Abstract: A free space optical tap and multi/demultiplexer unit includes at least one optical unit that can tap off an optical signal from and/or add an input optical signal to a received FSO signal. The optical unit propagates the resulting optical signal, via free space, to a next optical unit of the system. The optical unit can include a holographic grating to diffract a portion of the received FSO signal to an optical detector and/or diffract an input optical signal to form part of a free space optical output signal. In addition, the FSO signal can include component signals of different wavelengths, with each optical unit of the system being wavelength specific to a different one of the wavelengths of the FSO signal.

Abstract: An input port of an add/drop node receives a plurality of optical channels. An add/drop port transmits a first drop channel of the plurality of channels when in a first channel mode and a second drop channel of the plurality of optical channels during a second channel mode. When the add/drop node is tuned from the first channel to the second channel, the output port transmits the plurality of channels spectrally located between the first channel and the second channel.

Abstract: A system and method for forwarding fault information in an optical network is disclosed. Responsive to a fault being detected at a node, the fault information is forwarded to the destination node in the form of a loss-of-signal condition by turning off laser transmitters used to propagate the signal towards its destination. Thus, a node or other network element not capable of generating an alarm signal consistent with an established alarm signaling protocol, such as a SONET alarm indication signal (AIS) or an SDH multiplexer section alarm indication signal MS-AIS, may still forward the fault condition to a downstream element.

Abstract: The present invention relates to a method using a node, a system comprising a node and a node for filtering signals in a wavelength division multiplexing (WDM) optical communications system, especially for re-configurably adding and dropping signals to and from an optical fibre path. The node comprising a drop filter, an add filter, a signal channel receiver, and a signal channel transmitter each being connected to a switch for signal channel relaying between said network, and signal channel dropping and adding from and to said network. The node provides low loss for relayed signals by allowing the drop filter to have a low crosstalk isolation, and provides high crosstalk isolation for dropped signal channels by connecting said receiver to the switch through an additional filter with high filtering characteristics for at least one predetermined signal channel of said signal.

Abstract: Disclosed herein is an optical add/drop device including an optical demultiplexer for separating WDM signal light into n optical signals where n is an integer not less than 2, n first optical switches to which the n optical signals output from the optical demultiplexer are supplied, respectively, a second optical switch for adding provided on the input side of the first optical switches, a third optical switch for dropping provided on the output side of the first optical switches, n regenerators for wavelength converting the optical signals passed through the first optical switches, and an optical multiplexer for wavelength division multiplexing the wavelength-converted optical signals. A transmission distance between nodes can be increased by using this device.

Abstract: In networks carrying existing optical traffic on one wavelength band in combination with wavelength division multiplexed traffic carried on a second wavelength band, there is a need to enable processing of the two systems without subjecting the WDM channels to unacceptable losses. The invention meets the above need by the provision of a node in an optical communications network that has a first set of add/drop filter elements for extracting and combining optical signals carried on wavelength division multiplexed channels in a first wavelength band and an extraction element and combining element for dropping and adding, respectively, a service channel associated with the wavelength division multiplexed channels. The extraction element is arranged upstream of the add/drop filter elements relative to the direction of traffic flow and the combining element is arranged downstream of the add/drop filter elements.

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: An optical network terminator for terminating and reducing the accumulated noise in optical networks, particularly ring based networks. The terminator eliminates problems of noise accumulation from amplifier spontaneous emission (ASE), thermal noise, etc., while providing bi-directional communications in the optical network. The optical network may have any topology including ring, star, mesh, point-to-point, etc. In the case of an optical ring, the ring is broken and an optical terminator is placed in line therewith. The optical network terminator includes a filer such as an optical demultiplexer/multiplexer or Fiber Bragg Grating (FBG) based filter. Each individual wavelength of light is filtered and a multi-wavelength optical output is generated whereby the noise accumulation is removed. Each channel is adapted to only pass a band-limited signal around the center frequency corresponding to the wavelengths supported by the particular optical ring network.

Abstract: A bit-rate-transparent electrical space-division switching matrix is employed in an optical cross-connect and the input/output stage is constructed from simple, broadband optical receivers and transmitters. Since the switching matrix operates in unclocked manner, i.e. its switching function is not based on internal bit timing and frame timing, arbitrary signals can be switched though transparently at almost any bit rate, independently of the protocol-type being used. The inputs and outputs likewise operate fully independently of bit rate and protocol, since they only implement an O/E conversion or O/E conversion. By virtue of this structure, a simply constructed but extremely powerful optical cross-connect is created that can be employed equally for all types of optical signals within the stipulated wavelength-range.

Abstract: A communication system includes a plurality of nodes and a plurality of point-to-point links that interconnect the plurality of nodes into a network. Each node includes an optical switch to controllably route a plurality of in-ports of the optical switch into a plurality of out-ports of the optical switch. Each point-to-point link includes a free space optical channel. A first free space optical channel couples to a first node through a receive path and through a transmit path. The receive path couples to a respective in-port of the optical switch of the first node, and the transmit path couples to a respective out-port of the optical switch of the first node. In an alternative embodiment, a communication hub includes a plurality of neighborhood links to corresponding users, an optical switch coupled to the plurality of neighborhood links, and a trunk coupled between the optical switch and a free space optical channel link to the network.

Abstract: Disclosed herein is a bidirectional wavelength division multiplexed self-healing ring network. The ring network includes a central office and a plurality of remote nodes. Two optical fibers each connect the central office and the remote nodes in a ring form to allow optical signals to be bidirectionally received and transmitted between the central office and the remote nodes. One of the two optical fibers is a drop fiber for transmitting optical signals from the central office to the remote nodes, while the other is an add fiber for transmitting optical signals from the remote nodes to the central office.

Abstract: An optical demultiplexer includes a first light bandpass filter that receives an input light beam at a first angle of incidence, passes a first light wavelength, and reflects a reflected beam, and a second light bandpass filter that receives the reflected beam at a second angle of incidence and passes a second light wavelength. A beam redirection element such as a reflective surface receives the reflected beam from the first light bandpass filter and redirects the reflected beam toward the second light bandpass filter at the second angle of incidence.

Abstract: A surface emitting semiconductor laser system having an outcoupling aperture on a central waveguide. At either end of the central waveguide are means for reflecting a plurality of different wavelengths of light such that multiple wavelengths are outcoupled through a single outcoupling aperture. Means are provided by which the different wavelengths can be independently modulated.

Abstract: An add/drop node for an optical network comprises a passive splitter to split an ingress signal from the network into a first ingress signal and a second ingress signal. A first amplified splitter stages module is operable to passively split and amplify the first ingress signal into a plurality of drop signals. A filter module is operable to filter the second ingress signal to provide a filtered pass-through signal. A second amplified splitter stages module is operable to passively combine a plurality of add signals into a combined add signal and to combine the combined add signal with the filtered pass-through signal to create an egress signal forwardable to the network.

Abstract: Optical transmitter/receivers for use in a DWDM systems are provided. Transmission of data signals in a quadrature-return-to-zero (QRZ) format achieves a data transmission rate equal to eight times a base data rate, i.e., 80 Gbps over a 100 GHz channel if the base data rate is 10 Gbps, with high non-linear performance by setting the polarization state of the data bands such that non-linear effects induced by PMD are reduced. Additionally, a transmitter achieves a transmission data rate equal to 16 times the base data rate by sharpening the QRZ pulses and interleaving pulse-sharpened QRZ data signals in the time domain, further doubling the data rate. Using counterpropagation in the transmitter, carrier signals and data signals traverse the same length of fiber, reducing fringing effects in the transmitter. Related techniques enhance reception and detection of data at high data rates. A local pulse-sharpened carrier is mixed with a QRZ data signal at a detector reducing amplification noise by a factor of two.

Abstract: A system and apparatus for dropping and adding optical data streams in an optical communication network uses a photonic switching fabric for dropping but not adding optical data streams, and uses a combiner external to this photonic switching fabric for combining passed optical data streams from the photonic switching fabric together with added optical data streams. The added optical data streams are not limited to the wavelengths of the dropped optical data streams. The photonic switching fabric may be a Micro Electro Mechanical System (MEMS) that uses single-sided mirrors configurable to drop but not add optical data streams.

Abstract: The method and system for testing during operation of an open ring network includes opening a ring of the network at the node. Traffic circulating on the ring is dropped in the node to a monitoring element prior to or at the opening of the ring in the node. At the monitoring element, a signal received from the ring is tested. During tested and while the ring is open, traffic continues to be communicated between each node on at least one of the ring or a second ring each connecting the nodes of the network.

Abstract: The present invention provides an optical transponder with an add/drop operation function of optical channels, which combines operating functions of adding and dropping type optical transponders in accordance with mounting of a digital wrapper to simultaneously process two optical channels. The optical transponder receives an optical signal, converts the optical signal into electrical signal, adds maintenance information, monitoring information, and error correction information to each of the converted signals, and detects the maintenance information, monitoring information, and errors contained in each of the signals. Furthermore The optical transponder corrects the detected errors, and transmits the signals having the maintenance information, monitoring information, and error correction information and the signals of which errors are corrected.

Abstract: A reconfigurable optical add/drop module (ROADM) for dynamically adding or dropping various wavelengths of an optical signal without having to physically replace the module with a wavelength-specific add/drop module, and corresponding methods. A multiplexed optical signal in an optical network enters the reconfigurable optical add/drop module. Filters on the module separate various wavelengths of the optical signal along the module's various waveguides and a reconfigurable switching matrix directs the various wavelengths of the optical signal to be added, dropped and/or combined with other wavelengths.

Abstract: A 1:N protection scheme that provides both equipment and line protection against a single point of failure for a network hub situated in an optical ring network. The invention is suitable for use in DWDM based optical ring networks, and in particular, in networks constructed having a logical star over physical ring topology. The hub is modified to comprise N+1 transceivers, assuming an N channel DWDM network wherein each of the N transmitters operates using a different wavelength. Protection against line failures is achieved by optically splitting the transmit signal into two paths and transmitting each separately in opposite directions over the ring (i.e. 1+1 protection). In the event of a line failure, the other signal should still arrive at the destination. Protection against equipment failures is achieved through the use of a spare transceiver having a tunable wavelength of operation (i.e. 1:N protection).

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: This invention provides a new architecture for a communication system between head-ends and end-users which expands bandwidth and reliability of the communication system. A mux-node receives communication signals from a head-end and forwards the received communication signals to one or more mini-fiber nodes. The connection to the head-end is via a small number of optical fibers and the connections to each of the mini-fiber nodes may be via one or more optical fibers that may provide full duplex communication. The head-end may communicate with the mux-node using digital or digital and analog signals. The mini-fiber nodes may combine the signals received from the head-end with loop-back signals used for local media access control prior to forwarding the signals to the end-users. Upstream data are received by the mini-fiber nodes and transmitted to the mux-node.

Abstract: Provided is a millimeter wave oscillator for generating a high frequency signal required in wireless communication. The millimeter wave oscillator uses an overwritten fiber Bragg grating and a light detector such that two wavelengths in a certain phase relationship are produced to generate a signal of a millimeter wave band with a high frequency, whereby a light source is readily obtained without signal processing for phase lock.

Abstract: According to the present invention, a system and method provides for monitoring and controlling light propagation in optical transmission systems. The system either includes an optical circulator coupled to an optical add mechanism and is used to detect light propagation, or an optical monitoring device is coupled to the optical circulator and to the optical add device via a feedback path to control light propagation.

Abstract: An Optical Tapped Delay Line (OTDL) is combined with other known optical apparatuses to provide an add-drop multiplexer for a wavelength division multiplexing fiber optic network. Each output beam of the OTDL is spatially distinguishable in free space. This wavelength accessibility enables selection of one or more of the optical beams for adding or dropping. The system can be a fixed or tunable single channel add/drop system, a fixed or tunable multi-channel add/drop system, or a fully programmable add/drop system.

Abstract: A request method for performing optical power management to accomplish planned addition and removal of wavelengths in an optical communications system is disclosed, wherein each wavelength has a path of transmission through the system. The method comprises communicating a request for a power ramp to at least one path network component in the path, determining that the path network component has made preparations for the power ramp, and performing a power ramp in response to the determination. Further, a response method for performing power management to accomplish planned addition and removal of wavelengths in an optical communications system is disclosed, wherein each wavelength has a path of transmission through the system. The method comprises receiving a request for a power ramp, making preparations for the power ramp, determining that the power ramp has been completed, and resuming normal operation in response to the determination.

Abstract: A method and apparatus for assigning channel bands to a wavelength division multiplexed (WDM) system is disclosed. The WDM system includes an arrangement of optical amplifiers, banded optical add-drop multiplexers (OADMs) having blocking filters, and a tunable edge filter. The channel band assignment method suppresses amplified stimulated emissions (ASE) in a partially populated system in which at least one of the blocking filters is not in the transmission path. Channel bands are assigned from one edge of an amplified transmission window to the other in a sequential order and the tunable edge filter is adjusted to attenuate ASE wavelengths not blocked by the blocking filters as channels are assigned. A channel decommissioning method is also disclosed which employs similar techniques and the tunable edge filter to suppress ASE as blocking filters are removed or otherwise deselected from the transmission path.

Abstract: A wavelength division multiplexed (WDM) apparatus is provided for a bidirectional dense WDM optical fiber communication network with cost-effective and efficient allocation of the resources available at each network node. For each fiber link, the invention uses a WDM signal composed of channels propagating in opposite directions and a band optical add-drop multiplexer (OADM) to isolate or combine a band to the WDM signal spectrum. As a result, the invention significantly reduces the number fiber connections and filtering equipment required with respect to each direction of transmission.

Abstract: In a wavelength-division multiplexing system with an OADM, part of the chromatic dispersion on a transmission line is compensated for by a chromatic dispersion compensator for a dropped wavelength of the wavelength-division multiplexing system. Also, chromatic dispersion is compensated for by a chromatic dispersion compensator for an added wavelength of the wavelength-division multiplexing system. The chromatic dispersion compensator for dropped wavelength acts on the signal dropped by the OADM, and the chromatic dispersion compensator for added wavelength acts on the added signal. Both the chromatic dispersion compensators act on the passing signal. With the chromatic dispersion compensators being mounted in the optical transmission apparatus before the system is upgraded to OADM, it is not necessary to alter the chromatic dispersion compensating method and the variation of the communication quality can be suppressed.

Abstract: An optical fiber ring network includes a plurality of interconnected nodes, each pair of neighboring nodes being interconnected by a pair of optical links. Using coarse wavelength division multiplexing, data is transmitted in both directions over each link, using a first wavelength ?1 to transmit data in a first direction over the link and a second wavelength ?2 to transmit data in a second, opposite direction over the link. The two wavelengths ?1 and ?2 differ by at least 10 nm. Each of the data streams transmitted over the optical link has a bandwidth of at least 2.5 Gbps. Further, each data stream has at least two logical streams embedded therein. A link multiplexer at each node of the network includes one or more link cards for coupling the link multiplexer to client devices, and one or more multiplexer units for coupling the link multiplexer to the optical links.

Abstract: An amplifier including a first input for a first at least two input signals having mutually distinct wavelengths, a first output for a first at least two output signals, the first at least two output signals having said mutually distinct wavelengths, a first circulator including an input port coupled to the first input, an output port coupled to the first output, and an intermediate port coupled to a first end of a selective reflection circuit, and, a second circulator including an intermediate port coupled to a second end of the selective reflection circuit, an output port coupled to a first selective splitter, and an input port coupled to a second selective splitter, wherein the first selective splitter and the second selective splitter are centered about a first selected wavelength amongst the mutually distinct wavelengths.

Abstract: The instant invention provides an add/drop device including a wavelength filter, a quarter waveplate disposed on either side of the wavelength filter, and a polarizing beamsplitter disposed on either side of the quarter waveplates. Each polarizing beamsplitter has an input port and an output port for launching and receiving a beam of light having a known polarization. A polarization switch is optically coupled to each input/output port for selectably rotating the polarization of the input/output beams of light. Advantageously, the polarization switches, which work in cooperation with each other and the polarizing beam splitters, provide means for a non-moving parts add/drop device.

Abstract: An optical add-drop multiplexer successively comprises a first ferrule, a first graded index (GRIN) lens with a bandpass filter attached thereon, an optical crystal, a second GRIN lens, and a second ferrule. An input and an output optical fiber are stationed in the first ferrule, and a dropping and an adding optical fiber are stationed in the second ferrule. An optical multiplexed signal from the input optical fiber is transmitted through the first GRIN lens to the bandpass filter. From the bandpass filter, an optical signal having a wavelength identical to a central wavelength of the bandpass filter is output to the dropping optical fiber, and other optical signals having other wavelengths are coupled with an optical signal from the adding optical fiber having a wavelength identical to the central wavelength of the bandpass filter and are transmitted to the output optical fiber.

Abstract: A method and a system in which selected wavelengths of a wavelength division multiplexed (WDM) signal are modulated with multicast data for multicasting data services on an optical network. The WDM signal is received from a hub node of the optical network, such as a unidirectional ring network or a bi-directional ring network. A four-port wavelength crossbar switch (4WCS) selectably switches selected wavelengths from the optical network to a modulator loop. The modulator loop includes a multicast modulator that modulates the selected plurality of wavelengths with the multicast data. Each modulated wavelength is then switched back to the optical network by the 4WCS switch, and sent to a plurality of subscriber nodes of the optical network. This architecture allows a facility provider to be physically separated from a content provider, and affords the flexibility of selectively delivering multicast content to individual subscribers.

Abstract: A wavelength selective switch is realized by combining a quantized dispersion element and an array of switching means. The quantized dispersion element enables to concentrate all the wavelengths within predetermined wavelength bands onto the same location in the switching array. With this arrangement, a low fill factor switching array can be used while maintaining good flat-top spectral performance with no spectral dips and improving alignment tolerances.

Abstract: The invention proposes a Grouped Optical Add Drop Multiplexer (GOADM) comprising a periodic filter for forming a group of spaced optical wavelengths to be dropped or added.

Abstract: An exemplary embodiment of the invention is a communications device for use in a communications network. The communications device includes a plurality of interface ports, each of the interface ports receiving a first signal in a first format. A processor is coupled to the interface ports and receives the first signals. The processor provisions an overhead byte associated with one of the first signals and multiplexes the first signals to generate a multiplexed signal. A framer receives the multiplexed signal and the provisioned overhead byte and places the multiplexed signal in a second format to provide a second signal for transmission on the communications network.

Abstract: A wavelength blocker including an input port for launching an input beam of light, first dispersing means for dispersing the input beam of light according to wavelength, an array of independently addressable elements for selectively blocking a portion of the dispersed beam of light, second dispersing means for receiving the passed dispersed beam of light and for producing a single multiplexed beam of light therefrom, and an output port for transmitting a modified output beam of light. The array of independently addressable elements are designed such that the wavelength blocker is capable of blocking a variable number of non-consecutive channels without significantly affecting the unblocked channels.

Abstract: A self-adjusting optical add-drop multiplexer monitors the power in a drop signal and attenuates the power in an add signal to match the power in express WDM channels (signals). When used in a fiber network, and more particularly, in a metro network, the deleterious effects of optical amplification are reduced. Power attenuation is also used in an optical switching assembly particularly useful in two-fiber ring network. The optical switching assembly monitors drop channels from the two rings of the network and attenuates the add channel(s) accordingly. An optical switch operates to direct the drop signal from one of the two rings to a receiver in accordance with a control signal based on the monitored drop channels. The self-adjusting optical add-drop multiplexer also monitors the power in the drop signals and issues an alarm if the drop signal is of a power level above or below predetermined levels.

Abstract: A receiver transponder that is implemented in an optical add/drop multiplexer (OADM) is disclosed. The OADM is used in short haul type networks and receives light signals from two opposite directions on input fibers (21, 23). The optical input signals are converted to electrical signals by optical-to-electrical (O/E) converters (51, 53). The output terminals of the converters are connected to an electronic switch (61), which provides protection switching in a protected ring type network. The output signal of the switch can be monitored (65) before the signal enters a reshaping circuit (67), where the signal is reshaped, filtered from a supervisory channel, and adjusted to a proper drive level for a laser (69). The optical signal from the laser can travel a significant distance through a fiber (71) to a client receiver or sustain other forms of attenuation and still have sufficient signal power for reliable detection. An electrical output signal can be provided (73) by the reshaping circuit.

Abstract: The access node for optical networks with variable access wavelengths can be connected to user devices via respective first optical conductors and can be connected to the optical network via second optical conductors. The novel access node has light sources which emit at the wavelengths defined in the optical network. The light of the light sources can be modulated in the user devices. This prevents that in each case a light source which must be able to emit light of a different wavelength in a dynamic optical network or the wavelengths of which must be subsequently converted must be arranged in the individual user devices. In addition, it also prevents circuit boards leading to a high logistical expenditure having to be provided in the user devices. Accordingly, according to the invention, it is possible to construct the individual user devices without light sources. This considerably simplifies their construction and the method of use.

Abstract: An optical add-drop multiplexer comprises an optical switch (10) for selection of a desired wavelength channel to be extracted, a pre-processing channel assembly (20), an optical reflector (50), an optical extractor (60), a post-processing channel assembly (30), and an optical coupler (40) aligned with the post-processing channel assembly. The pre-processing channel assembly transmits a multiplexed signal stream containing a plurality of channels. The optical reflector directs light rays emitted from the pre-processing channel assembly into the optical extractor. The optical extractor comprises a narrow bandpass filter (62) that allows a desired channel to pass therethrough and reflects other unextracted channels. The desired channel can be dropped by switching to a corresponding output port of the optical switch. The optical reflector directs light rays reflected from the optical extractor to the post-processing channel assembly. The optical coupler combines the unextracted channels and an insertion channel.

Abstract: An optical add/drop multiplexer includes a multiplexing/demultiplexing unit having an input multiplexing port, an output multiplexing port and a plurality of demultiplexing ports each connected to a respective optical circulator. Each optical circulator includes a first port for internally inputting an added channel, a second port for outputting the added channel to a corresponding demultiplexing port and receiving a channel outputted by the corresponding demultiplexing port, and a third port for outputting the channel received from the second port.

Abstract: A system and method for a transparent WDM metro ring architecture in which optics enables simultaneous provisioning of dedicated wavelengths for high-end user terminals, while low-end user terminals share wavelengths on “virtual rings”. All wavelengths are sourced by the network and remotely modulated at customer “End Stations” by low cost semiconductor optical amplifiers, which also serve as transmission amplifiers. The transparent WDM metro ring architecture permits the communication of information and comprises a fiber optical feeder ring, at least one fiber optical distribution ring, a network node (NN), at least one access node (AN) said network node and said at least one access node connected via said fiber optical feeder ring and at least one end station (ES) connected via said fiber optical distribution ring to said at least one access node, wherein said user is attached to said at least one end station.

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 add/drop node of an optical WDN-network which has two fiber paths for light of a plurality of channels propagating in opposite directions comprises two add/drop modules (231, 23r) for each of the channels. All the modules are identically constructed. Each module comprises an add device (251, 25r) for adding light to one of the paths and a drop device (27r, 271) for deflecting a portion of light from a second one of the paths. A module comprises a house (41) enclosing the add device and the drop device. A first fixed connector (53, 73) is attached to the house for connection in the first path and to a an optical fiber (45, 65) which extends freely from the house and has a first free connector (43, 63) at its free end to be attached to the fixed connector of a neighboring add/drop module for continuing the first path through the considered add/drop module to the neighboring module.

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: A variable bandwidth hierarchical OADM apparatus and method handles different data rates, based on a waveband OADM and one or more wavelength OADMs in parallel. The wavelength OADM combines multiple adjacent channels with fine granularity up to the bandwidth of the waveband OADM. The wavebands and wavelengths to be passed, dropped, and added by the hierarchical OADM apparatus are all electronically selectable, hence no hardware modification is needed when the data rate is changed. The use of a coarse granularity waveband OADM and variable-bandwidth wavelength OADM with fine granularity enables our hierarchical OADM apparatus and method to provide a variable-bandwidth multi-granularity add/drop capability.

Abstract: Optical systems of the present invention include an electrical signal distortion compensator configured to electrically distort an electrical signal to offset optical distortion imposed by a Fabry-Perot filter on an optical signal corresponding to the electrical signal. The electrical signal distortion compensator can be used in an optical transmitter to distort the electrical signal prior to optical transmission, or in an optical receiver after optical transmission. The distortion compensation can be performed on a baseband signal or a modulated electrical carrier. Likewise, the distortion compensator can be deployed in combination with an optical receiver, which allows the use of the F-P filter-optical receiver combination with transmitters and receivers that do not include F-P filters or distortion compensators.

Abstract: A multi-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 connection that can be alternately used as a spare input connection.