Abstract: An optical signal processing method and apparatus. The method includes: obtaining a first sending signal, where the first sending signal is a signal that is sent by a first transmitter to a second receiver through a first optical fiber; determining estimation information of a backward optical signal based on the first sending signal; the backward optical signal is generated during transmission of the first sending signal, the backward optical signal is transmitted through at least one fiber section in the first optical fiber, and a transmission direction of the backward optical signal is opposite to a transmission direction of the first sending signal; and obtaining a second sending signal based on the estimation information of the backward optical signal. According to the embodiments, impact of the backward optical signal on effective signal transmission can be reduced, and a signal-to-noise ratio can be improved.

Abstract: An optical network including a plurality of gateway nodes interconnected with a plurality of intermediate nodes with segments of fiber. The network includes a plurality of devices, such as reconfigurable optical add drop multiplexers, optimally placed at various nodes throughout the network. The device placement is optimized with an integer linear programming analysis considering span definition such that any given span involves some number of segments not exceeding a number of segments that would require wavelength regeneration, cost of placement of a device at a given node, cost of wavelength regeneration, and various parameters and constraints.

Abstract: Embodiment of present invention provide an optical subassembly that includes a first, a second, and a third band filter (BF) each having a common port (CP), a port-A (PA), and a port-B (PB). The PA of the second BF is connected to the PA of the third BF and the PB of the first BF is connected to the PB of the third BF. The optical subassembly is adapted to route a first optical signal of a blue band from the PA to the CP of the first BF; to route the first optical signal from the CP of the second BF to the CP of the third BF; to route a second optical signal of a red band from the CP of the third BF to the CP of the first BF; and to route the second optical signal from the CP to the PB of the second BF.

Abstract: The present disclosure relates to a modulator arrangement, including at least a first and a second electro-optical Mach-Zehnder modulator. At least one optical waveguide of the first Mach-Zehnder modulator crosses at least one optical waveguide of the second Mach-Zehnder modulator. A method for fabricating a modulator arrangement is also disclosed herein.

Abstract: Systems and methods include determining a current state of a network; determining a new state for the network having an improved cost relative to the current state; determining a defragmentation plan to move the network from the current state to the new state, the defragmentation plan including a sequence of steps; and, responsive to an event that presents an opportunity, implementing one or more steps of the sequence of steps. The implementing is conditioned on occurrence of the opportunity.

Abstract: Devices, computer-readable media and methods are disclosed for determining reachability for a wavelength connection in a telecommunication network. For example, a processor deployed in a telecommunication network may calculate a fiber loss on a link in the telecommunication network using optical power measurements and determine that a destination node of a wavelength connection is not reachable via a path that includes the link based upon the fiber loss of the link that is calculated. In one example, the determining is based upon a number of links in the path, an effective fiber loss for each link in the path, a penalty for nodes in the path, and an acceptable loss value. The processor may further perform a remedial action in response to determining that the destination node of the wavelength connection is not reachable via the path.

Abstract: When, in each of optical submarine relay apparatuses of the optical submarine cable system in which the optical submarine relay apparatus is arranged in each relay section of an optical submarine cable, a Laser Diode (LD) driving device for excitation (11) for outputting an excitation light to excite an optical amplifier is configured to include a plurality of LD driving circuits whose requiring currents are different from one another, which are, for example, a first LD driving circuit (111a) of a required current Ia and a second LD driving circuit (111b) of a required current (Ib) therein, a power feeding line for feeing power to the first LD driving circuit (111a) and a power feeding line for feeing power to the second LD driving circuit (111b) are configured to be connected in parallel to each other.

Abstract: Systems and methods include determining a defragmentation plan that changes a configuration of a network to move the network from a current state of operation to a new state of operation; updating any of the defragmentation plan and the new state of operation in response to an opportunity presented during operation of the network; and implementing one or more steps in the defragmentation plan based on the opportunity. The opportunity can be anticipated to occur at a future time and implementation of the one or more steps is conditioned on occurrence of the opportunity. For example, the opportunity can include any of a maintenance window, a network equipment change, a capacity change in the network, a change to demand in the network, an external event including weather, and changes in links in the network. Also, the opportunity can include a fault.

Abstract: Devices, computer-readable media and methods are disclosed for determining reachability for a wavelength connection in a telecommunication network. For example, a processor deployed in a telecommunication network may calculate a fiber loss on a link in the telecommunication network using optical power measurements and determine that a destination node of a wavelength connection is not reachable via a path that includes the link based upon the fiber loss of the link that is calculated. In one example, the determining is based upon a number of links in the path, an effective fiber loss for each link in the path, a penalty for nodes in the path, and an acceptable loss value. The processor may further perform a remedial action in response to determining that the destination node of the wavelength connection is not reachable via the path.

Abstract: A touch screen display assembly can include a touch sensitive screen having a screen surface, and at least one hand anchor located adjacent the screen surface. The at least one hand anchor can also be configured to form a stabilizing feature when a user interacts with the touch sensitive screen.

Abstract: A controller for an optical network includes a network interface configured to communicate to one or more nodes in an optical network that includes a plurality of nodes interconnected by a plurality of links; a processor communicatively coupled to the network interface; and memory storing instructions that, when executed, cause the processor to obtain information related to a plurality of services that require spectrum assignment with each service given a time-constraint T for restoration to a restoration path and each service on its home route given a margin-constraint X dB for transients caused by restoring channels, classify each of the plurality of services in terms of viable paths in the optical network, restoration speed each viable path can tolerate, and re-tunability, and assign a home route and a restoration route, a restoration speed, and spectrum for each of the plurality of services based on priority.

Abstract: A multi-layer network planning system can determine a set of regenerator sites (“RSs”) that have been found to cover all paths among a set of nodes of an optical layer of a multi-layer network and can determine a set of candidate RSs in the optical layer for use by the links between a set of nodes of an upper layer, wherein each RS can be selected as a candidate RS for the links. The system can determine a binary path matrix for the links between the set of nodes of the upper layer. The system can determine a min-cost matrix that includes a plurality of min-cost paths. The system can determine a best RS from the set of candidate RSs and can move the best RS from the set of candidate RSs into the set of RSs for the links. The system can then update the binary path matrix.

Abstract: Aspects of an optical communications network are described that include two or more optical fibers arranged to allow communication in the same or in opposite directions. The optical network includes a first optical amplifier coupled to the first optical fiber, a second optical amplifier coupled to the second optical fiber, and an optical coupler that allows excess optical power from the first optical fiber to be provided for amplification of signals traversing the second optical fiber. The disclosed systems and devices thus enable excess power from one channel to be utilized to enable amplification of signals traveling on a different channel.

Abstract: Devices, computer-readable media and methods are disclosed for determining reachability for a wavelength connection in a telecommunication network. For example, a processor deployed in a telecommunication network may calculate a fiber loss on a link in the telecommunication network using optical power measurements and determine that a destination node of a wavelength connection is not reachable via a path that includes the link based upon the fiber loss of the link that is calculated. In one example, the determining is based upon a number of links in the path, an effective fiber loss for each link in the path, a penalty for nodes in the path, and an acceptable loss value. The processor may further perform a remedial action in response to determining that the destination node of the wavelength connection is not reachable via the path.

Abstract: A system for delivering optical power over an optical conduit includes at least one optical power source delivering multiple optical power forms, at least one of the optical power forms being a modulated optical power form. The system includes an optical power receiving device that is directly driven by the at least one modulated optical power form.

Abstract: Signal detection for optical transmitters in networks with optical combining. Presented herein is a multi-faceted means for performing electrical to optical conversion such as in an optical transmitter as implemented within a communication system including at least some optical communication links therein. The turning on and turning off of a light source (e.g., a laser diode (LD), a light emitting diode (LED), and/or other component that performs electrical to optical conversion) is performed in accordance with a number of operational parameters. Some communication systems include multiple optical links (e.g., multiple fiber-optic links) from multiple transmitters that connect to a common receiver. In addition, some optical transmitters include multiple electrical links (e.g., multiple electrical communication links) from multiple communication devices that connect thereto.

Abstract: For reducing and homogenizing an end-to-end delay of data packet transmissions in a large-scale wireless mesh network, a device, a system and a method are provided for controlling data packet transmission in the wireless network, wherein transmission parameters of an intermediate node are adjusted based on a distance between the intermediate node and a sender node.

Abstract: Provided are a passive optical network reach extender based on a wavelength tunable optical module and a method thereof. According to an embodiment of the invention, a passive optical network reach extender includes a first optical splitter configured to receive an optical signal from an optical line terminal and split the signal into optical signals having a multiplexed wavelength, a wavelength tunable remote relay configured to receive the optical signals split from the first optical splitter, and select and control an available wavelength for each port, a wavelength multiplexer configured to multiplex a wavelength of the optical signal output from the wavelength tunable remote relay, and a second optical splitter configured to split the optical signal multiplexed by the wavelength multiplexer into a plurality of optical network units.

Abstract: A computer system and method for transmitting LAN signals over transport systems. LAN signals are generated in any client LAN compliant interface. A transceiver receives the client LAN signal in the LAN format. The client LAN signals are not converted to a SONET transmission format at any time before reaching the transceiver. The transceiver then converts the client LAN signal to an internal electrical LAN signal before re-clocking the internal electrical LAN signal. The re-clocked internal electrical LAN signal is then re-modulated into a second LAN signal. The second LAN signal is then transmitted to a transport system.

Abstract: Disclosed are a phase locked loop (PLL) of a digital scheme and a method thereof. More specifically, disclosed are a digital phase locked loop having a time-to-digital converter (TDC), a digital loop filter (DLF), and a digitally controlled oscillator (DCO), and that is designed to have a constant jitter characteristic at all times even though an operating condition of a circuit varies according to a process, voltage, temperature (PVT) change, and a method thereof.

Abstract: All-optical phase-modulated data signal regenerator apparatus (10) comprising an optical input (12), an optical signal converter (16), an optical carrier signal source (18), optical signal forming apparatus (20) and an optical output (14). The input (12) is arranged to receive a phase-modulated optical data signal. The signal converter (16) is arranged to receive the data signal and to convert phase modulation of the data signal into a corresponding intensity modulation of an intermediate optical signal. The carrier signal source (18) provides an optical carrier signal.

Abstract: There is provided a repeater to relay an optical signal transmitted/received between an optical line terminal (OLT) and at least one optical network unit (ONU), the repeater including: a first port configured to receive an optical signal input from the at least one ONU; a converter circuit configured to convert an optical signal of a first transmission rate into an optical signal of a second transmission rate higher than the first transmission rate, the optical signal of the first transmission rate to be converted being included in optical signals received at the first port; and a second port configured to output the optical signal converted by the converter circuit to the OLT.

Abstract: A free space optical communication system (100) and method including: several optical beam expanders (414) for receiving incoming optical signals from ground sites and neighboring satellites; several optical preamplifiers (412) for preamplifying the received optical signals; one or more optical main amplifiers (404) for amplifying the preamplified optical signals; and an optical switch (408) for directing respective amplified optical signals to respective destinations via a respective optical beam expander. The respective amplified optical signals are inputted to a respective optical beam expander (414) for transmission to said respective destinations, as outgoing optical signals.

Abstract: An optical network architecture can include a first pair of tapered mixing rods and a second pair of tapered mixing rods. The optical network architecture can also include a first plurality of plastic optical fibers communicatively coupled from the first pair of tapered mixing rods to a first plurality of line replaceable units and a second plurality of plastic optical fibers communicatively coupled from the second pair of tapered mixing rods to a second plurality of line replaceable units. The optical network architecture can also include at least one plastic optical fiber communicatively coupled from the first pair of tapered mixing rods to the second pair of tapered mixing rods.

Abstract: The path selection and wavelength assignment to a selected path are performed by mapping the wavelength reach to the demand distribution (agile reach) resulting in a 50-60% increase in the network reach. The network reach is further increased (about 2.2 times) when on-line measured performance data are used for path selection and wavelength assignment. The connections may be engineered/upgraded individually, by optimizing the parameters of the entire path or of a regenerator section of the respective path. The upgrades include changing the wavelength, adjusting the parameters of the regenerator section, controlling the launch powers, mapping a certain transmitter and/or receiver to the respective wavelength, selecting the wavelengths on a certain link so as to reduce cross-talk, increasing wavelength spacing, etc.

Abstract: A free space optical communication system (100) and method including a constellation of several satellites (102). Each of satellites including: several inter-satellite optical telescopes (204) for optical communication with multiple neighboring satellites, each inter-satellite optical telescope is capable of adjusting its elevation angle; and several up/down link optical telescopes (206) for optical communication with multiple ground sites. As the constellation passes a given ground site, some of the up/down-link telescopes of a given satellite are configured to track at least two respective ground optical telescopes of the given ground site and send data to the ground optical telescope with the clearest line of sight to the given satellite. Moreover, each of the satellites includes optical circuitry (208, 210, 212, 216) for optically processing and switching incoming and outgoing optical signals without converting the optical signals into electrical signals.

Abstract: A method for regenerating and amplifying optical signals includes determining a source optical signal, adding a first pump optical signal and a second pump optical signal to the source optical signal to yield an intermediate optical signal, duplicating the intermediate optical signal to yield a first duplicate signal and a second duplicate signal, phase-shifting the first duplicate signal, passing the phase-shifted first duplicate signal and the second duplicate signal bi-directionally through a nonlinear optical element, and performing degenerate phase-sensitive amplification on the phase-shifted first duplicate signal and the second duplicate signal.

Abstract: A method for regenerating optical signal includes determining a source optical signal to be regenerated, adding a first pump optical signal and a second pump optical signal to the source optical signal to yield an intermediate optical signal, creating a first conjugate optical signal and a second conjugate optical signal from the intermediate optical signal, and performing degenerate phase-sensitive amplification utilizing the first conjugate optical signal, the second conjugate optical signal and the source optical signal to yield an output optical signal. The source optical signal is modulated with a multilevel modulation format. Each conjugate optical signal has a phase that is a conjugate of a multiple of the phase of the source optical signal.

Abstract: Optical regenerators and amplifiers are expensive to implement and maintain. A method or corresponding apparatus in an example embodiment of the present invention relates to an optical planning tool that plans an optical network configuration by determining a plurality of costs for maintaining signal strength in corresponding network configurations including (i) a configuration of regenerators, (ii) a configuration of pre-or post-amplifiers, and (iii) a configuration of pre- and post-amplifiers in candidate locations and regenerator modules. The candidate locations for placing pre-or post-amplifiers are determined based on loss in each span, expected traffic patterns, and proposed regeneration locations along paths of expected traffic. The regeneration modules are located in locations determined based on the candidate locations. The example embodiment selects a configuration from among the network configurations as a function of the plurality of costs, helping reduce the cost of network deployment.

Abstract: In accordance with the present disclosure, disadvantages and problems associated with transmitting high capacity (e.g., 400 G) optical signals may be reduced. In accordance with an embodiment of the present disclosure a method for regenerating an optical signal comprises receiving an optical signal at a network element and measuring a performance characteristic of the optical signal. The method further comprises determining that the optical signal needs regeneration based on the performance characteristic of the optical signal. The method additionally comprises performing signal regeneration of the optical signal based on the determination that the optical signal needs regeneration.

Abstract: The present invention provides an optical networking device for re-amplifying, re-shaping, and re-timing an optical signal, as well as providing distortion compensation and performance monitoring of the optical signal. The optical networking device includes an all-optical regenerator device for one or more of re-amplifying, re-shaping, and re-timing the optical signal; a distortion compensator device for compensating for distortion associated with the optical signal; and a quality-of-signal monitoring device for measuring the quality of the optical signal. Preferably, the all-optical regenerator device, the distortion compensator device, and the quality-of-signal monitoring device are disposed within a single module. The quality-of-signal monitoring device measures the optical signal subsequent to distortion compensation. Alternatively, the quality-of-signal monitoring device measures the optical signal subsequent to distortion compensation and all-optical regeneration.

Abstract: A network component comprising at least one processor configured to implement a method comprising obtaining a wavelength availability information for a path, determining whether to implement a wavelength assignment based on the wavelength availability information, updating the wavelength availability information when the wavelength assignment is to be implemented, and forwarding the wavelength availability information. Also included is a method comprising obtaining a wavelength availability information, comparing a number of wavelengths in the wavelength availability information to a threshold, determining whether to implement wavelength conversion along a path when the number of available wavelengths is less than or about equal to the threshold, and resetting the wavelength availability information when wavelength conversion is to be implemented.

Abstract: A single step routing and wavelength assignment method and system for automated provisioning of services on DWDM networks is presented. This novel single step solution automates design and assignment of services in DWDM networks. For an automated provisioning platform that can handle the routing and wavelength assignment in a single step, the solution avoids reconfiguration of existing services. It also takes into consideration practical aspects of DWDM transponder availability at termination sites and regeneration sites along the selected route. The methodology includes iterative computation of common channel sets to avoid multiple shortest path computations for each of the wavelengths.

Abstract: An optical transmission system is provided. The optical transmission system includes a user side optical repeater device (ORD), a central office side ORD, and wavelength multiplexing and wavelength de-multiplexing functions (MUX/DEMUX). The user side optical repeater device (ORD) is to be connected with a user side optical network unit (ONU), transmits data in two ways, and is used for wavelength division multiplexing (WDM). The central office side ORD is to be connected with a central office side optical line terminal (OLT), transmits data in two ways, and is used for WDM. The wavelength multiplexing and a wavelength de-multiplexing functions (MUX/DEMUX), are used for relaying between the user side ORD and the central office side ORD.

Abstract: Methods and apparatus for optical analog to digital conversion are disclosed. An optical signal is converted by mapping the optical analog signal onto a wavelength modulated optical beam, passing the mapped beam through interferometers to generate analog bit representation signals, and converting the analog bit representation signals into an optical digital signal. A photodiode receives an optical analog signal, a wavelength modulated laser coupled to the photodiode maps the optical analog signal to a wavelength modulated optical beam, interferometers produce an analog bit representation signal from the mapped wavelength modulated optical beam, and sample and threshold circuits corresponding to the interferometers produce a digital bit signal from the analog bit representation signal.

Abstract: A method for regenerating and amplifying optical signals includes determining a source optical signal, adding a first pump optical signal and a second pump optical signal to the source optical signal to yield an intermediate optical signal, duplicating the intermediate optical signal to yield a first duplicate signal and a second duplicate signal, phase-shifting the first duplicate signal, passing the phase-shifted first duplicate signal and the second duplicate signal bi-directionally through a nonlinear optical element, and performing degenerate phase-sensitive amplification on the phase-shifted first duplicate signal and the second duplicate signal.

Abstract: The present invention utilizes external synchronization to generate a completely standardized or functionally standardized optical transmission unit of level k (OTUk[V]) signal providing less jitter and wander build-up through a network of optical transport network (OTN) elements. This increases noise margins of transported signals and payloads. The present invention provides stratum-level synchronization utilizing a standards-based approach. In one embodiment of the present invention, rate adapters are included to provide m/n scaling of OTUk[V] signals to rates common in SONET and SDH synchronizers to provide line and loop distribution of timing through OTUk[V] signals. The present invention provides a choice of external synchronization sources including building integrated timing source (BITS), line, and loop timing sources. In another exemplary embodiment, the present invention provides multiple external references and automated timing protection switching for redundancy and reliability.

Abstract: An optical linear feedback circuit has an optical loop delay path (10) for recirculating a sequence of optical signals, and an output path for outputting delayed optical signals after circulating one or more times around the loop. A selector (50) is provided for selecting one or more of the delayed optical signals from the sequence, and an optical logic circuit (20) is coupled to carry out a logical operation on the selected delayed optical signals to create an optical feedback signal which is coupled to the optical loop delay path, so that the optical feedback signal can be added to the sequence of optical signals already circulating. By recirculating around a loop, each round trip can be regarded as equivalent to a shift of a shift register, so longer sequences can be built up without needing an additional storage cell for each shift function.

Abstract: An apparatus comprising an optical power splitter, an optical delay line coupled to the optical power splitter, an optical amplifier (OA) coupled to the optical delay line, and an adaptive injection current (AIC) controller coupled to the optical power splitter and the OA. Also disclosed is an apparatus comprising at least one component configured to implement a method comprising converting an optical signal into a voltage signal, calculating an amplitude correction value for the voltage signal, inverting an amplitude of the voltage signal, adjusting the amplitude of the inverted voltage signal according to the amplitude correction value, and converting the adjusted voltage signal into a current signal. Included is a network comprising an optical line terminal (OLT) comprising an optical receiver and an AIC controlled OA coupled to the optical receiver, wherein the AIC controlled OA provides optical power equalization for any upstream optical signals.

Abstract: The invention provides an optoelectronic processing apparatus and methods for processing constraint information. The optoelectronic processing apparatus is applied to the optical transport network OTN device, and comprises: a 3R regeneration unit for reamplifying, reshaping and retiming a signal; a wavelength conversion unit for performing wavelength conversion to the signal; an interlayer adapting unit for converting the signal between the OCh layer and the ODUk layer; and a dispatching unit for dispatching the 3R regeneration unit, the wavelength conversion unit and the interlayer adapting unit according to a function identification parameter of the optoelectronic processing apparatus so as to process the signal. By the present invention, the management of the OTN device is simplified, and the 3R regeneration, wavelength conversion and optoelectronic interlayer adaptation information are managed uniformly.

Abstract: The invention relates to an optical fiber employable in an optical communication system using Raman amplification and adapted to improve OSNR and suppress bending loss at the same time, and the like. The optical fiber is a silica-based optical fiber having a depressed refractive index profile constituted by at least a core, an inner cladding having a low refractive index, and an outer cladding, an effective area Aeff of 110 ?m2 or more at the wavelength of 1550 nm, and a fiber cutoff wavelength ?c of 1.3 ?m or more but 1.53 ?m or less. The depressed refractive index profile is designed such that the ratio Ra(=2b/2a) of the diameter of the inner cladding to the diameter of the core is 2.5 or more but 3.5 or less and that the relative refractive index difference ?? of the inner cladding with respect to the outer cladding is at least the relative refractive index difference ??min where the bending loss at the wavelength for use is minimized but not exceeding (??min+0.06) %.

Abstract: A distribution node of a passive optical network (PON) comprises a first port for receiving a first optical continuous envelope modulated downstream data signal at a first wavelength (?C) from a first optical line termination unit (OLT1) and a second port for receiving a second optical continuous envelope modulated downstream data signal at a second wavelength (?L) from a second optical line termination unit (OLT2). A first converter (FBG-1) performs continuous envelope modulation-to-intensity modulation conversion of the first optical downstream data signal and forwards the converted first optical downstream data signal (?C) to the first group of optical network units (ONU1 . . . N). A second converter (FBG-2) performs continuous envelope modulation-to-intensity modulation conversion of the second optical downstream data signal and forwards the converted second optical downstream data signal (?L) to the second group of optical network units (ONUN+1 . . . 2N).

Abstract: A computer system and method for transmitting LAN signals over transport systems. LAN signals are generated in any client LAN compliant interface. A transceiver receives the client LAN signal in the LAN format. The client LAN signals are not converted to a SONET transmission format at any time before reaching the transceiver. The transceiver then converts the client LAN signal to an internal electrical LAN signal before re-clocking the internal electrical LAN signal. The re-clocked internal electrical LAN signal is then re-modulated into a second LAN signal. The second LAN signal is then transmitted to a transport system.

Abstract: An amplifier circuit in a PON and a method for using the same. The amplifier circuit may be used, for example in an ONU of the PON. In order to deal with varying customer requirements and the possibility of the ONUs or similar devices being installed at varying distances from the CO, a dynamically adjustable amplifier bias voltage is determined and applied to at least one amplifier in the amplifier circuit. The dynamic bias voltage is preferably a function of the input power to the ONU or the circuit output quality, or both. More than one dynamic bias voltage may be determined and applied in this fashion.

Abstract: A method for arranging relay stations in an optical transmission system including relay stations arranged so that optical signals at a first transmission speed can be transmitted from a transmission end to a reception end, includes: judging whether a transmission of optical signals at a second transmission speed different from the first transmission speed in a section connecting arbitrary two of the relay stations where a regenerative repeater station capable of regenerating optical signals can be arranged is possible; determining a combination of sections judged to be capable of performing transmission that enables a transmission of optical signals from the transmission end to the reception end; and making both ends of respective sections of the determined combination be the relay stations where the regenerative repeater station is arranged, wherein the judging includes a judgment condition which is satisfied in a section including sections but unsatisfied in one of the sections.

Abstract: An optical transmission system is described. The transmission system comprises a plurality of modules that include signal repeaters at each end. Within each module, optical signals are propagated between the repeaters through free space. Adjacent modules are connected by optical fibers to enable optical transmission therebetween. Adjacent modules are mechanically coupled with a flexible joint.

Abstract: A method is provided for all-optical regeneration of intensity modulated optical signals. A DFB laser diode is selected such that it has a gain bandwidth comprising the signal wavelength, the signal wavelength being outside the stopband of the DFB laser diode. Furthermore, the DFB laser diode is selected such that it can have a bistable amplification characteristic for the signal wavelength showing a hysteresis with an ascending branch and a descending branch, the ascending branch located at a higher input power level than the descending branch. The DFB laser diode is driven such that it operates in the bistable amplification regime, the descending branch of the hysteresis curve located at an input power level above the lower power level of the optical signal pulses and the ascending branch of the hysteresis curve located at an input power level below the upper power level of the optical signal pulses.

Abstract: An optical phase conjugator that can be deployed within a long-haul fiber-optic link of an optical WDM system to improve the system's tolerance to intra- and inter-channel nonlinear effects. In one embodiment, the optical phase conjugator has a digital signal processor configured to perform, in the digital electrical domain, a phase-conjugation transformation for various components of a WDM signal so that certain signal distortions imposed on that signal in the front portion of the fiber-optic link are reduced in the back portion of the link. Advantageously, the optical phase conjugator is flexibly configurable to employ an input-to-output carrier-frequency-mapping configuration that is most beneficial under particular operating conditions. mapping configuration that is most beneficial under particular operating conditions.

Abstract: The method of placing regenerators along a trail connecting a source network node with a destination network node of an automatically switched optical network first identifies N tentative regeneration sites and n+1 optical paths along the trail. Wavelengths are assigned to each optical path; and the performance of the trail is assessed based on regenerator placement data and wavelength assignment data. The data identifying this regenerator path, namely regenerator placement data, the wavelength assignment data and the performance parameter of the trail are stored in a list, if the performance parameter is over a threshold. Selection of the tentative sites is revised whenever the initial placement fails due to a reach problem, a wavelength-blocking problem or a path quality problem. If the time for revising the initial placement, or the cost of a regenerator path is unacceptable, the regenerator path is abandoned and a further placement is initiated.

Abstract: A method for regenerating optical signal includes determining a source optical signal to be regenerated, adding a first pump optical signal and a second pump optical signal to the source optical signal to yield an intermediate optical signal, creating a first conjugate optical signal and a second conjugate optical signal from the intermediate optical signal, and performing degenerate phase-sensitive amplification utilizing the first conjugate optical signal, the second conjugate optical signal and the source optical signal to yield an output optical signal. The source optical signal is modulated with a multilevel modulation format. Each conjugate optical signal has a phase that is a conjugate of a multiple of the phase of the source optical signal.