Abstract: A method for pre-emphasising transmitted signals in channels for multiplex signals along a transmission path comprising supply and/or branch points is provided. According to the method, relative degradations of the signal-to-noise intervals between transmitted signals via any category or group of channels—i.e. express and add or drop channels or add-drop channels are taken into account. A point-to-point link and for transparent optical networks may be used. To this end, the average signal powers of different channel groups are set relative to one another in order to obtain predetermined signal-to-noise intervals for each group. In addition, the signal-to-noise intervals within a channel group are equalized at their termination points. Regulation protocols for controlling the pre-emphasising steps are provided.

Abstract: A signal identification method for efficiently identifying Dense Wavelength Division Multiplexing (DWDM) channel modulation formats, signal powers, and center frequency detuning of signals that may be used in conjunction with telecom-grade monitoring equipment. The method utilizes least-square curve fitting estimates applied to a set of curves, each curve is characteristic of a modulation format and rate. For each least-square estimate an error value is calculated, and a curve fit with the least error is selected as the identified signal format for a signal.

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 an optical communication network, optical communication nodes exchange information detailing power level variations to support management and administration of optical communications. This exchange of information permits nodes to determine aggregate power level variations over light paths to support operations such as selection from available light paths and configuration of optical communication characteristics.

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: Methods are described for preemphasizing an optical multiplex signal that comprises a plurality of signals having different wavelengths, which are transmitted by a transmitter to a receiver. Power levels for the signals are set at the transmitter and measured at the receiver. A mean power level for the transmit-side signals is ascertained. New signal power level values are ascertained from the current power levels of the signals at the transmitter and at the receiver and set on the transmit side such that signal-to-noise ratios for all signal are approximately equalized at the receiver. In order to make more precise settings for the preemphasis, mean gain values and mean attenuations are ascertained from the sum power levels for the multiplex signal measured at the input and at the output of each amplification section and incorporated together with an effective noise figure into the process of ascertaining the new signal power level values.

Abstract: An optical transmitter has a resonance wavelength characteristic that varies with the refractive index of the optical transmitter. The optical transmitter receives a narrow band injected wavelength signal from an incoherent light source. The controller substantially matches a resonant wavelength of the optical transmitter to the wavelength of the injected wavelength signal by changing the refractive index of the optical transmitter to substantially match the resonant wavelength of the optical transmitter and the wavelength of the injected wavelength signal. A detector measures a parameter of the optical transmitter to provide a feedback signal to a controller to determine when the resonant wavelength of the optical transmitter and the wavelength of the injected wavelength signal are substantially matched.

Abstract: A method of transmitting data can include pre-emphasizing data for transmission by a transmitter over a transmission line based on an error feedback signal provided to the transmitter from a receiver of the pre-emphasized data.

Abstract: A device (D2) is dedicated to controlling degradation parameters associated with signals on channels with different wavelengths, possibly arranged in bands of channels, and transmitted by transmission lines (Lj) connecting nodes (Ni) of a transparent optical communication network. The device includes processing means (PM2) adapted, in the event of transmission of signals of at least two channels or bands of channels by at least one transmission line (Lj), to measure for each of said channels or each of said bands of channels, firstly, the value of a parameter representative of the degradation of the signals on the corresponding line (Lj) and, secondly, taking account of said measured values, a power profile to be imposed on the signals so that they have predetermined degradation parameter values.

Abstract: A light beam which is used for transmitting a wavelength division multiplex signal is guided to a Bragg grating via an adjustable mirror. According to the angle of incidence of the light beam relative to the longitudinal axis of the Bragg grating, different transmission characteristic curves having different gradients are produced. As a result thereof, scattering of the wavelength division multiplex signal can be compensated. A second controllable mirror enables the damping to be adjusted. A control device effects a rapid correction of the scattering after data signals are connected or disconnected.

Abstract: An optical intensity control system for use with an optical switch providing individual signal paths between input and output ports. The system has a optical splitters connectable to output multiplexers of the switch and also has variable optical intensity controllers (VOICs) for insertion into the individual signal paths. The VOICs individually control the intensity of optical signals present in the signal paths in accordance with intensity control signals. An equalizer is connected to the splitters and to the VOICS, for producing an estimate of the optical power of each individual switched optical signal and generating the intensity control signals. The equalizer is adapted to controllably isolate individual switched optical signals.

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: 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: An optical transmission apparatus includes a demultiplexer for separating wavelength-division multiplexing light received from a first optical transmission line into signals of different wavelengths to transmit the signals to an outside and a multiplexer for multiplexing signals of different wavelengths received from the outside to transmit multiplexed signals to a second optical transmission line. An input check unit is provided for monitoring a power level of a signal separated by the demultiplexer and for providing an output indicative thereof. An output adjuster is provided for intercepting a signal from the outside so as to inhibit receipt of the signal from the outside by the multiplexer depending on the output of the input check unit.

Abstract: An optical node apparatus according to the present invention amplifies a WDM signal light input to an input port, and thereafter, branches the amplified WDM signal light by an optical branching coupler to send the branched lights to first and second optical paths, and selects the light propagated through the first optical path by an optical switch to amplify the selected light by a post-amplifier, thereby outputting the amplified light from an output port, when the optical node apparatus is operated as an optical amplification repeating node. When the operational state is upgraded to an optical add/drop multiplexing node, an OADM section is connected between a set of connecting ports on the second optical path, and the adjustment of the OADM section is performed utilizing the WDM signal light branched by the optical branching coupler, and thereafter, the switching of the optical switch is performed to select the light on the second optical path side.

Abstract: A transmitter (11) emits a single wavelength optical signal and transmits this as a wavelength channel (13) in a compound multiplex signal through the WDM network. The receiver (12) selects the single wavelength optical signal (21) from the compound multiplex signal using a band-pass filter. A wavelength fit detector (15) determines a feedback signal by correlating variations of the amplitude of the received signal with variations of the traffic density. This feedback signal is then returned to the transmitter (11) via a back channel (16) and serves to tune the wavelength of the single wavelength optical signal.

Abstract: A WDM optical transmission system of the invention has a configuration where WDM light generated at a wavelength multiplexing station is transmitted via a plurality of stations such as optical add-drop stations, arranged on an optical transmission line, and control of the power of the optical signals of respective wavelengths included in the WDM light is performed in the wavelength multiplexing station and the optical add-drop stations. A device is provided which communicates between stations, optical signals including information related to the control state of the optical signal power in each station, so that after control of the optical signal power at an upstream station is complete, control of the optical signal power at the downstream station is executed. As a result, stable control in respective stations can be performed even at the time of increasing or decreasing the number of wavelengths.

Abstract: A method, system and storage medium for monitoring power control loops in an optical communication network. The method includes polling network elements to obtain power management information for the network elements. A set of power management rules is selected based on the power management information along with network configuration, channel types, etc. The power management rules are applied to determine the validity of open and closed power control loop in the network elements.

Abstract: Apparatus and method for equalizing a multiplicity of amplifier optical output signals comprised of a combined broadcast optical signal and a narrowcast optical signal having different bands of wavelengths of light by adjusting the power output level of at least one the signals in response to an amplified sample of the signal. A light switch or attenuator and a sensor for determining whether a transmission fiber is in place is connected to each of the multiplicity of optical output signals to allow the optical output signals to be turned on and off for maintenance and repair.

Abstract: Various methods, systems, and apparatuses is described in which a passive-opticalnetwork includes a first multiplexer/demultiplexer, a second multiplexer/demultiplexer, a wavelength tracking component, and a transmission wavelength controller. The first multiplexer/demultiplexer is located in a first location. The second multiplexer/demultiplexer is located in a second location remote from the first location. The wavelength tracking component determines the difference between the transmission band of wavelengths of the first multiplexer/demultiplexer and the second multiplexer/demultiplexer to provide a control signal to match the transmission band of wavelengths of the first multiplexer/demultiplexer and the second multiplexer/demultiplexer. The transmission wavelength controller alters an operating parameter of the first multiplexer/demultiplexer based on the control signal to control the transmission band of wavelengths of the first multiplexer/demultiplexer.

Abstract: The invention relates to a method for easily and rapidly preemphasizing an optical multiplex signal transmitted by an emitter to a receiver consisting wherein signal-to-noise ratios are equalized by means of simple measurement or new adjustment of signal power on the bandwidth of the optical multiplex signal, at least in the receiver, instead of measuring the noise output power or the signal-to-noise ratio. Said invention is based on a balance of the signal-to-noise ratios which are authorized by a transmitting system, in which the spectral influences of gain profiles, noise effects and dampings are taken into consideration. In particular, when DWDM transmission techniques are applied, in which adjacent channel spacings of the optical multiplex signal are very low, the inventive method makes it possible to use a small number of sensitive and high-resolution measuring instruments for pre-emphasis control.

Abstract: A sub signal modulation apparatus, with the intention of stabilized transmission of a sub signal superimposed on main signal light irrespective of the intensity of the main signal light when used in a general-purpose main signal transmitter, including a sub signal outputting unit; a variable optical attenuator for variably attenuating main signal light, into which the main signal has been modulated, at a response speed lower than ½ of a speed of the main signal; an attenuation determining unit for determining, in accordance with the sub signal output from the sub signal outputting unit, an attenuation of the variable optical attenuator for the main signal light; and a stabilizing controller for controlling the attenuation determining unit such that an amplitude of the attenuation of the variable optical attenuator is stabilized to have a constant ratio to a mean intensity of the main signal light.

Abstract: WDM optical tranmsmission equipment with redundant configuration includes a plurality of tranmitters. Each tranmitter includes active and standby panels including active and standby optical transmission circuits respectively having active and standby attenuators for controlling an attenuation amount of each output of the active and standby optical transmission circuits; and a coupler combining the outputs of the active and standby attenuators.

Abstract: There is provided a method of, and apparatus for, regulating radiation component (wavelength channel) power in a wavelength division multiplexed (WDM) optical communications system (10). The system (10) comprises a plurality of nodes (20) interconnected through optical waveguides (30, 40) (optical fibers). The method is characterised by: passing one or more tokens (300) around the system from node to node; adjusting nodal settings (150, 170), such as optical attenuation, applied at each node to regulate the power of WDM radiation components at the node in response to receiving one or more tokens; and repeating the method until WDM radiation component power within the system is substantially regulated.

Abstract: An optical control monitor and a method for adjusting for changes in optical signals transmitted through an optical network. The method comprises the steps of transmitting a set of optical signals through a network, each of the optical signals having a respective wavelength; and tracking changes to said set of signals by passing each of the signals through a filter having a bandpass function, and dithering the filter bandpass about the wavelengths of each of said set of signals to generate filter output signals. The filter output signals are used to adjust the network or the set of optical signals to compensate for said changes.

Abstract: An optical transmitter system supplies a plurality of different wavelength optical radiation components to a transmission element which, in operation, is connected to the transmitter system for conveying the different wavelength radiation components to a respective receiver. The transmitter system detects a loss of a wavelength radiation component at the respective receiver. The supply of the wavelength component is interrupted in response to a detection of loss of the wavelength component at the receiver. A timing circuit provides respective restart times which differ one to another for the wavelength radiation components. The supply of the wavelength component is restarted, following an interruption, at the restart time provided by the timing circuit.

Abstract: A wavelength converter for binary optical signals includes an interferometer structure (110) for generating an output signal by modulating a received local signal (LS) according to the modulation of a fUrther received first input signal (IS 1). When such interferometer structures (110) are operated in a standard mode it is known in the art to control the power of the input signal such that the extinction ratio of the output signal is kept minimal. The invention also controls the power of the input signals to achieve the minimal extinction ratio when the wavelength converter and in particular the interferometer structure (110) is operated in a differential mode receiving two input signals.

Abstract: An optical network terminal, which includes an optical transmitter, monitors the status of the optical transmitter, such as the output or the power consumption of the optical transmitter, to determine when the optical transmitter is illegally transmitting. When an illegal transmission is detected, the optical network terminal removes power from the optical transmitter.

Abstract: An optical transmitter including a multi-lambda source to output injection light consisting of a plurality of injection wavelengths in channels, a circulator having a first port, a second port, and a third port, the circulator receiving the injection light at the first port, and outputting the received injection light to the second port, and further receiving signal light at the second port, and outputting the received signal light to the third port, an arrayed waveguide grating having a multiplexing port connected to the second port of the circulator, and a plurality of demultiplexing ports, spectrum-slicing injection light received from the circulator at the multiplexing port into a plurality of injection channels, and outputting the injection channels to the demultiplexing ports and further receiving and multiplexing a plurality of signal channels at the demultiplexing ports, into a signal light, and outputting the signal light to the multiplexing port, and a plurality of reflective semiconductor optical a

Abstract: A method and apparatus for controlling bias and alignment in an optical signal transmitter for providing intensity modulation and DPSK modulation to an optical signal, e.g. in an RZ-DPSK modulation format. Output power in dither signals applied to the bias signals may be detected by a low speed photodetector. One or more of the bias signals may be adjusted in a low speed control loop in response to an error signal obtained by mixing the detected signal with the low frequency dither signals.

Abstract: An optical receiver is disclosed comprising an erbium-doped fiber amplifier (EDFA) that is coupled to a photodiode and transimpedance amplifier without filtering output light signal in the EDFA. Optionally, a clock/data regenerator can be coupled to the electrical output of the transimpedance amplifier for compensating for noise distortion and timing jitter for affecting the control loop feeding back for adjusting the electrical current into a pump laser of an optical pre-amplifier. Furthermore, the optical receiver of the present invention can also be implemented in a transponder.

Abstract: An apparatus for selectively adjusting power levels of component signals of a wavelength division multiplexed signal. The apparatus comprises a first filter and a second filter. The first filter modulates the component signals according to a static attenuation profile, thereby providing coarsely modulated component signals. The second filter is coupled to the first filter to receive the coarsely modulated component signals and to modulate the coarsely modulated component signals according to a dynamic attenuation profile, thereby providing finely modulated component signals.

Abstract: Optical communication apparatuses and optical communication methods are provided. According to one aspect, an optical communication apparatus includes a communication path configured to communicate a first signal; a signal generator configured to provide a second signal; a combiner configured to combine the first signal with the second signal to provide a composite signal; and a light source coupled with the combiner and configured to receive the composite signal and to output an optical signal corresponding to the composite signal to an optical conduit, wherein the signal generator is configured to monitor the application of the optical signal to the optical conduit and to alter the second signal responsive to the monitoring.

Abstract: An improved photonic switch having optical amplification is described. Signals are amplified before they are switched, after they are switched, or both before and after they are switched. The optical amplification compensates for fixed losses within the switch and transmission system, or provides output power equalization. The photonic switching system includes a demultiplexer for dividing incoming light into different wavelengths or wavebands. The different signals are then supplied to optical amplifiers. The amplifiers amplify the optical signals before supplying them to the optical switch core. Once in the optical switch core, the signals are switched as desired to specified output nodes, then multiplexed back together to provide an output signal from the photonic switching system. In some systems amplification is further provided on the output side.

Abstract: An optical transmission equipment in an optical communication system interconnecting two optical transmission equipment sets by a main transmission line and a backup transmission line. An optical amplifier amplifies and outputs optical signals from one transmission line in use, interconnecting the optical transmission equipment concerned with neighboring upstream optical transmission equipment, and outputs the optical signals including a signal component and a noise component. A controller controls an optical signal level so that a signal component in the optical signal reaches a predetermined level.

Abstract: The present invention is to provide method and apparatus for adapting a GBIC module to an Ethernet switch capable of outputting one of different voltages in which in a case of the GBIC module coupled to the Ethernet switch, a DC converter of the GBIC module is adapted to lower an input voltage thereof supplied by the Ethernet switch prior to boosting the lowered voltage to an operating voltage required by a GBIC logic circuit of the GBIC module without confirming whether the input voltage has the same value as the operating voltage. Thus, the present invention can prevent the GBIC module from not working due to low input voltage or being damaged due to high current when the GBIC module is coupled to the Ethernet switch.

Abstract: A reconfigurable optical add-drop multiplexer is disclosed that enables Optical Multiplex Section (OMS) shared protection rings. The ROADM comprises a first optical supervisory module, coupled to a first amplifier module, which in turn is coupled to a first broadcast and select module, where the first broadcast and select module is coupled to both a first multiplexer/demultiplexer module and the first optical supervisory module. Each optical supervisory module has an optical tap for tapping a fraction of an outgoing OMS signal that is fed back or looped back to a 2×1 optical switch in the optical supervisory module.

Abstract: A channel-growth plan for an optical transmission system selects channels such that the transients that result in the channels that survive a network failure, such as an upstream fiber cut, are either minimized or effectively handled by some transient-control technique. In one embodiment, the growth plan may try to keep post-transient surviving channel total power gain equal to the pre-transient total power gain. Alternatively, the growth plan may try to distribute the surviving channels uniformly over the pre-transient channel-frequency range. Other manifestations are to keep (1) the average power of the surviving channels substantially equal to the average power of the pre-transient channels or (2) the average power of the post-transient surviving channels substantially equal to the power level of a specified channel. Transient-control can be balanced with conventional low-cost and high-performance goals to provide an effective hybrid channel-growth plan.

Abstract: An optical transmission system including an optical transmitting device and an optical receiving device. The optical transmitting device includes a data signal splitting section for splitting data signal information into at least two parts and generating at least two electrical signals having different center frequencies and bands, a frequency multiplexing section for performing frequency multiplexing for the at least two electrical signals, and an electrical-to-optical conversion section for converting the frequency-multiplexed signal to an optical signal and sending it to an optical transmission path. The optical receiving device includes an optical-to-electrical conversion section for converting the optical signal to a frequency-multiplexed signal, a band demultiplexing section for demultiplexing the frequency-multiplexed signal to obtain at least two electrical signals, and a data signal recovering section for recovering the data signal based on the at least two demultiplexed electrical signals.

Abstract: A pre-emphasis control method automatically and appropriately performs the pre-emphasis of each wavelength in a wavelength division multiplexing communications system. Before instructing pre-emphasis for a transmitting unit, the optical power of an optical signal of each channel (wavelength) is increased/decreased by a predetermined value, and it is determined for each channel whether or not the difference between a Q value when the optical power is large and a Q value when the optical power is small, is larger than 0. Depending on the determination, that is, if the difference is larger than 0, then it is determined that the channel belongs to a linear area, and if the different is equal to or smaller than 0, then the channel belongs to a nonlinear area. If the Q value of each channel is to be improved by the pre-emphasis, then the optical power is increased for the channel in the linear area, and decreased for the channel in the nonlinear area.

Abstract: A laser apparatus is disclosed combining polarized light beams from two optical emitters into a combined beam of light with controllable degree of polarization (DoP). The laser apparatus includes a polarization combiner for combining the polarized beams into the combined beam, an optical tap for separating out a portion of the combined beam, and a photodetector electrically coupled to a laser controller for providing a feedback signal. The controller distinctively modulates the polarized radiation of each of the emitters, detects modulation signals in the photodetector output and adjusts an output power ratio of the optical emitters for maintaining the DoP of the combined beam at a pre-determined level. The invention can be used for minimizing the DoP of pump radiation in Raman and EDFA pump laser modules combining multiple pump laser diodes.

Abstract: A method and system for multi-level power management in an optical network is provided. They include three levels of power equalization. The first level of power management equalizes the powers of channels in a band of channels. The second level of power management equalizes the average powers of bands of channels on a fiber. The third level of control equalizes the powers of bands of channels on working and protection fibers for a path in the optical network. As a result, this multi-level power management in the network provides a dynamic, automatic method for the network to adjust to changing operating conditions and configurations and to maintain relatively stable network powers. Each level of power management may be implemented jointly or independently, and operates autonomously so that, for example, one modification comprises continuous first level control and only periodic second level control.

Abstract: The multi-channel optical transmitter is composed of a tunable optical signal source, an optical multiplexer and an intensity reducer. The tunable optical signal source includes a tunable laser, and additionally includes an optical signal output through which it outputs an optical signal to one of the inputs of the optical multiplexer. The intensity reducer is for reducing the intensity of the optical signal output by the optical signal source during tuning of the tunable laser. The intensity reducer prevents the tunable optical signal source from injecting high levels of noise into the channels during tuning of the tunable optical signal source.

Abstract: An optical level calculator calculates optical powers of individual wavelengths of a through wavelength division multiplexed signal based on an input level monitor, network information, and insertion loss information 5, and obtains an optimum level for an add signal. An optical level controller controls a power of the add optical signal to the optimal level based on the calculated result, and multiplexes the through wavelength division multiplexed signal and the add optical signal.

Abstract: A terminal apparatus by which, even where BER data, for example, of an optical signal of an existing wavelength cannot be utilized, the optical output powers of the existing wavelength and an extension wavelength can be adjusted in a short period of time while eliminating quality degradation of the existing circuit. The terminal apparatus includes a level controlling section for controlling a total optical output power of an existing wavelength signal light and an extension wavelength signal light to a fixed level, a monitoring unit capable of monitoring the optical output power for each wavelength, and a controller for controlling the optical output power of the extension wavelength signal light so that the optical output power of the existing wavelength signal light monitored by the monitoring unit may not be lower than a minimum permissible optical output power.

Abstract: An optical communication device, and related method, are provided for providing a tailored, spectrally non-uniform gain over a broad spectrum. In particular, the optical communication device includes an optical amplifier having a dynamic gain equalization (DGE) circuit that adjusts the gain spectrum of the optical amplifier to provide uniform gain, at a desired level, within individual channel bands in accordance with the data rates of channels in those bands. Accordingly, the overall spectrum has a “stepped” profile with higher gain values for high data rate channels and lower gain values for lower rate channels. As a result, a WDM system can accommodate multiple data rate signals by providing spectrally uniform high gain for high data rate channels, and low gain for lower rate channels. Improved signal quality can thus be achieved for both high speed and low speed signals in a single WDM system.

Abstract: In the WDM systems, the OSNR and the signal loss among the optical signals are substantially minimized at the receiving terminal to combat the SRS effects. An equal amount of the signal loss is expected for every span in the transmission path so that the optical amplifier gain tilt is not affected among a number of wavelength frequencies in the optical signal. This is accomplished by controlling the amplification process according to a feedback from the monitoring units for monitoring the optical signal.

Abstract: A power controlling network element for a communication system includes a detector for measuring radiation power present in components of radiation; element parts, for example a channel control unit (CCU), transponders and other modules, for at least one of: (i) transmitting to the detector at least some components of input radiation received at the elements parts from the system; and (ii) generating one or more components of radiation and emitting the one or more components to the detector; and a field programmable gate array (FPGA) for receiving data from the detector indicative of radiation power in the components of radiation received at the detector, and for controlling radiation power emitted from or transmitted through the aforementioned element parts so that the components of radiation received at the detector are regulated in power to within predetermined power limits.

Abstract: A device (D) is dedicated to controlling the power of optical signals in a transparent switching node of an optical communication network that switches bands of wavelengths. The device includes, firstly, a controller (12) for comparing input optical power measurements to a selected first threshold and generating instructions representative of the comparison result, secondly, a measuring device (10A) for delivering measurements representative of the input optical power of the optical signals at one output at least of the switch (4), and thirdly, a processor between the switch (4) and the multiplexer (6) of the node and which control the optical power of the signals coming from the switch (4) as a function of the instructions they receive, so that the optical power of the signals at the input of the multiplexer (6) is maintained substantially constant.

Abstract: A technique for maintaining a required value of power per optical communication channel in a chain of optical nodes (112, 114, 118, 116) connected by optical fiber spans (111, 119, 121), wherein at least some of the nodes include optical amplifiers (112, 114, 116) with controllable gains, the technique comprises performing automatic gain control at the optical amplifiers so that, in the frame of power gain of each particular optical amplifier (114, 116), to compensate a preceding span loss. The span loss is calculated as power loss on an optical fiber span (111,121) incoming the particular amplifier.