Abstract: An optical communication system includes a plurality of optical add/drop multiplexers (OADMs). The plurality of OADMs includes at least five low distortion OADMs. Each OADM is coupled between spans of a multiple span communication link and operable to receive a multiple wavelength signal. The multiple wavelength signal includes a plurality of bands of wavelength signals each separated from other bands of wavelength signals by one or more guard-channels. In one embodiment, each of the at least five low distortion OADMs adds/drops a common first band of wavelengths to/from the multiple wavelength signal. In some embodiments, a spectral distortion associated with a pass-through wavelength signal spectrally adjacent to one of the one or more guard-channels is no more than three decibels after exiting the last of the plurality of low distortion OADMs. In those embodiments, the guard-channel is adjacent to the first band of wavelengths.

Abstract: A module that includes both an “add-in”/“drop-out” pair of ports and a “drop-in”/“add-out” pair of ports comprises an arrangement of elements that combines an optical signal having a chosen wavelength with an optical signal applied at the “add-in” port, and outputs the combined signal at the “add-out port.” Concurrently, the module extracts an optical signal with the same wavelength from an optical signal applied at the “drop-in” port signal, yielding an optical signal at the “drop-out” port that is missing that same wavelength. When the amount of information that needs to be sent from a first network node to a second, remote, node, is greater than that which a single wavelength can handle, a plurality of the above-described modules are interconnected within the first node by optically coupling the “add” ports in a “daisy chain” fashion and the “drop” ports in a “daisy chain” fashion, with each module operating at a different wavelength.

Abstract: An optical switch for routing arbitrary wavelengths between optical fibers in optical networks. The optical switch may include a highly wavelength dispersive element together with a spatially dispersive element to separate the wavelengths. Broadband switch inputs and outputs may be provided for adding and dropping arbitrary wavelengths at each node of the network. Fiber demultiplexers and multiplexers may also be used to reduce the impact of mirror array yield on switch functionality.

Abstract: A device (D) is dedicated to controlling the power of optical signals in a transparent switching node of an optical communication network that switches bands of wavelengths. The device includes, firstly, a controller (12) for comparing input optical power measurements to a selected first threshold and generating instructions representative of the comparison result, secondly, a measuring device (10A) for delivering measurements representative of the input optical power of the optical signals at one output at least of the switch (4), and thirdly, a processor between the switch (4) and the multiplexer (6) of the node and which control the optical power of the signals coming from the switch (4) as a function of the instructions they receive, so that the optical power of the signals at the input of the multiplexer (6) is maintained substantially constant.

Abstract: A method and system for providing tandem protection in a communication system. Path protection is provided using at least two redundant communication paths and selecting the communication having higher signal quality. Interface protection is provided through a protection transceiver thus implementing M:N equipment protection and 1+1 optical protection.

Abstract: A switchless optical add/drop module (OADM) includes: a first variable optical splitter (VOS) for splitting a composite optical signal including a plurality of channels into a first portion and a second portion; a first multi-channel variable optical attenuator (MCVOA) optically coupled to the first VOS, where the first MCVOA blocks dropped channels of the first portion, transmits express channels of the first portion, and balances power levels of each of the transmitted express channels of the first portion; a second VOS optically coupled to the first MCVOA opposite to the first VOS for combining the transmitted express channels of the first portion and added channels; and a second MCVOA optically coupled to the first VOS, where the second MCVOA blocks express channels of the second portion, transmits dropped channels of the second portion, and balances power levels of each of the transmitted dropped channels of the second portion.

Abstract: A flexible open ring optical network includes a plurality of nodes connected by twin or other suitable optical rings. Each node is operable to passively add and passively drop traffic from the rings. The nodes may include a transport element for each ring. The transport elements include an optical splitter element and an optical combiner element. The optical splitter element is operable to passively combine an add signal including local add traffic and a first transport signal including ingress traffic from a coupled optical ring to generate a second transport signal including egress traffic for transmission on the coupled optical ring. The optical combiner element is coupled to the optical splitter element and is operable to passively split a third transport signal including the ingress traffic to generate a drop signal including local drop traffic and a fourth transport signal including the ingress traffic.

Abstract: A bidirectional optical add-drop multiplexer adds and drops optical signals having specific wavelengths among the WDM optical signals transmitted bidirectionally through one of the optical transmission lines connected between neighbor nodes in a bidirectional WDM ring network.

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 column, 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: Disclosed is a bidirectional optical add/drop multiplexer that includes a first filter for reflecting a first optical signal pre-selected among input forward optical signals and transmitting the remaining forward optical signals, a second filter for reflecting a second optical signal pre-selected among input reverse optical signals and transmitting the remaining reverse optical signals, a first optical splitter for combining the first optical signal and the forward optical signals by reflection from the first filter, wherein the reflected second optical signal having passed through the first filter is outputted to a connected second drop terminal and the first optical signal input from a connected first add terminal is outputted to the first filter, and a second optical splitter for adding the second optical signal and the reverse optical signals by reflection from the second filter, wherein the reflected first optical signal having passed through the second filter is outputted to a connected first drop termi

Abstract: An optical multiplexing device includes an optical element having at least one set of diffractive elements, and an optical reflector. The reflector routes, between first and second optical ports, that portion of an optical signal transmitted by the diffractive element set. The diffractive element set routes, between first and multiplexing optical ports, a portion of the optical signal that is diffracted by the diffractive element set. More complex optical multiplexing functionality(ies) may be achieved using additional sets of diffractive elements, in a common optical element (and possibly overlaid) or in separate optical elements with multiple reflectors. Separate multiplexing devices may be assembled with coupled ports for forming more complex devices. The respective portions of an optical signal transmitted by and reflected/diffracted from the diffractive element set typically differ spectrally.

Abstract: The present invention relates to a network node that includes optical add/drop modules such that a module can be exchanged without disruption of the connections.

Abstract: A method and system producing and transmitting pulsed or continuous wave signals through one or more optical fibers to a plurality of remote sensors provided in a hostile environment. The produced signals transmitted along one of the optical fibers would be demultiplexed and transmitted to separate sensors. The sensors would then modulate these signals which would then be combined onto a single output optical fiber which is to be analyzed. A spectrometer or other signal processing device, generally included in a shielded environment, would be utilized to process the modulated signals.

Abstract: A re-configurable optical add/drop apparatus separates an optical input signal into a first signal having a plurality of channels and a second signal having a plurality of channels and includes a channel router with drop ports, a wavelength-selective channel attenuator with a controllable polarization modulator, and an optical coupler. The channel router routes the selected channels of the first signal to the drop ports. The wavelength-selective channel attenuator selectively blocks some of the channels of the second signal to produce a third signal. The optical coupler couples the third signal with a fourth signal having a plurality of add channels to produce an optical output signal.

Abstract: A broadcast and select ring network for optical WDM communication includes two parallel fiber rings (1a, 1b) carrying traffic in opposite directions between nodes (3; A, B, C, D). The nodes comprise on their receive side selecting means such as a cross connect device (21) or similar means allowing a flexible selection of the wavelength channels which are to be received by each node. Thereby, any WDM channel in the rings can be selected and received in the nodes. For example, all nodes can receive signals in the same channel for e.g. set up or reconfiguration purposes. Furthermore, the number of receivers in a node can be small but still all channels can be received. The number of transmitters in each a node can also be small since every transmitter can reach every receiver.

Abstract: A protection arrangement for an optical switching system includes protection switching for switch planes in the optical core and for ports in the tributary cards. For a multiple layer switch core protection is also provided between layers. A first layer is for switching optical channels. The protection switches used may be 1×N, 2×N or 3×N MEMS optical switches. The 1×N MEMS provides for protection switching. The 2×N MEMS provides protection switching and testing capability. The 3×N MEMS provides for protection switching, testing and backup of the protection switching. Application of these protection switches is shown in lambda plane switch cores, multiple layer switch cores and combined switch cores.

Abstract: In an optical grating device, a grating arrangement receives different wavelength output signals from a plurality of radiation sources at input ports thereof, and generates therefrom a multiplexed wavelength output signal at a zero diffraction order output port of the grating arrangement. Additionally, the gating arrangement generates at least one predetermined wavelength output signal at one of a group consisting of a separate predetermined location in an at least one of a symmetric non-zero diffraction order of the grating arrangement, within the grating arrangement itself, and a combination thereof. A separate power tap is coupled to detect the power of a separate one of the at least one predetermined wavelength output signal from the grating arrangement.

Abstract: Techniques for providing normal operation and service restoration capability in the event of failure of terminal equipment or transmission media in a heterogeneous network, such as a hybrid network containing single- and multi-wavelength lightwave communications systems. An optical switching node (OSN) is placed at each node in the ring network to provide the required connections between various fibers and terminal equipment, but having switch states that allow signals on the protection fibers to bypass the terminal equipment at that node. Ring-switched signals propagate around the ring on protection fibers without encountering the terminal equipment at the intervening nodes. To the extent that the protection fiber links between any given pair of nodes are incapable of supporting all the relevant communication regimes, such links are modified to provide such support.

Abstract: The first present invention provides an optical switch including the following elements. At least a plurality of optical transmission lines are provided for transmissions of optical signals. Each of the at least plurality of optical transmission lines have at least an impurity doped fiber. At least an excitation light source is provided for emitting an excitation light.

Abstract: Optical systems are provided. A representative optical system includes an optical transceiver with an optical source and an optical receiver. The system also includes an optical waveguide. At least one of the optical source and the optical receiver is optically coupled to an intermediate portion of the optical waveguide. The optical source provides optical signals for propagation by the optical waveguide, and the optical receiver receives optical signals propagated by the optical waveguide. Methods, optical transceivers and other systems also are provided.

Abstract: An optical network includes an optical ring and a plurality of add/drop nodes coupled to the optical ring. Each of the add/drop nodes is operable to passively add and drop one or more traffic streams to and from the optical ring, and each traffic stream comprises a channel. A hub node also coupled to the optical ring is operable to selectively pass and terminate individual traffic streams.

Abstract: A reconfigurable optical add-drop multiplexer is disclosed including an optical splitter receiving an input optical signal and splitting the input optical signal into a dropped optical signal and an express optical signal; a wavelength blocker optically coupled to the optical splitter, the wavelength blocker blocking particular wavelengths in the express optical signal; a cassette having a plurality of slots capable of accepting a plurality of pluggable optical filters; at least one pluggable optical filter optically coupled to the optical splitter, the pluggable optical filter filtering wavelengths so as to output a particular wavelength channel from the dropped optical signal; and an optical combiner optically coupled to the wavelength blocker and to an optical add path on which an optical add signal may be carried, the optical combiner combining the express optical signal having particular wavelengths expressed by the wavelength blocker and the optical add signal.

Abstract: Agile OADM structures having a range of tradeoffs between costs and flexibility are disclosed. In certain implementations, cyclic AWGs (arrayed waveguide gratings) are employed. Excellent optical performance is achieved along with relatively low initial and upgrade costs. An economically optimal level of network flexibility may thus be achieved.

Abstract: A multi-channel optical switching system particularly usable as a programmable optical add/drop multiplexer (POADM) in a multi-wavelength communication system. The switching system uses a thin film optical demux/mux 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 connected to the thin film optical demux/mux and a selecting device to select which optical channel is directed to which of the optical ports.

Abstract: An optical signal transmitter is disclosed that transmits an optical signal with corresponding Wavelength Division Multiplexing (WDM) channels and Time Division Multiplexing (TDM) channels. The transmitter is comprised of a laser, a dispersion system, and a modulator. The laser generates and transmits a narrow laser pulse comprised of a plurality of wavelength channels. The dispersion system broadens the narrow laser pulse into a wide laser pulse. The modulator modulates the wide laser pulse based on an electric modulation signal comprised of a plurality of time slot channels wherein the time slot channels in the electric modulation signal correspond to the wavelength channels in the wide laser pulse respectively. The modulator transfers a modulated wide laser pulse. Channels of the modulated wide laser pulse are hybrid wavelength and time slot channels. The transmitter singularly transmits a WDM optical signal comprised of multiple wavelength channels.

Abstract: A data link system comprising a shelter housing sensitive radio frequency equipment and an antenna located apart from the shelter. A single fiber, bi-directional fiber optic link couples the antenna to the shelter. Both RF signals and data signals are sent across the data link.

Abstract: A single-sided optical switching device for functioning as a dual switch wherein individual switches share common switching means is disclosed. The individual switches have separate ports and share common switching means formed by a moveable refractor, a single lens and a stationary reflector, wherein the movable refractor is positionable between the lens and the stationary reflector for redirecting light within ports of individual switches. An embodiment of the device provides a single-sided dual 2×2 bypass switch comprising a single lens and a single switching element.

Abstract: A communication network is arranged in a ring configuration of network elements (12) coupled by working spans (16) associated protection spans (18), with multiple rings sharing network elements (12a and 12b). A shared protection span (18ab) is coupled between pairs of shared network elements (12a and 12b). A matrix 28 in a shared network element (12a or 12b) can couple any channel from one of the incoming working spans or protection spans to any channel of the shared protection span (18ab).

Abstract: An optical delay circuit includes a plurality of defect waveguides arranged in parallel and including a line-shaped defect in a periodic refractive-index distribution structure of a photonic crystal. The defect waveguides include a multiplexing/demultiplexing portion in which the defect waveguides are arranged close to each other to multiplex and demultiplex light; and an optical delay portion extending from the multiplexing/demultiplexing portion, in which the defect waveguides are arranged with a predetermined distance therebetween so that light propagating in any of the defect waveguides does not interfere with light propagating in the other defect waveguides. Each of the waveguides has a different configuration.

Abstract: A node for an optical network includes a demultiplexer operable to separate an ingress wavelength division multiplexed (WDM) signal into a plurality of ingress channels. An ingress amplifier array is coupled to the demultiplexer and includes a plurality of channel amplifiers. The channel amplifiers are each operable to independently amplify one of the ingress channels while maintaining a channel power variation between the channels within an operational limit of the network.

Abstract: A link based network protection path calculation mechanism wherein a protection route is calculated that is guaranteed not to traverse the link it is intended to protect. The mechanism takes advantage of the fact that the same color cannot pass twice through the same optical fiber. The protection path is determined by eliminating all colors from the logical topology of the network except for the color corresponding to the link to be protected before executing the search algorithm. This serves to guarantee that the protection path calculated will not traverse the same physical fiber as the link to be protected. Virtual colors can be assigned to the links running through fiber bundles such that they do not pass through the same fiber/bundle twice.

Abstract: A method and apparatus is provided for power balancing an optical signal wavelength to be added to an OADM having at least one drop port and at least one add port. The method begins by monitoring a power level of a first signal wavelength being dropped on the drop port and a power level of a second signal wavelength being added on the add port. The power level of the first signal wavelength is compared to the power level of the second signal wavelength. Based on the step of comparing, the optical attenuation is adjusted along the add port so that the power level of the second signal wavelength becomes substantially equal to the power level of the first signal wavelength.

Abstract: An optical transmission system which permits transmission distance to be prolonged without using repeaters and yet ensures economical, high-quality optical transmission. A branch station performs non-repeated communication with an optical branching point and includes a light pumping section for causing pump light to enter an optical fiber through which a branched, receiving optical signal flows, to perform optical amplification by using the fiber as an amplification medium. An optical branching device includes an optical amplification section and an optical branching section. The optical amplification section redirects the pump light originated from the branch station and propagated through a line to the paired line through which an optical signal transmitted from the branch station flows, to excite an amplification medium inserted in the paired line and doped with active material for optical amplification and thereby amplify power of the optical signal transmitted from the branch station.

Abstract: A light branching/inserting apparatus which can easily control light signal wavelengths, and which can branch, insert or transmit light signals having an optional wavelength and optional multiplexed number, by using a wavelength selection filter utilizing acousto-optic effects.

Abstract: Disclosed herein is a signal transmission method in a wavelength-division-multiplex (WDM) transmission system. The WDM transmission system comprises a first WDM terminal for transmitting a WDM signal, a second WDM terminal for receiving the WDM signal, and an optical add-drop multiplexer (OADM) node for transmitting to a network element an optical signal of a specific wavelength of the WDM signal which is transmitted between the first and second WDM terminals. The WDM signal is transmitted from the first WDM terminal to the second WDM terminal regardless of whether an optical signal is added or dropped at the OADM node. The network element employs an optical signal of an idle wavelength of the WDM signal that has no transmission data, to transmit another transmission data that is transmitted by the network element.

Abstract: In one aspect of the invention, an apparatus operable to facilitate add/drop multiplexing of optical signals includes an input operable to receive an input optical signal and an added optical signal, the input operable to generate a first and a second copy of the input signal and a first and a second copy of the added signal. The apparatus further includes a plurality of at least substantially reflective surfaces, each operable to receive either the first signal copies or the second signal copies and to reflect the copies for ultimate combination at an output to form an output signal for transmission. At least one of the at least substantially reflective surfaces comprises a moveable mirror operable to change its position relative to the input to create a phase shift between the first and second signal copies so that either the input optical signal or the added optical signal is communicated as the output signal depending on the position of the at least one moveable mirror.

Abstract: A re-configurable optical add-drop multiplexer (OADM) (800) includes a first optical circulator (10), a second optical circulator (30), and a fiber Bragg grating (FBG) (20). The first optical circulator has a first circulator port (11), a second circulator port (12), and a third circulator port (13). The second optical circulator has the same structure as the first optical circulator. The FBG has a first state where it reflects an optical signal with a particular wavelength and passes all other wavelengths, and a second state where all the optical signals pass through it. The signal of the particular wavelength can thus be dropped from the optical signals by reflection of the FBG and output from the third circulator port of the first optical circulator, and a new signal of the same dropped wavelength can be added into the optical signals through a first circulator port (31) of the second optical circulator.

Abstract: A system for matching a optical filter characteristic of a first filter tunable in wavelength with an optical first signal comprises a modulator for modulating at least a part of the first signal with a modulation signal before being applied to the first filter. An analyzing unit derives a control signal for tuning the first filter by analyzing the modulated first signal after passing the first filter in conjunction with the modulation signal.

Abstract: A bidirectional WDM self-healing ring network is provided and includes an outer ring network and an inner network for processing N units of optical signals and for performing a protection switching by using the outer ring network when the inner ring network suffers a link failure.

Abstract: In a known wavelength multiplexer, optical signals to pass are passed with their wavelengths held identical. Therefore, unless an unused wavelength common to all zones exists in case of setting an optical channel, the channel cannot be set. According to the present invention, a drop/add type wavelength multiplexer includes a wavelength converting section (50 in FIG. 5) which converts the wavelengths of optical signals to pass from the input side of the multiplexer to the output side thereof. In a network employing the wavelength multiplexers at individual nodes, a new optical channel can be easily set by utilizing wavelengths not used at the nodes.

Abstract: A wavelength-selective routing capability is provided in a single network element by configuring the network element using a combination of add/drop network elements to route individual optical channels of WDM signals among a plurality of optical transmission paths coupled to the network element. Any optical channel of any WDM signal received at the network element can be selectively added, dropped, or routed among the multiple optical transmission paths within and external to the node.

Abstract: Optical systems and devices for processing spectral groups, and optical methods for forming spectral groups, the optical system including at least one sub-network including at least one spectral group router configurable to route a plurality of optical signal channels within a spectral group, when contained within said sub-network and terminate optical channels within a spectral group, when bounding said sub-network, each optical signal channel being transmitted from one node within said sub-network to another node in said sub-network.

Abstract: The virtually unused switching fabric of an OC-192 SONET transport node is used to greater effect when used as a switching node. Several of the nodes are used in the central office (CO) of a communication network. Each node terminates an optical network link and each node hosts a number of transport cards that also terminate different optical network links. The nodes provide space-switching between the cards. Additionally an intra-CO optical link is provided that interconnects the nodes to allow traffic flow between any of the optical network links in the CO that are terminated by transport cards or the nodes.

Abstract: Techniques for calibrating tunable optical devices using a probing signal as a reference so as to achieve an accurate control over an absolute wavelength of the tunable optical devices. A probing signal being a calibrated optical signal with a spectrum centered at a desired add/drop channel or wavelength is introduced into an N-port circulator coupled between two tunable optical devices. When the two tunable optical devices are tuned not exactly at the desired wavelength, a portion of probing signal will be reflected or dropped out by the two tunable optical devices. The dropped probing signal is detected and coupled to a signal processor or circuitry configured to generate adjustments to or the control signals for controlling the tunable optical devices in accordance with the reflected probing signal being maximized.

Abstract: A WDM bidirectional self-healing optical ring network is provided in which an outer ring network and an inner ring network can both handle N optical signals. The network includes a node; an optical add/drop multiplexer having a 1×N demultiplexer and a 1×N multiplexer; a pair of optical switching devices each connected to an optical fiber link intervening between the optical add/drop multiplexer and another node on the both ends of the optical add/drop multiplexer; and, a pair of circulators each connected between the optical add/drop multiplexer and a particular optical switching device in the optical switching device pair, each circulator having three ports, two of the three ports being connected to a corresponding optical switching device and remaining one port being connected to the optical add/drop multiplexer.

Abstract: An optical ring network architecture including a number (N) of multi-add/drop filters, such as filters formed using symmetrical pairs of frequency routers. Each multi-add/drop filter is coupled to two other multi-add/drop filters using N?2 transmission media, such as optical fibers, to form a ring. The network also includes a number (N) of terminal stations associated with the multi-add/drop filters. A terminal station (p) is coupled with, and receives information from, its associated multi-add/drop filter (p) through a single optical fiber. In addition, the terminal station p is coupled with, and transmits information in a first direction around the ring to, a multi-add/drop filter p+1 through a single optical fiber. Communications from terminal station p to each other terminal station in the first direction are assigned one of N?1 wavelengths such that no two wavelengths on a given optical fiber are associated with communications between terminal stations in the same direction.

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: An all optical network for optical signal traffic has at least a first ring with at least one transmitter and one receiver. The first ring includes a plurality of network nodes. At least a first add/drop broadband coupler is coupled to the first ring. The broadband coupler includes an add port and a drop port to add and drop wavelengths to and or from the first ring, a pass-through direction and an add/drop direction. The first add/drop broadband coupler is configured to minimize a pass-through loss in the first ring and is positioned on the first ring.

Abstract: An optical access network includes a first ring and a second ring communicating optical signals in opposite directions. The network also includes an access node coupled to both rings that adds traffic in a first wavelength of a first optical signal communicated on the first ring. Furthermore, the network includes a hub node coupled to each ring and coupled to an optical core network. The hub node receives the first optical signal, forwards a first copy of the signal to a first wavelength blocking unit that terminates the traffic in the first wavelength, and forwards a second copy of the signal to a first network interconnection element that forwards the traffic in the first wavelength to the core network. Furthermore, upon detection of an interruption of the traffic in the first wavelength on the first ring, the access node adds the traffic in a second wavelength of a second optical signal communicated on the second ring.

Abstract: A method and system for control signaling in an open ring optical network includes transmitting traffic in an optical ring. At each of a plurality of nodes along the ring, local traffic is passively added to and passively dropped from the connected ring. At each node, an ingress optical supervisory channel (OSC) signal is dropped from the ring to a managing element. An egress OSC signal is added to the ring from the managing element. The OSC signals may be in-band signal or out-of-band signals.