a known optical drop multiplexer configuration allows the selectable grating to be used for selecting both the add-wavelength and the drop-wavelength while maintaining an East/West architectural split to allow for SONET compliant maintenance. This invention provides a cost-effective enhancement to a duplex reflective wavelength selective ROADM.

Abstract: In a WDM optical network, optical components of optical add/drop multiplexers (OADMs) at different nodes are made independent of the optical channel wavelengths to be dropped and added. Groups of optical channels each comprise a respective channel in each of a plurality of optical bands of channels having adjacent wavelengths, and the OADMs use tunable optical filters to drop and add channels in a selected group. A remote source supplies unmodulated optical carriers at channel wavelengths via an optical carrier fiber to each node, and at least one, conveniently all, of the optical carriers in a respective optical band is/are modulated with a signal to be transmitted via the add filter.

Abstract: In tunable systems, during a tuning cycle, express channels or wavelengths are dropped as the system sweeps through its free spectral range (FSR) before stopping at the desired wavelength to be dropped. This is disadvantageous as the data information in the express wavelengths suffers a hit or momentary increase in bit error rate (BER). Techniques for eliminating or at least minimizing interference to those channels or wavelengths are disclosed. According to one aspect of the present invention, the wavelength selection to be dropped is done “off-line” and does not affect the express channels. An optical reference source is used to set up and tune a drop filter. Once the filter is set to the appropriate dropping wavelength, a secondary filter is scanned to cause the channels to be shunted to the drop filter. If the wavelength of a signal and the drop filter matches, the signal is dropped.

Abstract: A tunable optical add-drop multiplexer (OADM) based on an SOI (silicon-on-insulator) wafer is disclosed. The tunable OADM includes a multimode interference region, at least a grating formed on the multimode interference region, and at least two electrodes formed on two sides of the multimode interference region and having carriers induced thereinto, thereby a variation of an optical waveguide in the grating is controlled through controlling the carriers induced into the electrodes so as to further control different propagation of wavelength signals.

Abstract: An add/drop module is disclosed including a first circulator having first through third ports that are connected to an external optical fiber, the first circulator outputting an optical signal, input to the first port, to the second portand outputting an optical signal, input to the second port, to the third port, an optical multiplexer/demultiplexer having a multiplexing port connected to the second port of the first circulator, and adapted to provide a passage for the optical signal, and a plurality of demultiplexing ports respectively adapted to provide passages for demultiplexed channels associated therewith, and a plurality of add/drop units. Each add/drop unit includes a second circulator having first through third ports, a second port thereof being connected to an associated one of the demultiplexing ports, and an optical switch having first through fourth ports.

Abstract: Dividing a multiplexed optical signal transmitted along a first transmission path into two portions and diverting one of the two portions to a second transmission path and forwarding the other portion of the multiplexed optical signal along that first transmission path, while the energy of the diverted portion comprises the entire spectrum of the multiplexed optical signal. Preferably, the diverted first portion is further divided into at least two parts, each comprising a wavelength range substantially different than the others, and at least one of the two parts is forwarded towards an optical receiver.

Abstract: Disclosed is a bi-directional optical add/drop multiplexer connected to an optical fiber for transmitting optical signals multiplexed in a wavelength division multiplexing optical network and which performs adding/dropping of the optical signals. The optical add/drop multiplexer includes a first wavelength division multiplexer provided with a multiplexing port functioning as a path for forward or backward optical signals and with a plurality of demultiplexing ports, each functioning as a path of demultiplexed channels. A plurality of add/drop parts, each performing adding/dropping of preset channels, and connected with the demultiplexing ports of the first wavelength division multiplexer in one-to-one. A second wavelength division multiplexer connected with the plurality of add/drop parts in one-to-one, provided with a plurality of demultiplexing ports, each functioning as a path for demultiplexed channels and with a multiplexing port functioning as a path for forward or backward optical signals.