Abstract: Systems and methods to reduce passband side-lobes associated with WSS-based ROADMs by applying a filter on each channel are provided. In an exemplary embodiment, a comb filter, such as a thin film filter or an interleaver, is utilized. Additionally, the present invention provides systems and methods to adaptively control amplifier target power and per wavelength target power to maintain signal launching power as per design in networks with WSS-based ROADMs. Accordingly, signal OSNR does not collapse faster than other similar configured system without WSS-based ROADM. In order to correct amplifier target power, the present invention utilizes system information about side-lobe size and OSNR at each amplifier.

Abstract: There is provided an optical network system in which optical signals modulated by each of at least two modulation methods are wavelength-division-multiplexed and transferred, including: an optical transmitter configured to transmit first optical signals modulated by each of at least two modulation methods; an add-drop multiplexer configured to drop second optical signals from wavelength-division-multiplexed optical signals transferred in the optical network system, and add the first optical signals to the wavelength-division-multiplexed optical signals; an optical receiver configured to demodulate the second optical signals corresponding to each of at least two modulation methods; and a controller configured to control wavelengths of the first optical signals, the second optical signals and the wavelength-division-multiplexed optical signals so as to rearrange wavelengths of the first optical signals, the second optical signals and the wavelength-division-multiplexed optical signals so that optical signals mo

Abstract: There is provided an optical receiving apparatus, including a receiver configured to perform coherent reception by mixing first light of a received optical signal and second light generated by a local oscillator, a monitor configured to monitor a first frequency of the first light, and a controller configured to control a second frequency of the second light, based on a difference between the first frequency and the second frequency so as to reduce the difference.

Abstract: In a network design apparatus, a full channel evaluator determines whether all wavelength channels for main signals can deliver the main signals of an existing optical network. When it is found that one or more wavelength channels cannot deliver main signals, a chromatic dispersion evaluator determines whether there are a specified number of wavelength channels that satisfy a specified chromatic dispersion condition. An optical signal-to-noise ratio (SNR) evaluator extracts a specified number of wavelength channels out of those satisfying the chromatic dispersion condition in descending order of optical SNRs thereof, and determines whether the extracted wavelength channels satisfy a specified optical SNR condition.

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 monitor for monitoring OSNR of data being carried via an optical network link, the monitor obtains an optical signal from the link, comprises a loop of a non-linear optical medium capable of producing a back reflected signal to the optical signal and of looping the back reflected signal; and comprises a device for extracting a portion of the looped back reflected signal from said loop. The monitor further comprises a first photodetector for measuring power of the optical signal and a second photodetector for measuring power of the extracted portion of the looped signal. Finally, there is a processing unit for determining OSNR of the optical signal based at least on readings of the first and the second photodetectors.

Abstract: The present invention relates to the quality monitoring of optical signals, which have different symbol rates and generated by different modulation schemes, used for example in a wavelength division multiplexing network. The apparatus according to the invention includes an optical splitter for outputting the input optical signal to a first optical route and a second optical route, an optical coupler for coupling a optical signal from the first optical route with a optical signal from the second optical route, a delay unit provided on the first optical route, and a phase shift unit provided on the first optical route or the second optical route.

Abstract: Described herein are systems and methods for a field-configurable optical network terminal (ONT) device at a subscriber to provide one or more communication services to the subscriber. The field-configurable ONT device is of a modular design operable for the insertion of additional communication modules or removal of existing communication modules from the ONT device for scaling the device to increased or decreased communication capacity as desired.

Abstract: A receiver for a communications link includes a receiver module and a host receiver. These two components can be tested independently. In one embodiment, the receiver module is characterized with respect to noise and distortion. The noise performance can be determined by comparing input and output signals of the receiver module, to determine the relative noise of the receiver module. The distortion performance can be determined by comparing the distortion of input and output signals of the receiver module, using a reference host receiver that includes an equalizer. The host receiver can be tested by using a reference receiver module.

Abstract: A method and apparatus for implementing optical network quality using bit error rate and chromatic dispersion. According to one embodiment of the invention, a method includes the provision of quality of service in a wavelength division multiplexing optical network that supports a plurality of bit rates. As part of this method, the cumulative noise and cumulative chromatic dispersion for each available path as a whole is determined, where an available path is a series of two or more nodes each connected by an optical link on which a set of wavelengths is available for establishing a lightpath. In addition, different grades of path quality are distinguished based on bit error rate (BER), where BER is based on cumulative noise and bit rate. Furthermore, a minimum path quality is required based on chromatic dispersion decibel penalty, where chromatic dispersion decibel penalty is based on cumulative chromatic dispersion and bit rate.

Abstract: There is provided a method for determining an in-band noise parameter, such as the Optical Signal-to-Noise Ratio (OSNR), on an optical signal-under-test (SUT) propagating along an optical communication link and comprising a data-carrying signal contribution of any arbitrary degree of polarization and a noise contribution. A spectral shape trace of signal contribution in the SUT is estimated using a reference optical spectrum trace of a reference signal which comprises a signal contribution that is spectrally representative of the signal contribution of the SUT and a noise contribution which is at least approximately known. The signal contribution is mathematically discriminated from said noise contribution in the SUT using the spectral shape trace and the test optical spectrum trace. The in-band noise parameter is then determined at least from the mathematically discriminated noise contribution.

Abstract: Techniques and devices for measuring phase noise in radio frequency (RF), microwave, or millimeter signals based on photonic delay.

Abstract: A receiver for a communications link includes a receiver module and a host receiver. These two components can be tested independently. In one embodiment, the receiver module is characterized with respect to noise and distortion. The noise performance can be determined by comparing input and output signals of the receiver module, to determine the relative noise of the receiver module. The distortion performance can be determined by comparing the distortion of input and output signals of the receiver module, using a reference host receiver that includes an equalizer. The host receiver can be tested by using a reference receiver module.

Abstract: A system assesses a column of gas in an atmosphere. The system includes an optical transmitter for transmitting (a) an online signal tuned to an online wavelength of gas, (b) an offline signal tuned to an offline wavelength of the gas, and (c) an optical signal for providing altimetry data. A modulator is included for modulating the online signal with a first stepped chirp waveform and modulating the offline signal with a second stepped chirp waveform. A processor assesses the column of gas, after receiving a returned online signal, a returned offline signal and a returned optical signal. A lock-in amplifier is included for (a) multiplying a returned signal with the first stepped chirp waveform to obtain a detected online signal, and (b) multiplying the returned signal with the second stepped chirp waveform to obtain a detected offline signal. The processor is configured to remove ground reflections from the optical signal to obtain scattered noise, and assess the column of gas based on the scattered noise.

Abstract: An example apparatus includes a mode selective detector, a measurement module, a difference calculator and a threshold and alarm module. The mode selective detector detects a plurality of modes of a spatially multiplexed signal. The measurement module measures a parameter for the plurality of modes of the spatially multiplexed signal, wherein the parameter is a power or a signal to noise ratio (SNR). The difference calculator compares the measured parameter among a subset modes and/or among a known set of unperturbed parameters and determines a differential, the subset including at least one mode. The threshold and alarm module sets an alarm indicator when the differential is out of bounds.

Abstract: An optical transceiver calibration system and manufacturing method to fabricate a dual closed loop control transceiver are provided. The calibration system and method includes measuring an operating temperature and determining operational parameters based upon the operating temperature. The operational parameters may include, for example, a target power for transmitting a digital one, a target power for transmitting a digital zero, a modulation current, and a bias current. A bias may be added to the temperature to account for the difference between the temperature at the temperature sensor and the optical equipment. The operational parameters are preferably calculated independently of each other and are used as initial values during operating modes and allow the control loop to converge more quickly. The optics data is may be scanned electronically via bar code or some other electronic format prior to test. The software residing on the module then calibrates and configures the transceiver.

Abstract: A method and a device for detecting Inband Optical Signal to Noise Ratio (OSNR) are provided in the present invention, wherein the method includes the following steps: obtaining a signal power PCW1 of a first optical signal at a transmitting end, a signal power PCW2 of a second optical signal at the transmitting end, and a total signal power PS; obtaining a ratio k1 of the PCW2 to the PS and a ratio k2 of the PCW1 to the PCW2 according to the PCW1, PCW2 and PS; obtaining a signal power P?CW1 of the first optical signal at a detection point and a signal power P?CW2 of the second optical signal at the detection point; obtaining a ratio K3 of the P?CW1 to the P?CW2 according to the P?CW1 and the P?CW2; and obtaining the Optical Signal to Noise Ratio according to the k1, k2, and k3.

Abstract: An apparatus comprising at least one processor configured to implement a method comprising receiving a path computation request comprising at least one path computation constraint, and determining whether there is a path through an optical network that satisfies the path computation constraints. Also disclosed is an apparatus configured to process a data structure comprising a flags field comprising at least one flag having one of an active state or an inactive state, wherein each flag is representative of an optical quality constraint.

Abstract: A method of monitoring optical parameters of a modulated optical signal comprises receiving a first optical power, Xi, of said optical signal for a first bandwidth, Bi, across the said optical signal and receiving a second optical power, Xj, of said optical signal for a second bandwidth, Bj, across the said optical signal. The method comprises obtaining a power spectral density description of said optical signal. The method comprises determining an optical signal to noise ratio of said optical signal. The optical signal to noise ratio depends on said first optical power, Xi, said second optical power, Xj, and said power spectral density description. The method also comprises generating a data signal indicative of said optical signal to noise ratio.

Abstract: Various embodiments relate to an in-band measurement of the optical signal-to-noise ratio (OSNR) of an optical signal in an optically-amplified transmission system. A demodulation device may tap a transmission fiber to receive an optical signal containing a low-frequency signal. A filter may implement first and second passbands to filter portions of an optical channel in the optical signal. Once the filtered channel is converted to first and second target electrical signals, a measurement circuit may take measurements of DC and AC components for each of the target electrical signals. Based on measurements of the two target electrical signals, the demodulation device may calculate the OSNR as a function of the DC and AC components, or as a function of the adjustment factors between first and second passbands of the optical channel represented by the first and second target electrical signals.

Abstract: A method and apparatus for establishing a terahertz link using a multi-element lens array that comprises a plurality of active beam steering device are disclosed. For example, the method receives detected terahertz signals from one or more detectors, where an active beam steering device is deployed with each of the one or more detectors, and determines, for each of the detected signals, if the detected signal is out of focus from a focus point. The method applies a corrective signal to each active beam steering device that corresponds to a detected terahertz signal that is out of focus from the focus point, wherein the corrective signal causes the detected signal to be redirected, and measures a signal-to-noise ratio of the detected signals. The method then establishes the terahertz link via at least one of the detected terahertz signals with a highest signal-to-noise ratio.

Abstract: An apparatus includes an oscillator circuit configured to generate a certain oscillation signal, an adder configured to add the oscillation signal to the tap coefficient of any of one or more taps of the transversal filter, a signal-quality measurer configured to measure a signal quality of a signal output from the transversal filter, and a tap-coefficient adjuster configured to control the value of the tap coefficient so that an optimal amount of shift in the signal quality of the output signal is achieved when the oscillation signal is added to the tap coefficient.

Abstract: A method comprises: acquiring, for a number nSOP of varied State-Of-Polarization analysis conditions of the input optical signal, nSOP polarization-analyzed optical spectrum traces, the distribution of the input optical signal of said SOP analysis conditions being approximately known; mathematically discriminating said signal contribution from said noise contribution within said optical signal bandwidth using said polarization-analyzed optical spectrum traces, said mathematically discriminating comprising: obtaining a differential polarization response that is related to the optical spectrum of said signal contribution by a constant of proportionality; estimating the constant of proportionality of a differential polarization response to the optical spectrum of said signal contribution as a function of said number nSOP; estimating the optical spectrum of said noise contribution from said input optical signal, within said optical signal bandwidth using said constant of proportionality and said differential pola

Abstract: A system including a device equipped with a reception section, a reception condition detection section and a control section. A partner device emits laser light and modulates the laser light in accordance with transfer subject information. Relative positions of the partner device and the device are adjusted to a communication-possible position, at which the laser light from the partner device is incident in a light reception region of the device. In this state, the reception section receives the transmission subject information from the partner device by detecting the incident laser light and demodulating the transmission subject information therefrom. The reception condition detection section detects a deterioration in a reception condition. If a deterioration in the reception condition is detected, the control section produces a warning or stops emissions of laser light from the partner device.

Abstract: Systems and methods are described that measure the OSNR of an optical channel. Embodiments provide OSNR measurement methods that distinguish the intensities of the coherent modulated signal from the incoherent noise intensity occupying the same optical band using a calibration factor ?.

Abstract: Systems and methods are described that measure the OSNR of an optical channel. Embodiments provide OSNR measurement methods that distinguish the intensities of the coherent modulated signal from the incoherent noise intensity occupying the same optical band using a calibration factor ?.

Abstract: For determining OSNRreal of a real optical signal carried in an optical network link, real the following has been proposed: tapping a portion of the real optical signal, altering the tapped signal portion by adding to it in-band artificial noise signal, thus obtaining a combined signal, scattering the combined signal by stimulated Brillouin or Raman scattering (SBS or SRS) in an optical element, extracting a signal back reflected by SBS/SRS from the optical element, determining OSNRcomb of the back reflected signal and deriving the OSNRreal from the OSNRcomb knowing absolute and/or relative power of the added artificial noise.

Abstract: A WDM optical transmission system includes a plurality of optical nodes optically coupled by a transmission line, a processor that is operative to calculate an amount of adjustment of a reception level capable of increasing an optical signal-to-noise ratio for each channel of the WDM light reaching the optical node positioned at a receiving end of the unit section based on information on amplification operation of the WDM light in at least one optical-amplification repeating node disposed on the optical transmission line in the unit section, and to adjust a power level corresponding to each channel of the WDM light transmitted on the transmission line from the optical node positioned at a transmission end of the unit section in accordance with a calculation result of the calculation.

Abstract: An optical node may include a plurality of optical input components operable to receive a plurality of signals communicated in an optical network and a plurality of optical output components operable to transmit a plurality of signals to be communicated in the optical network.

Abstract: An optical signal quality monitor includes a splitter splitting an input optical signal into two signals; a low-frequency converter converting one split optical signal to a low frequency signal by modulating the optical signal with a frequency offset signal; and an intensity ratio calculator calculating an intensity ratio between the low frequency signal and the other split optical signal, thereby appropriately confirming the quality of a high-bit rate optical signal. The monitor includes plural processing lines, each line including the splitter, the low-frequency converter, and the intensity ratio calculator. At least one line includes an optical noise superimposer superimposing optical noise on the one split signal before inputted to the converter or an optical band-pass filter transmitting the one split signal before inputted to the converter. The monitor includes a polarization state changer changing the polarization state of the input signal before inputted to the splitter.

Abstract: A method for monitoring wavelength-division multiplexed (WDM) signal for detecting signal drift of objective signals, including generation of one or more objective signals and a guard signal. The guard signal has a wavelength that is within a range defined by a guard channel. The first and second objective signals and the guard signal are wavelength-division multiplexed to generate a wavelength-division multiplexed signal. The first objective signal, the second objective signal, and the guard signal are assigned to a first multiplexed objective channel, a second multiplexed objective channel, and a multiplexed guard channel, respectively. The wavelength-division multiplexed signal is received by a monitor and then the error rate of the multiplexed guard channel is determined.

Abstract: An optical communication device comprises a variable dispersion compensator, a photoelectric converter, and a processor. The variable dispersion compensator compensates an amount of wavelength dispersion of an optical signal received from an optical transmission line. The photoelectric converter converts the compensated optical signal into an electrical signal. The processor is operative to extract a frequency of the converted electrical signal, and to discriminate bit information of the electrical signal based on the frequency extracted using a decision phase and a decision threshold. The processor is operative to detect bit error information that is information related to an error of the discriminated bit information, and to control the amount of wavelength dispersion based on the detected bit error information.

Abstract: In a passive optical network, a downstream transmission rate from an OLT to multiple ONTs can be optimized by matching a transmission scheme for frames addressed to a channel to the downstream transmission characteristics of the channel. An FEC coding can be made channel dependent so that channels with low error rates can use minimal protection, and therefore minimal overhead, while channels with high input bit error rates can use the level of FEC coding required to produce a desired output bit error rate.

Abstract: In a passive optical network, an upstream transmission rate from an ONT to an OLT can be optimized by matching a transmission scheme for a channel to the upstream transmission characteristics of the channel. An FEC coding can be made channel dependent so that channels with low error rates can use minimal protection, and therefore minimal overhead, while channels with high input bit error rates can use the level of FEC coding required to produce a desired output bit error rate.

Abstract: An OSNR measuring device n OSNR measuring device includes an input port to which a signal light is given; a wavelength filter which includes a variable passband, and selectively takes out an optical component corresponding to a signal optical wavelength to be measured from the signal light; a wavelength control circuit which controls the passband of the wavelength filter; a delay interferometer which branches a light output from the wavelength filter and delays one of the branched lights with respect to the other branched light and in which the branched lights are made to interfere with each other; a photodetector which detects a power of a delay interference light output; and an OSNR calculation circuit which calculates, based on a bandwidth of a passband of the wavelength filter and the power of the delay interference light, an optical signal to noise ratio of a signal optical wavelength to be measured.

Abstract: Optical regeneration is expensive to implement and maintain. A method or corresponding apparatus in an example embodiment of the present invention enables a user to plan an optical regeneration in a network with a reduction of optical regeneration compared to unplanned deployment. An optical regeneration planning tool according to an example embodiment of the present invention can graphically display a representation of a network topology with optical regeneration sites and enable the user to plan optical regenerations at a subset of the sites as a function of characteristics of models of optical network elements and paths within the network topology. Through use of the optical regeneration planning tool, a service provider can save on network deployment and future servicing of optical regeneration equipment.

Abstract: In accordance with various aspects of the disclosure, a method, an apparatus and a system for characterizing and compensating for deterministic phase nonlinearities and distortion inherent in radio frequency and optical components utilized to synthesize a single sideband suppressed carrier optical waveform in the presence of random phase noise generated by an optical carrier source is disclosed. The method comprises mixing a modulated optical signal with a continuous wave optical signal in an optical coupler; optically heterodyning the mixed signal output from the optical coupler in a detector to produce a radio frequency waveform; and analyzing the produced radio frequency waveform in a processor based on a phase history of a preselected continuous wave signal to measure distortion characteristics of the radio frequency modulated optical signal.

Abstract: An apparatus for measuring an OSNR for a communication channel in a WDM optical communications system includes a signal control unit, a receiving unit, and a measuring unit. The signal control unit controls spectral width reduction for an optical signal sent through a target channel. The receiving unit receives spectral data measured from the optical signal received by the target channel under control of the control unit. The measuring unit, based on the spectral data received by the receiving unit, measures the OSNR of the target channel.

Abstract: A method and apparatus for establishing a terahertz link using a multi-element lens array that comprises a liquid lens are disclosed. For example, the method receives detected terahertz signals from one or more detectors, where a liquid lens is deployed with each of the one or more detectors. The method determines, for each of the detected signals, if the detected signal is out of focus, and applies a corrective voltage to each liquid lens that corresponds to a detected terahertz signal that is out of focus, wherein the corrective voltage adjusts a focus of the detected signal. The method measures a signal-to-noise ratio of the detected signals, and establishing a terahertz link via at least one of the detected terahertz signals with a highest signal-to-noise ratio.

Abstract: The present invention provides methods and systems for efficiently computing optimal optical launch powers for meshed optical networks. The present invention can be utilized to find optimal launch powers for multiple wavelengths in a meshed dense-wave division multiplexed (DWDM) system. Generally, the present invention ensures Q exceeds a threshold for OSNR, and then the launch powers are optimized based on nonlinear penalties. If Q is below the threshold, DWDM equipment changes/additions are incorporated to provide adequate OSNR. The present invention provides a computationally efficient mechanism to optimize launch powers in 10 Gb/s, 40 Gb/s, 100 Gb/s, etc. highly-meshed optical networks.

Abstract: The subject matter disclosed herein relates to determining a photosensor operating point.

Abstract: The optical signal sampling apparatus and the optical signal monitor apparatus are configured of an optical combiner for combining an optical signal to be sampled and a sampling light pulse with each other and an electroabsorption modulator. The electroabsorption modulator has two optical terminals for inputting/outputting the light and a power supply terminal for applying the electric field to the optical path connecting the two optical terminals, and has such a characteristic that the absorption rate of the light propagating through the optical path changes in accordance with the magnitude of the electric field, the light emitted from the optical combiner is received by one of the two optical terminals, and the absorption rate is increased when the sampling light pulse is not incident while the absorption rate is decreased when the sampling light pulse is incident.

Abstract: According to the invention, various noise currents are added to the electrical data signal after the opto-electric conversion of an optical data signal, and an optimum decision threshold for the electrical data signal equipped with this noise current is determined for each noise current. Values for a median signal current and for a median noise current of the amplified spontaneous emission are subsequently determined from the value pairs of the optimum decision threshold and the added noise current in accordance with a computation rule that is based on a noise model, and the optimum signal-to-noise ratio is calculated from their quotient. The method may also be advantageously implemented by means of simple expansions of common receiver devices.

Abstract: Some optical communications networks include one ingress fiber, an n-way signal coupler, and n egress fibers, where each fiber may carry signals in one or both directions. A method and apparatus for testing and monitoring data communications immediately before and after the coupler is provided. Benefits include improved ability to identify and locate system faults, and improved ability to monitor data quality and content.

Abstract: A transmitter for a communications link is tested by using a (software) simulation of a reference channel and/or a reference receiver to test the transmitter. In one embodiment for optical fiber communications links, a data test pattern is applied to the transmitter under test and the resulting optical output is captured, for example by a sampling oscilloscope. The captured waveform is subsequently processed by the software simulation, in order to simulate propagation of the optical signal through the reference channel and/or reference receiver. A performance metric for the transmitter is calculated based on the processed waveform.

Abstract: A scrambling initial value is shared without deteriorating transmission efficiency. On the transmission side, a scrambling initial value is created based on a part of a physical layer header not scrambled, a transmission signal sequence scrambled is created by calculating an exclusive-OR operation between a scrambled sequence generated from the scrambling initial value and a transmission data sequence, and is transmitted. On the reception side, the same descrambling initial value as the scrambling initial value is created based on a part of a physical header of a reception frame, and a reception data sequence is descrambled by calculating an exclusive-OR operation between a descrambled sequence generated from this descrambling initial value and a reception signal sequence scrambled.

Abstract: A system for measuring properties of a medium includes an electromagnetic generator for forming a CW carrier, a digital encoder for forming a digital message, and a modulator for modulating the CW carrier with the digital message to form a digitally modulated CW carrier. The medium provides a channel for propagating the digitally modulated CW carrier. The system further includes a receiver configured to receive the propagated, digitally modulated CW carrier, and a processor for measuring at least one property of the medium. The medium may be disposed within a gaseous atmosphere, a body of water, or a cell of a laboratory.

Abstract: An attenuation amount corresponding to each wavelength at OADM node is optimized according to a calculation result in a network management system (NMS), so that an optical signal level diagram according to traffic volume variations is set, the level diagram allows each of optical signal quality indexes at terminal nodes for all wavelengths to be maintained at a required threshold value or more, and allows an optical signal quality index of a specific wavelength to be improved. Then, an FEC circuit in an optical receiver corresponding to the specific wavelength is turned OFF or the error correction ability is lowered, whereby power consumption of an overall optical network is efficiently reduced.

Abstract: method and apparatus for optimizing a decision threshold of an optical receiver is used to solve a problem of affecting system stability and reliability. The method comprises: determining a maximum value and a minimum value of an adjustment range of the decision threshold, and determining an adjustment step of the decision threshold (10); adjusting a decision threshold value within the adjustment range of the decision threshold, and separately detecting pre-FEC BERs corresponding to different decision threshold values (11); and searching for a minimum value in the detected pre-FEC BERs, a decision threshold value corresponding to the minimum value being an optimal decision threshold value (12). The apparatus comprises a decision threshold adjusting unit, a pre-FEC BER detecting unit, a decision threshold control unit and an optimal decision threshold determining unit.

Abstract: Techniques, apparatus and systems to provide adjustable bit rate optical transmission using programmable signal modulation in optical communication systems.