Abstract: A robust and redundant status link is established by a first multi-channel optoelectronic device with a second multi-channel optoelectronic device in a multi-channel communication link. Transmitter bias currents are effectively modulated with a status link modulation signal representative of status data and subsequently modulated with primary data modulation signals. The resulting signals are transformed into optical signals and transmitted over the link as main communication links combined with a status link. At the second device, the optical signals are received and converted to electrical signals. The receipt of the optical signals creates multiple receiver bias currents, which may be monitored to detect the status link modulation signal. The second device may adjust various operating parameters in response to the information conveyed by the status link.

Abstract: A drive circuit and method of controlling a quantum well modulator are disclosed. The drive circuit can be disposed in an optical transceiver having a quantum well modulator configured to retro-modulate an incoming optical signal. The drive circuit can include separate modulating and bias voltage sources. A level of the modulating voltage and the bias voltage can be determined based on an ambient temperature of the optical transceiver and can be adjusted to compensate for variations in the optical performance of the quantum well modulator. The quantum well modulator can be controlled in intervals. The modulating voltage can be applied to the quantum well modulator during a first interval. A current associated with the modulating voltage can be returned to the modulation voltage source during a second interval. A timing of the first and second intervals can be based on electrical properties of the quantum well modulator.

Abstract: A method of testing a dual-polarization optical transmitter comprising a pair of polarization transmitters for respectively generating first and second polarization signals, and a polarization combiner for generating an optical signal composed of the first and second polarization signals with respective orthogonal polarization vectors. Each of the polarization transmitters is controlled to transmit respective polarization optical signals having predetermined characteristics. An output of the dual-polarization optical transmitter is tapped to obtain a first tap signal representative of the first polarization signal, and a second tap signal representative of the second polarization signal. A relative angle between respective polarization vectors of the tap signals is controlled, and the first and second tap signals combined to generate a combined light. A power level of the combined light is detected, and processed to obtain information about the performance of the dual polarization transmitter.

Abstract: Safety and power control arrangement and method for optical communication apparatus, where a first circuit pack emitting an optical signal (OS1) and at least a second and a third circuit pack (2, 3) are connected in series via optical fibers (4, 5). A power monitor (26) connected to an output (27) of the at least second circuit pack (2) reduces the signal power (PW2) output from the second circuit pack (2) to a pre-determined safe value if a loss-of signal monitor (34) of a next circuit pack (3) forwards a loss-of-signal control signal (LOC3). The advantage is that the maximum allowable value is achieved at the input of an interrupted fiber section and the non-interrupted circuits can still receive the optical signals with a reasonable power level.

Abstract: A method and apparatus for measuring the optical power of very weak light arriving at a receiver, by using a photon detector, are provided. A photon detector detects the presence or absence of the arrival of a photon in accordance with bias application timing. For a train of optical pulses coming in at an arbitrary timing in respective time slots, the bias application timing is sequentially shifted within the range of a time slot. Each time a shift is made, the number of photons detected is counted by a photon counter. Based on this number of photons, the optical power of the train of the optical pulses is measured.

Abstract: A control device (13) for scheduling the transmission of signals from a plurality of transmitters (14, 15, 16, 17, 18, 19, 20, 21). The control device (13) comprises an evaluation element (22) arranged to determine the power level of the signals received from each of the transmitters and a scheduling element (23) adapted to determine a transmit schedule comprising the order that the plurality of transmitters should transmit based on the power levels of the signals received from the transmitters (14, 15, 16, 17, 18, 19, 20, 21). A method of operation and a node incorporating the control device is also disclosed.

Abstract: A wavelength division multiplexer terminal with a multiplexer arrangement with a first switching matrix, and a demultiplexer arrangement with a second switching matrix allows flexibility for connection transceivers to ports of the wavelength division multiplexer and wavelength division demultiplexer respectively. Optical monitoring receivers are connected upstream the wavelength division multiplexer and downstream the wavelength division demultiplexer for managing and supervising connections.

Abstract: An optical receiving apparatus includes a variable dispersion compensation unit, a delay interference unit, a photoelectric converter, a polarization control unit for control the polarization state of an optical signal inputted to the photoelectric converter, a received data processing unit for monitoring the number of error occurrences, and a control unit for controlling the dispersion compensation amount at the variable dispersion compensation unit and the optical phase control amount at the delay interference unit, based on information on the number of error occurrences from the received data processing unit.

Abstract: A method and apparatus suitable for controlling the power of a channel in an optical network are described. A control system for a variable optical attenuator includes a processing element arranged to: (a) receive a signal indicative of the radiation power of an optical signal output from a variable optical attenuator; (b) determine an error signal in dependence upon the received signal and a predetermined target radiation power level; (c) determine a control signal for controlling the attenuation of the variable optical attenuator in dependence upon the error signal and a gain factor; and (d) repeat the operations of (a) to (c). The control system is arranged to utilize a first value of the gain factor during a first time period and a second, lower value of the gain factor during a second time period. Such a control system can be used to control the introduction of a channel in a node of an automatically switched optical network.

Abstract: A phase modulated signal receiver includes an operation part and a control part. An input power of a received light signal is measured based on current monitored by a monitor circuit. The operation part is configured to correct, on the basis of a ratio of the input power measured when a delay of a phase reference light output from a delay interferometer is a first delay and the input power when the delay of the phase reference light is a second delay, a value of the current monitored by the monitor circuit when the delay is the first delay to a corrected value that depends on the input power of the received light signal obtained when the delay is the first delay. The control part is configured to control the delay of the phase reference light of the delay interferometer by comparing the current monitored when the delay is the first delay and the corrected value of the current monitored when the delay is the second delay and maximizing or minimizing the current monitored by the monitor circuit.

Abstract: A wavelength division multiplexing transmission system, the system comprising: a plurality of channels at different wavelengths, each channel comprising a transmitter, a receiver, and one or more amplifiers, the system further comprising an encoder for encoding data with a coding, and; a decoder for decoding transmitted data; prioritizing means for prioritizing the data on each channel; monitoring means for monitoring directly or indirectly, raw (uncorrected) bit errors on each channel; power adjusting means for, varying the power on a channel in response to the bit error rate.

Abstract: The present invention discloses a method and a device for optimally adjusting the decision level of a receiver, wherein the method includes: monitoring optical power received by an optical receiver; determining whether the variation amplitude of the optical power is greater than a predefined value; if yes, then updating a current initial value of the decision level according to the optical power; obtaining an error signal of a transmitted signal from the output end of the optical receiver; determining whether the decision level needs adjusting according to the error signal; if yes, then further analyzing the error signal according to the current initial value to obtain the result of the analysis; otherwise, exiting the execution program directly; and adjusting the decision level from the current initial value according to the result of the analysis.

Abstract: An optical transmission module includes a variable wavelength light source; an alternating current adding unit that adds an alternating current to a drive current to the variable wavelength light source; a first detector to detect optical power of an output light; a filter to input the output light from the variable wavelength light source in which transmission wavelength periodically increases and decreases; a second detector to detect optical power of transmitted light transmitted through the filter; an extraction unit to extract a wavelength fluctuation component of the output light based on the optical power of the output light and the optical power of the transmitted light; a phase comparison unit to compare a phase of the wavelength fluctuation component with a phase of the alternating current; and a wavelength controller to control a wavelength of the output light by controlling a temperature of the variable wavelength light source.

Abstract: A method and apparatus for controlling the power level of an optical signal includes detecting the loss of a supervisory signal counter-propagating in an optical fiber.

Abstract: An optical transmitter disabling device for controlling an optical transmitter, particularly of an optical network termination node of a passive optical network comprising a monitoring module and a disabling module, the monitoring module being adapted to determine at least when the optical transmitter is active, the disabling module being adapted to be connected to an activation input of the optical transmitter and wherein the disabling module is adapted to interrupt an activation signal to the optical transmitter at least when the monitoring module determines that the optical transmitter is active outside of a predetermined time interval.

Abstract: A first signal shaper generates a first signal having a first asymmetry. A second signal shaper generates a second signal having a second asymmetry different from the first asymmetry. The first and second signals have approximately the same peak-to-peak amplitude. An AC measurement element acquires a first scaled representation of the shape of the first signal and a second scaled representation of the shape of the second signal. A DC measurement element receives the first signal and the second signal and generates a first value responsive to the first signal and a second value responsive to the second signal. A processor calculates a first factor responsive to the shape of the first signal and a second factor responsive to the shape of the second signal. The processor applies the first and second factors and the first and second values in a function that generates the AC/DC cross-calibration coefficient.

Abstract: An evaluation method of an optical receiver of an optical communication system, including a DPSK (Differential Phase Shift Keying) signal modulated by a specific data series, a delay interferometer for performing delay detection on the DPSK signal, an optical receiver for receiving each of two optical outputs of the delay interferometer and outputting a difference signal, and a spectrum analyzer for measuring a spectrum of an output electrical signal of the optical receiver, comprising monitoring a specific frequency component of the spectrum analyzer and detecting a delay difference and a deviation in optical reception level between the two outputs of the delay interferometer and the optical receiver.

Abstract: The present invention provides a method for determining the bandwidths of optical fibers, wherein the method provides the coupling of light with a first optical power and a first modulation frequency into an optical fiber, as well as measuring a first signal level as a function of the optical power of the light of the first modulation frequency, coupling light with the second optical power and a second modulation frequency into the optical fiber, measuring a second signal level as a function of the optical power of the light of the second modulation frequency, and determining the bandwidths of the optical fibers as a function of the first and second coupled optical [power and/or] the measured first and second signal levels while using a predetermined specification that describes the frequency-dependent attenuation response of the optical fiber, wherein the first and the second modulation frequencies have essentially the same value.

Abstract: The invention relates to a switchable infrared filter, consisting of a diamond carrier material (1), whereon a filter material (6), which is made of a thermochromic material, is disposed on one side and which can be connected to a heating device (2, 3).

Abstract: The present invention allows immediate reading of a monitor voltage of a required arbitrary burst cell and provides a burst light receiving power monitor circuit that monitors the monitor voltage of a burst cell, the burst light receiving power monitor circuit comprising: a memory that includes a plurality of areas and that prepares an address for each area; a monitor voltage forming section that converts input signal light of the burst cell to a digital monitor voltage amplitude; and a controller that continuously stores the monitor voltage amplitude from the monitor voltage forming section in each area of the memory specified with an address by a control signal externally inputted according to the timing of the burst cell and that controls reading out a monitor voltage from an arbitrary area of the memory specified with an address by an external memory access signal.

Abstract: A method is provided for protection switching in an optical network. The method may include establishing a baseline power level for a channel. The method may further include receiving a signal associated with the channel via each of a first path of the optical network and a second path of the optical network. The method may also include monitoring a power intensity of the signal received via the first path. The method may additionally include protection switching from the signal received via the first path to the signal received via the second path in response to a determination that the baseline power level exceeds the power intensity of the signal received via the first path by a predetermined threshold.

Abstract: A method is provided for protection switching in an optical network.

Abstract: A photodiode array includes a plurality of monitoring photodiodes capable operating in a voltage mode configuration each able to provide a voltage indicating an intensity of an incident light. Integrated with the monitoring photodiodes is a reference diode configured to produce reference voltages in response to reference currents supplied to that diode. The monitoring photodiodes and the reference diode may be integrated and have the same current-voltage characteristics and the same temperature, for example by fabricating them on the same substrate. The reference diode is supplied with the reference currents in dark manner, meaning without incident light impinging on the reference diode. The resulting reference voltages, the reference source currents, and the measured photo-voltage from the monitoring photodiodes are than used to determine an optical power value at any temperature within the operation temperature range.

Abstract: A device may include a communication interface to communicate with an optical line terminal and a processor. The processor may set an optical path from the optical line terminal to an optical network terminal, the optical path including one or more optical network elements. In addition, the processor may obtain, from the optical line terminal, a status reading of the optical network terminal when the optical path is set. Further, the processor may obtain, from the optical line terminal, a power reading at the optical network terminal when the optical path is set. The processor may record the status reading and the power reading.

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 method and apparatus for use in an optical receiver are provided for monitoring the received optical power in the optical receiver over wide range of optical power levels with high accuracy. An adjustable resistor circuit of the apparatus has a first resistor and one or more second resistors that may be switched into and out of parallel with the first resistor to vary the resistance of the adjustable resistor circuit. A controller of the optical receiver controls the switching of the one or more second resistors into and out of parallel with the first resistor. Varying the resistance of the adjustable resistor circuit in this manner causes the value of the analog voltage signal representing the received optical power to be varied prior to being input to the ADC of the controller. In this way, the amplitude of the analog voltage signal is reduced when it is at the high end of the received power range so as not to exceed the input range of the ADC of the controller IC.

Abstract: An optical line terminal (OLT) performs power management control in a passive optical network (PON) by acquiring a respective reception level for each optical network unit (ONU) in the PON and maintaining a reception table that stores the respective reception level for each ONU. Prior to receiving a burst signal from an ONU, it sets a reception threshold of an optical receiver at the OLT with the reception level of the ONU.

Abstract: A communication network is provided for interconnecting a network of digital systems, such as multimedia devices. Each node of the communication network may include a receiver and a transmitter. The receiver and transmitter of each node can be an optical receiver and transmitter. The optical receiver is preferably powered by two power supply pins, each providing different supply amounts. An activity detector within the receiver can be powered from a first supply amount, and the signal path of the optical receiver can be supplied from a second supply amount greater than the first supply amount. The first supply amount is provided at all times, and the second supply amount is only provided if activity is detected. A voltage regulator which provides the first supply amount can be beneficially embodied on the same integrated circuit as a network interface to reduce the manufacturing cost of the network.

Abstract: A WDM fiber optic communication system is operative to transmit WDM signals between multiple nodes. Each node has a booster EDFA, and in-band and out-of-band supervisory channels monitoring the integrity of a link by generating and detecting respective in-band and out-of-band control signals. The booster EDFA receives the multiplexed WDM and IB signals and generates an output signal carried by fibers between the nodes. The booster EDFA switches from an automatic gain control regime upon detecting of at least one of the IB and OB control signals to an automatic power control regime upon loss of both IB and OB control signals. The output signal of the EDFA in the AGC regime has a high power sufficient for transmitting the WDM and IB signals, and has a low power in the APC regime sufficient for transmitting only the IB control signal.

Abstract: The present invention provides an optical receiver able to monitor the level of the optical input signal in accurate even when the level is quite small. The optical receiver comprises a photodiode to generate a photocurrent Ipd, a current mirror circuit to reflect the photocurrent into a mirrored current Imon, a current-to-voltage converter to convert the mirrored current Imon to a voltage signal, switch to connect/cut the current mirror circuit with the current-to-voltage converter, and a correction unit for subtracting a signal when the switch is connected from a signal when the switch is cut.

Abstract: An apparatus provides measurement of power of an optical signal transmitted in a wavelength multiplexing scheme, based on the optical spectrum and the information on the optical signal. A method provides measuring the power of an optical signal transmitted in a wavelength multiplexing scheme based on the optical spectrum of the optical signal and information acquired on the optical signal.

Abstract: A channel power estimator for estimating the power of each channel in a wavelength division multiplexed (WDM) signal, comprising filter means to select and output a sub-band of an incoming WDM signal, function application means to apply a weighting function at least once to the output from the filter means and then output the weighted signal to reconstruction means, storage means for storing optical characteristic data on at least the function application means, wherein the reconstruction means calculates an estimation of the power distribution of the incoming WDM signal using the weighted signal and the optical characteristic data.

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: An optical network unit useful in a passive optical network has capability for automatic shutdown upon detection of a malfunction, thereby protecting the integrity of upstream data transmitted in the network. The unit detects the generation of upstream light during intervals in which transmission is not authorized. In response, the light source of the unit is deactivated to prevent collisions with upstream data from other optical network units in the network.

Abstract: An optical network system having a global controller capable of controlling all the elements of the network. The controller receives performance data from each optical network element and calculates a performance value for each channel transmitting through the system. The controller then isolates the channel with the minimum performance value and tests possible changes in network element parameters to find a change which would increase this performance value. Once such a change is found, it is implemented and the system is reoptimized.

Abstract: Methods and apparatus for determining transmission power of a plurality of optical channels for transmission of the channels along respective paths obtained through an optical transmission system. Information is obtained indicative of the path of each channel through the optical transmission system, and each channel allocated to a group of channels in dependence upon the obtained information. A quality metric is determined for each group of channel, and a total transmission power for each group determined in dependence upon the determined quality metric.

Abstract: Techniques for measuring optical modulation amplitude (OMA) are disclosed. For example, a technique for measuring an OMA value associated with an input signal includes the following steps/operations. The input signal is applied to a photodetector, wherein the photodetector is calibrated to have a given responsivity value R, and further wherein the photodetector generates an output signal in response to the input signal. The output signal from the photodetector is applied to a radio frequency (RF) power meter, wherein the RF power meter measures the root mean squared (RMS) power value of the output signal received from the photodetector. The OMA value associated with the input signal is determined in response to the root mean squared (RMS) power value measured by the RF power meter. The OMA value may be determined as a function of a factor F derived from a relationship between an amplitude of a data signal and the RMS value of the data signal.

Abstract: A system and method for loading unutilized channels of a WDM system with noise to improve system performance. A transmitter amplifier may impart noise to unutilized channels by reducing amplifier input or providing feedback of the amplifier output. Noise signals may also be looped back to the transmitter from received signals.

Abstract: Provided are an apparatus and method for tracking a wavelength in a passive optical subscriber network in which a central base station and at least one subscriber terminal are connected via a remote node. The apparatus includes a first wavelength aligning unit multiplexing and aligning wavelengths of optical signals from a plurality of single-mode optical sources of the central base station; a second wavelength aligning unit multiplexing and aligning wavelengths of optical signals transmitted to the remote node from a plurality of single-mode optical sources of the subscriber terminal; and a third wavelength aligning unit demultiplexing and aligning wavelengths of optical signals from the second wavelength aligning unit, the third wavelength aligning unit being included in the central base station.

Abstract: Methods and apparatuses are provided for performing jitter measurements in a transceiver module. Accordingly, there is no need to use expensive test equipment that must be inserted into and removed from the network in order to obtain these measurements. In addition, because the measurements can be obtained at any time without any interruption in communications over the network, jitter performance can be monitored more closely and more frequently to facilitate better and earlier diagnosis of problems that can lead to failures in the network.

Abstract: An optical signal quality monitor device includes a local oscillator that generates a local oscillation signal, with which a mixer mixes an input optical signal to output a mixed signal, of which at least one beat component a filter that extracts. An intensity detector detects intensity of the extracted beat component. The monitor device may thus accurately and rapidly monitor the quality of an input optical signal transmitted even at a higher bit rate.

Abstract: Provided is a multi-value optical transmitter in which a DC bias may be controlled to be stabilized so as to obtain stable optical transmission signal quality in multi-value modulation using a dual-electrode MZ modulator. The multi-value optical transmitter includes: D/A converters for performing D/A conversion on first and second modulation data which are set based on an input data series, so as to generate a first and a second multi-value signal, respectively; a dual-electrode MZ modulator including phase modulators for modulating light from a light source based on the first multi-value signal and the second multi-value signal, so as to combine optical signals from the phase modulators to output the optical multi-value signal; an optical output power monitor for detecting average power of the optical multi-value signal; and a DC bias control unit for controlling a DC bias for the dual-electrode MZ modulator, so as to maximize the average power.

Abstract: The present invention provides methods and systems to stabilize an optical network against nodal gain changes through two nested control loops for controlling node gain and node output power. The present invention includes two nested control-loops running at different update speeds including: an inner, faster, control-loop which sets the gains and losses within a node to achieve a node-gain target, and a node-gain target for the inner loop is set by an outer, slower, control loop that whose target is the node output power. Advantageously, the present invention reduces the problem of concatenated overshoot by minimizing the control-loop response to events that occur at other nodes.

Abstract: Differently designed measuring systems exist of which most contain a central signal processing unit and a number of electrical measuring components, and in which the measured values furnished by the measuring components are optically transmitted over optical wave guides. The aim of the invention is to provide a measuring system of this type, which has low power consumption and enables a reliable optical data transmission. To this end, an optical loop is provided between a central measuring unit (MG) and a sensor head (SK). Microprocessors (MP1, MP2), which are situated inside the central measuring unit (MG) and inside the sensor head (SK), carry out transmitting, measuring and monitoring tasks as a distributed controller with bi-directional data communication. A frame synchronization signal serves both for supplying power as well as for deriving a clock signal for block-oriented data transmission.

Abstract: Optical performance measurements are taken in an optical network and displayed in a form that allows an operator to enter fault information related to the measurements, or to automatically generate fault alarms to the operator, based on processing of the measurements. The optical measurements may be individual power measurements taken for each light-path at various points in each node it traverses, such as amplifiers, multiplexers/demultiplexers or at an interface with another node.

Abstract: A dispersion compensating apparatus includes a tunable dispersion compensator that dispersion-compensates an optical signal using a group delay property that is asymmetrical in bands outside an effective band; a set device that sets a dispersion compensation amount in the tunable dispersion compensator; and a shifter that shifts a central frequency of the effective band of the tunable dispersion compensator, based on the dispersion compensation amount set by the set device.

Abstract: Apparatus and methods for noise-feedback controlled optical systems are disclosed. In one aspect, an apparatus includes a receiver adapted to receive an optical signal and to convert the optical signal to a corresponding electrical signal, and a control circuit coupled to the receiver. The control circuit includes a monitoring component adapted to monitor a noise level of at least a portion of the electrical signal and to adjust a gain of the receiver based on the noise level. In an alternate aspect, an optical system includes a transmitter, a receiver, and a monitoring component adapted to monitor a noise level of at least a portion of the electrical signal and to adjust at least one of an amplification of the transmitter and a gain of the receiver based on the noise level.

Abstract: A system and method for an Avalanche photo-diode (“APD”) optical receiver and laser system to adjust its performance during system operation without disturbing network traffic. Very small changes may be adaptively applied to some key portions of the system by controlling a set of main system parameters including Q-factor; Bit Error Rate (BER); histograms of “1” and “0” levels; input optical power; and laser output power. This adaptive routine may be performed during operation of the system to keep the main system parameters close to their optimum value. During adjustment, the system may be divided into separate portions. The adjustment of each portion may be independent of the other portions of the system. For the optical network system, optimization and priority of different portions may be assigned based on network channel architecture.

Abstract: An output stage for WDM information transmission transmits a plurality of carrier waves modulated by an information signal and a filling lightwave. A first control circuit controls a desired power signal which determines the power of the filling light source so that the total power of carrier and filling lightwaves detected by a photodetector is held constant at a predetermined reference level. The filling light source is part of an assembly which is replaceably mounted at a first mounting location of the output stage. At a second mounting location of the output stage a second assembly comprising a second filling light source is mounted or adapted to be mounted. An auxiliary circuit is adapted to provide one of the two filling light sources with a continuously decreasing second desired power signal.

Abstract: In one embodiment, a control method, according to which a cascade of control messages is propagated between nodes of an optically transparent network, with each message being sent from a node to an adjacent downstream node to inform the latter about a control operation scheduled to be performed at the message-sending node and/or an upstream node that impacts an optical communication signal received at that downstream node. The cascade of control messages effectively creates an ad hoc control domain, in which control operations performed at various nodes of that domain can be coordinated to reduce unfavorable interactions between those control operations. By repeatedly propagating appropriate cascades of control messages through the network, control domains can be changed dynamically and adaptively to reflect any changes to the network topology, equipment, and/or traffic distribution.