Abstract: Disclosed herein is a method of encoding and/or decoding data for optical data transmission along a transmission link, as well as corresponding transmitters and receivers. The data is encoded based on an adaptive constellation diagram in a 2-D plane, said constellation diagram including a first and a second pair of symbols, wherein the symbols of the first pair of symbols are located at opposite sides of the origin of the 2-D plane at a first distance di from each other, and wherein the symbols of the second pair of symbols are located at opposite sides of the origin of the 2-D plane at a second distance d2 from each other. The method comprises a step of adapting the constellation diagram by varying the ratio of the first and second distances d1, d2 such as to minimize or nearly minimize a bit error rate in the transmitted data.

Abstract: This application discloses a communications network and a related device. In one embodiment, the communications network includes a first optical line terminal and a second optical line terminal. The first optical line terminal is configured to send, through a first passive optical network (PON) interface based on a first PON protocol, a first optical signal to the at least one second optical line terminal. The second optical line terminal is configured to process the first optical signal and send through a second PON interface based on a second PON protocol, a processed first optical signal to at least one customer-premises equipment during downstream data transmissions, and process a second optical signal and send, through the first PON interface based on the first PON protocol, the processed second optical signal to the first optical line terminal during upstream data transmissions.

Abstract: A repeater includes a pump light supplier configured to generate pump light; a first multiplexer configured to multiplex the pump light and a first wavelength division multiplexed optical signal; a second multiplexer configured to multiplex the pump light and a second wavelength division multiplexed optical signal; a first amplifier configured to amplify the first wavelength division multiplexed optical signal by use of the pump light; a second amplifier configured to amplify the second wavelength division multiplexed optical signal by use of the pump light; and a controller configured to control power of the pump light output to the first multiplexer and the second multiplexer, based on wavelength information about at least one of the first wavelength division multiplexed optical signal and the second wavelength division multiplexed optical signal.

Abstract: A system includes a waveform generator configured to generate a pulsed laser beam at a first wavelength. The system also includes at least one splitter configured to split the laser beam into multiple beams at the first wavelength. The system also includes at least one wavelength shifter configured to shift at least one of the multiple beams to another wavelength. The system also includes at least one combiner configured to combine the multiple beams into a multi-wavelength beam in which multiple wavelengths are co-aligned and propagating parallel to each other. The system also includes at least one nonlinear crystal configured to receive the multi-wavelength beam and generate multiple co-propagating beams using nonlinear wavelength conversion.

Abstract: A method (10) of changing operating mode of an optical amplifier in an amplifier chain in an optical network, the optical amplifier initially configured to operate in a first mode to apply a substantially constant first gain to an optical signal comprising a plurality of optical channels, the method comprising, after a time period unique to the optical amplifier within the amplifier chain (12), configuring the optical amplifier to operate in a second mode to apply a second gain to the optical signal so that the optical power of the optical signal is maintained at a target optical power dependent on a current plurality of optical channels in the optical signal (14).

Abstract: A level control circuit that generates output signal for level control includes: a control information storage that stores control information corresponding to a signal level, a control information circuit that outputs the output signal for level control corresponding to the signal level of a first input signal based on the control information stored in the control information storage; and an information update circuit that updates the control information of the control information storage according to the signal level of a second input signal.

Abstract: An optical receiving apparatus includes an optical amplification medium that receives an excitation light and an input light, an optical loss medium that receives an output light from the optical amplification medium, a monitor that detects a power level of an output light from the optical loss medium, a controller that controls a power of the excitation light such that the power level of the output light detected by the monitor is at a target value, and a receiver that receives the output light from the optical loss medium, the output light not being optically amplified.

Abstract: An optical amplifier includes: a first amplifier amplifying a signal light by a first excitation light; a variable optical attenuator attenuating the signal light; a second amplifier amplifying the signal light by a second excitation light; a mode selector selecting one of first and second modes; a gain controller, in first mode, controlling first and second excitation lights so that a gain of power of the signal light becomes constant; a first output controller, in second mode, controlling the first excitation light; a second output controller that, in second mode, controlling the second excitation light so that a spontaneous emission light having fixed level is outputted; and an attenuation controller controlling an attenuation of the variable optical attenuator according to an input level of the signal light in first mode, and controlling the attenuation to become a given value larger than a value of first mode in second mode.

Abstract: An optical output level control apparatus includes a detector configured to detect power of an input optical signal; an amplifier configured to amplify the input optical signal; a memory configured to store data that define a first curved line representing a relationship between the input power and a drive voltage of the amplifier for obtaining a first output level and data that defines a second curved line representing a relationship between the input power and the drive voltage of the amplifier for obtaining a second output level; a generator configured to correct at least one of the first and second curved lines and generate a target curved line representing a relationship between input power and a drive voltage of the amplifier for obtaining a target output level through interpolation based on the first and second curved lines at least one of which is corrected.

Abstract: A light power control system is used in a network in which a control signal is transmitted to instruct setting of a wavelength path. The light power control system is provided with a light amplifier control section configured to carry out a constant output control to a light amplifier which amplifies a light signal transmitted from a node to another node, when said node in said network receives the control signal; and a variable optical attenuator control section configured to adjust an attenuation quantity of a variable optical attenuator to attenuate a light power of the light signal on any of wavelength paths, when said node receives the control signal and moreover the light signal is transmitted on said any of wavelength paths of said node. It becomes possible to receive the data right in a receiving end by a simple unit when there is a change of the number of wavelength paths.

Abstract: A multi-wavelength light amplifier includes a first-stage light amplifier which has a first light amplifying optical fiber amplifying a light input, a second stage light amplifier which has a second light amplifying optical fiber amplifying a first light output from the first-stage light amplifier, and an optical system which maintains a second light output of the second-stage light amplifier at a constant power level. The first-stage and second-stage light amplifiers have different gain vs wavelength characteristics so that the multi-wavelength light amplifier has no wavelength-dependence of a gain thereof.

Abstract: An optical amplifier includes a semiconductor optical amplifier, a power monitor configured to monitor an optical power of out-of-signal-band noise output from the semiconductor optical amplifier, and a corrector configured to correct a relationship between a driving current for the semiconductor optical amplifier and a noise optical power based on the out-of-signal-band noise optical power monitored by the first power monitor.

Abstract: This specification describes technologies relating to controlling optical amplifiers. In one implementation, an optical amplifier is provided. The optical amplifier includes a light amplifying medium for receiving an input optical signal and outputting an output amplified signal; a first measuring block for measuring a change in power of the input signal; a pump laser for supplying pump light to the light amplifying medium; and an electronic control for controlling the power of the pump light in response to the measured change in power of input signal to provide an output amplified signal having a substantially constant power for one or more changes in the power of the input signal.

Abstract: The invention refers to a method for operating an amplifier with a first amplifier stage (A1) and a second amplifier stage (A2), pumped by a single pump light source (11) generating a primary pump signal (SPUMP), which is split into first pump signal (S1) and a second pump signal (S2) according to a variable splitting factor (?) for pumping the first amplifier stage (A1) and the second amplifier stage (A2) respectively. The splitting factor (?) is varied to achieve an optimized noise figure.

Abstract: An optical amplifier includes a semiconductor optical amplifier which has a gain that changes in accordance with a wavelength of input light and which generates a noise light power having different levels in accordance with a drive current, a detector that detects an optical power branched from output light of the semiconductor optical amplifier, and a controller that controls supply of the drive current based on the optical power such that an output light power of the semiconductor amplifier is a sum of a target signal light power and the noise light power.

Abstract: An optical amplifier includes an input port, an output port, an amplification medium, a light source, a monitor, and a controller. The amplification medium with which doped an rare-earth element for optical amplification is allocated on an optical path between the input port and the output port. The light source supplies the amplification medium with an excitation light. The monitor monitors a total power of an optical signal of each wavelength according to a monitor period which is longer than a transient response time of the amplification medium. The controller controls the light source so that a power of the excitation light is constant when a monitor value of the monitor is equal to or smaller than a predetermined threshold value and controls the light source so that an optical gain in the amplification medium is constant when the monitor value is larger than the predetermined threshold value.

Abstract: There is provided an optical amplifier including a pump light source to generate a pump light being capable of changing a wavelength thereof, a first rare earth doped medium to amplify an input signal light by using the pump light generated by the pump light source, a second rare earth doped medium to amplify the input signal light output from the first rare earth doped medium by using a residual pump light that is a portion of the pump light generated by the pump light source, and a wavelength controller to control a wavelength of the pump light generated by the pump light source, based on an input level of the input signal light.

Abstract: Exemplary embodiments of the invention are drawn to a method and apparatus for the differentiation of power and channel count changes in optically amplified links. Additionally, configuration of a corresponding optical amplifier can be based on the determination of the power and channel count changes.

Abstract: An optical amplifier has a pump and an “anti-pump” for reducing a variation of the amplifier gain with the input optical power. The wavelength of “anti-pump” light is longer than the wavelength of the optical signal being amplified, so that the optical signal serves as a pump for the “anti-pump” light, whereby an optical loss variation with the signal power at the signal wavelength is created, which reduces optical gain variation with the signal power. To compensate for gain loss due to the anti-pump light, two and three stages of amplification can be used.

Abstract: An optical demultiplexer (13, 30) for wavelength division multiplex WDM optical radiation comprising a plurality of wavelength channels (Ch1 . . . Ch16) spaced over a wavelength spectrum said demultiplexer being for separating the WDM radiation into individual wavelength channels is described. The demultiplexer comprises a first demultiplexer (12) for dividing the W-DM radiation into a plurality of sub-bands (Ch1 . . . Ch4, Ch5 . . . Ch8, Ch9 . . . Ch12, Ch13 . . .

Abstract: A multi-wavelength light amplifier includes a first-stage light amplifier which has a first light amplifying optical fiber amplifying a light input, a second stage light amplifier which has a second light amplifying optical fiber amplifying a first light output from the first-stage light amplifier, and an optical system which maintains a second light output of the second-stage light amplifier at a constant power level. The first-stage and second-stage light amplifiers have different gain vs wavelength characteristics so that the multi-wavelength light amplifier has no wavelength-dependence of a gain thereof.

Abstract: A Self-adapting feed forward control apparatus in an optical amplifier includes a feed forward controller for collecting target output power (Pout) and controlling drive current of a pump laser in the optical amplifier; a feedback controller for calculating target output power (Pt) and collecting actual output power (Pout), calculating deviation between (Pt) and (Pout), and controlling drive current of the pump laser; and a parameter estimator for collecting power target, output power and summation of output signal of the feed forward controller and feedback controller, and estimating the feed forward parameter and updating the parameter of the feed forward controller. The apparatus can automatically correct the feed forward control parameters according to the variation of EDFA parameters due to environmental condition changes or device aging.

Abstract: A controller for reducing a transient variation of gain of an optical amplifier is disclosed. The controller includes a control circuit adapted to generate an electrical signal mimicking optical gain transient variation upon an abrupt change in input loading conditions. The electrical signal is applied to a variable optical attenuator disposed downstream of the active optical fiber of the optical amplifier. The control circuit can be realized in a variety of ways, but preferably it includes a logarithmic amplifier and a high-pass filter sequentially connected. The logarithmic amplifier is connected to an input tap/photodetector, and the high-pass filter is connected to the variable optical attenuator.

Abstract: An optical amplifier including: a first amplifying unit amplifying an input light by utilizing a first excitation light and thereby outputting a first amplified light; a second amplifying unit amplifying the first amplified light by utilizing a second excitation light and thereby outputting a second amplified light; and a control unit detecting a first absorption rate of the first excitation light and a second absorption rate of the second excitation light, and controlling a level of the first excitation light and a level of second excitation light based on the first absorption rate and the second absorption rate. The first absorption rate corresponds to a ratio of the first excitation light absorbed in the first amplifying unit, and the second absorption rate corresponds to a ratio of the second excitation light absorbed in the second amplifying unit.

Abstract: An optical amplifier provided in a repeater station of an optical transmission system is proposed. The optical amplifier amplifies an signal light and performs ALC of output power by means of a variable optical attenuator (VOA). The optical amplifier receives a difference between a target output value and measured output value of an upstream optical amplifier as an expected control volume, and updates a target attenuation value for the VOA in accordance with a current target attenuation value set to the VOA for ALC, a difference between its own target output value and measured output value, and the expected control volume. The target attenuation value is updated at intervals of time exceeding output convergence time by ALC. The difference between the target output value and measured output value of the optical amplifier is adopted as the expected control volume for a downstream optical amplifier.

Abstract: The specification describes an improved approach to suppressing fast transients in optical amplifier systems. The approach relies on operating the amplifier in an automatic power-mode control with an extra loss component. It is applicable to optical amplifiers based on rare earth amplifier media, such as erbium doped fiber amplifiers (EDFAs).

Abstract: According to a WDM optical transmission system of the present invention, wavelength numbers information of a WDM signal light output from an upstream side optical amplifying unit to a transmission path fiber, and signal output level information thereof are transmitted to a downstream side optical amplifying unit utilizing a supervisory control light. In the downstream side optical amplifying unit, a loss (span loss) in the transmission path fiber is computed using the upstream side signal output level information and downstream side signal input level information, so that a gain to be set for a downstream side optical amplifier is calculated based on the computed loss, and also, the gain is corrected based on a difference between a target value of the signal output level computed using the wavelength numbers information and an actual measurement value thereof, so that the optical amplifier is controlled in accordance with the post-corrected gain.

Abstract: An optical amplifier includes a detecting section configured to detect a part of an input optical signal from a first node on an input side optical fiber; and a rare earth element doped optical fiber amplifier configured to amplify a remaining part of the input optical signal supplied from the input side optical fiber by using an excitation optical signal supplied from a second node and to output the amplified optical signal as an output optical signal to an output side optical fiber. A control unit controls the excitation optical signal based on the detected part of the input optical signal by the detecting section without real time control based on the output optical signal.

Abstract: A system and method for controlling the gain of an optical amplifier receiving one or more optical input signal channels at a first end include a source for generating a gain control signal, which is input to the optical amplifier at the opposite end to the input signal channels. The gain control signal is generated at a power level that produces stimulated Brillouin scattering (SBS) in the optical amplifier.

Abstract: An optical amplifier provided in a repeater station of an optical transmission system is proposed. The optical amplifier amplifies an signal light and performs ALC of output power by means of a variable optical attenuator (VOA). The optical amplifier receives a difference between a target output value and measured output value of an upstream optical amplifier as an expected control volume, and updates a target attenuation value for the VOA in accordance with a current target attenuation value set to the VOA for ALC, a difference between its own target output value and measured output value, and the expected control volume. The target attenuation value is updated at intervals of time exceeding output convergence time by ALC. The difference between the target output value and measured output value of the optical amplifier is adopted as the expected control volume for a downstream optical amplifier.

Abstract: An automated optical transport system is provided which provides for automatic discovery of system components, automatic inventory of system components, automatic topology detection, automatic provisioning of channels, and automatic characterization and tuning of system components and fiber. The invention provides automation capability through inclusion of management card capabilities at each station which communicates through a reverse propagating service channel. Dynamic and propagation direction independent segments are provided in conjunction with a token-based scheme to repeatedly tune, update and monitor the transport system.

Abstract: An optical transmission apparatus for amplifying and relaying a wavelength-division-multiplexed optical signal includes (1) a variation-detecting unit which detects varying speed of input power of the wavelength-division-multiplexed optical signal and compares the varying speed with a set value, (2) an optical amplifying unit which amplifies the wavelength-division-multiplexed optical signal at a fixed amount of amplification, (3) a variable optical attenuating unit which variably attenuates the wavelength-division-multiplexed optical signal, (4) and a controlling unit which controls attenuation amount of the variable optical attenuating unit in accordance with the varying speed.

Abstract: A wavelength division multiplexing (WDM) device, an optical leakage prevention method, and a WDM communication system are disclosed. The WDM device includes a level adjusting unit for receiving an optical signal, for adjusting the optical power level of the received optical signal, and for outputting the level-adjusted optical signal; and a controlling unit for analyzing the optical power level of the optical signal output from the level adjusting unit, for controlling the level adjusting unit so that the optical power level of the output optical signal stays at a constant level, and for transitioning to an “off-state” when the optical power level of the output optical signal becomes less than a predetermined disconnection-detection threshold so that the level adjusting unit gives a predetermined attenuation to the input optical signal.

Abstract: In a wavelength-division-multiplexing optical transmission system in which optical-node apparatuses that perform relay transmission of wavelength-division-multiplexed light are located at specified nodes in a main optical transmission path, an optical amplifier switches level control to constant-gain control when there is a notification of a change in the number of multiplexed wavelengths, and then after a specified amount of time restarts level control so that the level becomes a target level that corresponds to the actual number of wavelengths.

Abstract: A transmission apparatus designed to be capable of monitoring faults which occur between the input stage of an optical multiplexer and the input stage of an optical amplifier, appropriately switching between automatic gain control and automatic level control, and outputting signal lights with appropriate optical power, without using a spectrum analyzer. The optical multiplexer combines the wavelengths of a plurality of signal lights. The optical amplifier is connected at the latter stage of the optical multiplexer, and operates in the automatic gain control mode or in the automatic level control mode, the automatic gain control mode maintaining a constant gain for wavelength-multiplexed signal light, the automatic level control mode maintaining constant output power for the wavelength-multiplexed signal light.

Abstract: An optical amplifying apparatus which includes an optical amplifier, an optical attenuator and a controller. The optical amplifier amplifies a light signal having a variable number of channels. The optical attenuator passes the amplified light signal and has a variable light transmissivity. Prior to varying the number of channels in the light signal, the controller varies the light transmissivity of the optical attenuator so that a power level of the amplified light signal is maintained at an approximately constant level that depends on the number of channels in the light signal prior to the varying the number of channels. While the number of channels in the light signal is being varied, the controller maintains the light transmissivity of the optical attenuator to be constant.

Abstract: In an optical amplifier of the invention, a first variable optical attenuator is provided between a fore-stage optical amplification unit and a post-stage optical amplification unit, and a second variable optical attenuator is also provided on the output side of the post-stage optical amplification unit. When a signal light input level of a WDM light inputted to an input port is lower than a base point level, an attenuation amount of the first variable optical attenuator is not increased (basically minimized), and the control which increases the attenuation amount of the second variable optical attenuator is performed corresponding to the increase in signal light input level. On the other hand, when the signal light input level is higher than the base point level, the attenuation amounts of both the first variable optical attenuator and the second variable optical attenuator are controlled according to the signal light input level.

Abstract: A method for cost-effective optical transmission with fast Raman tilt or other transient event control uses a combination of Erbium-doped fiber amplifiers (EDFAs) and Raman fiber amplifiers (RFAs), where EDFAs are used as the primary optical amplifiers to compensate the span loss while the RFA (advantageously a forward-pumped RFA) is used only in some specific spans with a feed-forward control circuit serving as a fast Raman tilt transient compensator, the RFA also serving as an optical amplifier. A long haul optical transmission system using feed-forward controlled RFA's periodically spaced along its length, for example, when add-drop multiplexing is used, makes full use of the economics of EDFAs and the fast tilt transient control capability of a RFA enabled by an adjustable speed feed-forward or feed-back control technique.

Abstract: A bidirectional amplification system and method are disclosed. A single optical line amplifier and isolation loss filters are used to amplify signals in both the east and west directions with sufficient gain along a fiber.

Abstract: Optical amplifying method and apparatus are proposed. Constant gain amplifiers operate such that the output power of the amplifier generally tracks the input power. However, optical systems are not perfect and the input to the optical amplifier stage includes not only the desired signal, but also includes accumulated effects of the imperfections. The imperfections include losses of the fiber sections, variations in laser powers, and drifts. Thus, simple amplification not only amplifies the desired signal, but also amplifies accumulated imperfections. Such imperfections occur over time and are generally small in magnitude. By operating the amplifier such that amplification of small variations is suppressed while allowing for tracking of large input variations, amplifying the accumulated imperfections is minimized.

Abstract: There are provided an ASE correction unit which corrects control errors regarding either or both of the gain and the output level of the optical amplifier, which control errors are generated due to the ASE, and an ASE correction controller which controls the correction of the control errors by these ASE correction unit based on a predetermined time constant. Accordingly, the ASE correction errors of the optical amplifier, which performs the ASE correction are suppressed, and stabilization of the output signal light level and the optical amplification gain at the time of changes of the wavelength number can be attained.

Abstract: An optical transmitting apparatus includes a variable optical attenuating unit for attenuating signal light variably, an optical amplifying unit for amplifying the signal light, and a looped optical circuit for returning the signal light from the optical amplifying unit to the variable optical attenuating unit. The variable optical attenuating unit further attenuates the returned signal light variably.

Abstract: A multimode fiber receiver includes a multimode collimator, a multimode fiber optic amplifier and a detector. The collimator receives incoming signals and provides the signals to the amplifier. The amplifier includes plural amplification stages, a limiter, a tunable narrow band filter and a microcontroller. The amplification stages each include a gain element and a noise filter. The limiter receives the amplified signals and limits the energy of those signals. The optical signals subsequently traverse the narrow band filter including an adjustable pass band to provide desired signals to the detector. The microcontroller measures the energy of the incoming and output signals to control the limiter, amplification stages and/or narrow band filter in order to produce signals within the dynamic range of a particular application. The multimode fiber optic amplifier and/or receiver of the present invention is preferably utilized within an optical communication unit.

Abstract: An optical amplifier of the present invention comprises: first and second optical amplifying sections connected in series to each other between an input port and an output port; a first variable optical attenuator arranged on a former stage of the first optical amplifying section; a second variable optical attenuator arranged between the first and second optical amplifying sections; an optical amplification control section that controls the first and second optical amplifying sections; and an optical attenuation control section that controls the first and second variable optical attenuators.

Abstract: In an optical amplifying device, an optical beam passes multiple times through a grazing-incidence bounce amplifier, accessing different parts (G1,G2) of the gain region on each transit. This provides improved characteristics in beam quality, with higher power scalability. The multipass configuration can operate as a high gain amplifier device and, with the addition of suitable feedback such as reflectors (M1-M4), as a laser oscillator to provide an optical source.

Abstract: A multimode fiber receiver includes a multimode collimator, a multimode fiber optic amplifier and a detector. The collimator receives incoming signals and provides the signals to the amplifier. The amplifier includes plural amplification stages, a limiter, a tunable narrow band filter and a microcontroller. The amplification stages each include a gain element and a noise filter. The limiter receives the amplified signals and limits the energy of those signals. The optical signals subsequently traverse the narrow band filter including an adjustable pass band to provide desired signals to the detector. The microcontroller measures the energy of the incoming and output signals to control the limiter, amplification stages and/or narrow band filter in order to produce signals within the dynamic range of a particular application. The multimode fiber optic amplifier and/or receiver of the present invention is preferably utilized within an optical communication unit.

Abstract: An amplification medium simulation apparatus comprises a basic data retaining unit 21, an input signal beam information retaining unit 22, and a simulation executing unit 31 approximating and calculating an output signal beam power at each signal beam wavelength outputted from the amplification medium involving a fluctuation in ion population at the metastable energy level in the amplification medium due to input of the input signal beam, by using contents retained in the basic data retaining unit 21 and the input signal beam information retaining unit 22, and outputting a result of calculation as a result of simulation of performance of the amplification medium.

Abstract: A method of controlling an optical wavelength division multiplexing transmission apparatus achieves stable wavelength division multiplexing optical transmission by switching a control mode of an optical amplification section in accordance with an input state of optical signals of various wavelengths. Accordingly, the method involves, upon startup of the optical wavelength division multiplexing transmission apparatus, initial setting of information such as the wavelengths being used and the number of wavelengths being used, setting the amount of optical attenuation for each wavelength to a maximum value, and setting an optical amplification unit to ALC.

Abstract: An optical amplifier includes first and second optical amplifier units, a variable optical attenuator optically coupled between the first and second optical amplifier units, a first control unit to control gains of the first and second optical amplifier units based on an input of the first optical amplifier unit and an output of the second optical amplifier unit, and a second control unit to control an attenuation quantity of the variable optical attenuator based on the input and an output of the first optical amplifier unit and an input and the output of the second optical amplifier unit.

Abstract: A broad-band light source has a reduced tendency to oscillate and has high efficiency. The broad-band light source comprises (a) an optical waveguide that comprises a optical active element to generate an ASE lightwave when a pumping lightwave is supplied, that outputs an ASE lightwave in a first wavelength band from its first end, and that outputs an ASE lightwave in a second wavelength band from its second end, (b) a pumping lightwave-supplying means for supplying a pumping lightwave to the optical active element, and (c) a lightwave-combining means that receives the ASE lightwave in the first wavelength band, that receives the ASE lightwave in the second wavelength band, that combines the received ASE lightwaves, and that outputs the resultant ASE lightwave.