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: A method of distinguishing whether a detected change in reflected power in an optical time domain reflectometer (OTDR) measurement carried out in a fiber optic transmission system (16) using an OTDR is caused by a an event causing actual attenuation or a change in a mode field diameter, comprising the steps of emitting a succession of first sampling light pulses of a first wavelength into the fiber optic transmission system (16) while a pumping signal with a second wavelength is emitted into the fiber optic transmission system (16), and measuring a first OTDR trace (34?) resulting from the reflection of the first sampling light pulses in the fiber optic transmission system (16), such that the first sampling light pulses and their reflections interact with the pumping signal via stimulated Raman scattering.

Abstract: An optical network is suggested, comprising a first set of optical fibers, a multimode multiplexer, a multimode amplifier, a multimode demultiplexer, and a second set of optical fibers, wherein the first set of optical fibers is connected via the multimode multiplexer to the multimode amplifier and wherein the multimode amplifier is connected via the multimode demultiplexer to the second set of optical fibers. Accordingly, an optical network element is provided.

Abstract: The proposed invention is in the area of managing resources in optical transport networks, for example in the area of in-operation media channel format and spectrum management. For this purpose, the type of Media Channel Format is determined for each of a plurality of candidate paths, wherein each candidate path connects a pair of nodes in an optical transport network. Then, the expected weight describing traffic volume of each of the candidate paths is determined, and a spectrum share is assigned to each link of each of the candidate paths based on the determined Media Channel Formats and determined weights. In this way, spectrum shares assigned to different links and candidate paths can be used for efficiently assigning a band spectrum to each of the Media Channel Formats of the candidate paths.

Abstract: The present invention relates to adding and dropping signals in a node of an optical network, wherein the node includes a reconfigurable optical add/drop multiplexer (ROADM). The reconfigurable optical add/drop multiplexer (ROADM) comprises output ports and at least one add port connectable to at least one line interface of the network and adapted to receive a modulated optical signal from the line interface. Selection units are connected to one of said add ports and adapted to forward the respective signals to a selected output terminal. A plurality of broadcast units is adapted to broadcast signals forwarded by the selection. Then a multiplexing and selecting device or apparatus selects and multiplexes the optical signals broadcast via broadcast unit output terminals into a plurality of wavelength-division multiplexing (WDM) optical signals and forwards the same to output ports of the reconfigurable optical add-drop multiplexer (ROADM).

Abstract: A method and device is provided for reducing optical transmission impairments, particularly nonlinear effects, of at least one link Said method comprising the following steps: extracting a phase information (??) from an optical signal (120) received via that at least one link, determining a nonlinear coefficient (?), associated with the at least one link, based on the phase information (??), applying a control mechanism (202) using the nonlinear coefficient (?). Furthermore, a communication system is suggested comprising said device.

Abstract: A method and a device for service provisioning in a communication network are provided, wherein a resource is utilized in the communication network, which resource is not yet available for productive use by the network. Also, an according communication system comprising at least one such device is suggested.

Abstract: The present invention relates to signal processing in an optical receiver, in particular to equalization performed in coherent optical receivers. A multiple-input multiple-output (MIMO) equalizer receives and equalizes a plurality of real value signals, for example four sampled electrical baseband tributaries (HI, HQ, VI, VQ). The outputs of the multiple-input multiple-output (MIMO) equalizer provide equalized real or imaginary components of complex signals. The complex signals including the real and imaginary components are then each and individually equalized to remove chromatic dispersion.

Abstract: At least one data-stream is re-routed and a network element is provided for re-routing at least one data-stream. A first part and a second part of a data-stream received at a first node and are transmitted to a second node via two different network paths, respectively. The first is transmitted from the first node to the second node via a first network path. A second network path is determined, and the difference between latencies of the first and second network paths is also determined. If the latency of the first network path is larger than the latency of the second network path, the at least one data-stream at the first node is re-routed from the first network path to the second network path provided that the time gap between data packets received by the first node exceeds said difference between latencies.

Abstract: A method for data processing of an optical network unit is provided, the method comprising the steps of receiving a configuration information at the optical network unit, adjusting a light signal to a wavelength or wavelength range indicated by the configuration information, demodulating an incoming optical signal by means of the light signal, mixing the demodulated incoming optical signal with a signal generated by an oscillator and generating a modulated optical upstream signal modulating the light signal by means of a software radio, so that the resulting optical upstream frequency can be shifted with respect to the frequency of the local oscillator by a programmable amount. Furthermore, an according device and a communication system are suggested comprising at least one such device.

Abstract: Disclosed herein is a decoder 10 for decoding a family of L rate compatible parity check codes, said family of parity check codes comprising a first code that can be represented by a bipartite graph having variable nodes, check nodes, and edges, and L?1 codes of increasingly lower code rate, among which the i-th code can be represented by a bipartite graph corresponding to the bipartite graph representing the (i?1)-th code, to which an equal number of n1 variable nodes and check nodes are added, wherein the added check nodes are connected via edges with selected ones of the variable nodes included in said i-th code, while the added variable nodes are connected via edges with selected added check nodes only. The decoder comprising L check node processing units 14, among which the i-th check node processing unit processes only the check nodes added in the i-th code over the (i?1)-th code, wherein said L check node processing units 14 are configured to operate in parallel.

Abstract: A method for determining the position of an irregularity in an optical transmission fiber using an optical time domain reflectometer, the method comprising the steps of emitting a succession of sampling light pulses into the optical transmission fiber, detecting reflected light pulses resulting from the reflection of the sampling light pulses at the irregularity in the optical transmission fiber and generating corresponding time-dependent detection signals, wherein different delays are associated with detection signals corresponding to different sampling light pulses, obtaining a combined signal from the detection signals, and analyzing the combined signal for determining the position of the irregularity in the optical transmission fiber with respect to the optical time domain reflectometer, wherein the combined signal corresponds to a super-position of the detection signals.

Abstract: A phase modulation device is provided that comprises a retardation device and a control device. The retardation device is characterized by first and second polarization eigenstates SOPf and SOPs. Light polarized according to the second polarization eigenstate SOPs acquires, upon passing through said retardation device, a delay with regard to light polarized according to the first polarization eigenstate SOPf, which delay corresponds to ?/2±30%, preferably ?/2±20% and most preferably ?/2±10%. The retardation device is arranged to receive input light having a polarization state SOPf; that defines an angle with respect to one of the first and second polarization eigenstates SOPf, SOPs within a predetermined angle range and to emit output light. The control device is configured to control at least one of a change of the angle between the polarization state SOPi; of the input light and the respective polarization eigenstate SOPf, SOPs by less than 0.1*?, preferably less than 0.05*? and most preferably less than 0.

Abstract: Disclosed herein is a dual parallel Mach-Zehnder-modulator (DPMZM) device comprising a DPMZM 10 having first and second inner MZMs arranged parallel to each other. The first inner MZM generates an in-phase component EI of an optical signal in response to a first driving voltage VI, and the second inner MZM generates a quadrature component EQ of said optical signal in response to a second driving voltage VQ. Further disclosed is a calculation unit 52 configured for receiving an in-phase component yI and a quadrature component yQ_ of a desired base-band signal, and for calculating pre-distorted first and second driving voltages VI, VQ. The calculation of the pre-distorted first and second driving voltages VI, VQ is based on a model of said DPMZM 10 accounting for I-Q cross-talk, and using an algorithm that determines said first and second driving voltages VI, VQ each as a function of both of said in-phase and quadrature components yI, yQ of said base-band signal.

Abstract: Disclosed is a method for decoding an optical data signal. Said optical data signal is phase and amplitude modulated according to a constellation diagram with at least eight constellation points representing non-binary symbols. Said decoding method comprises the following steps: —carrying out a carrier phase recovery of a received signal ignoring the possible occurrence of phase slips, —decoding said signal after phase recovery, wherein in said decoding, possible cycle slips occurring during phase recovery are modelled as virtual input to an equivalent encoder assumed by the decoding scheme. Further disclosed are a related encoding method as well as a receiver and a transmitter.

Abstract: An encoder encodes digital data, said encoder includes one or more component encoders, one or more interconnections between component encoders, one or more inputs and one or more outputs. The encoder is configured to carry out the following steps: combining internal input bits received via an interconnection and external input bits received via a corresponding input, to assemble a local information word, encoding the local information word such as to generate a local code word, outputting a reduced local code word and handling the same reduced local code word over to the interconnect for forwarding the same reduced local code word to another component encoder or to itself, wherein the encoder is configured to forward on each interconnect the bits of the reduced local code in parallel but with delays that are mutually different for at least a subset of the reduced local code word bits.

Abstract: Enclosed herewith is a method for protecting a link in an optical network configured for transmitting digital data employing a predetermined modulation format which comprises a number of symbols in a constellation diagram. A binary address is associated with each symbol. The modulation format allows for a constellation distortion, according to which the relative positions of constellation points in the constellation diagram are varied in a predetermined way by a predetermined degree.

Abstract: Disclosed is a method of Controlling a gain of an optical amplifier comprising a gain medium and at least one pumping device. The method comprises the following steps: determining or predicting a change of input signal power to the amplifier, changing the pump power from an initial pump power level to a new pump power level at a first time instant, the initial pump power level being the pump power level applied to the amplifier prior to the change in input signal power, setting the pump power to a second pump power level at a second time instant, wherein the pump power level is varied in an oscillatory manner for at least one period of time starting at a third time instant and ending at a fourth time instant, wherein said third time instant is identical with or later than said first time instant and said fourth time instant is identical with or earlier than said second time instant.

Abstract: A Raman pumping arrangement for amplifying a data optical signal (40) has a Raman pump (12) for generating a Raman pump signal (44;45), an optical supervisory channel receiver (14) for receiving an optical supervisory channel signal (42) an amplification fiber (15) arranged such that the data optical signal (40), the optical supervisory channel signal (42), and the Raman pump signal (44;45) are transmitted therethrough; and a control unit (13) configured for controlling the operation of the Raman pump (12); wherein the control unit (13) is configured for setting the Raman pump (12) in an operation mode or a start-up mode; wherein in the operation mode, the Raman pump (12) provides an operation pumping power (120), and wherein in the start-up mode, the Raman pump (12) provides a start-up pumping power (122).

Abstract: In a method and system for decoding a differential M-ary phase or quadrature amplitude modulated signal, the incoming signal is decoded according to a plurality of different decoding rules, wherein said plurality of decoding rules correspond to different values of a resulting frequency difference or mismatch between a signal frequency and a local oscillator reference frequency. The invention allows to increase a tolerance window for the maximal allowable frequency offset, and thus helps to speed up an initial locking process or to allow for equipment which has a lower tuning granularity.