Telefonaktiebolaget Lm Ericsson (publ)

Ericsson Ab

Marco Secondini

Enrico Forestieri

Fabio Cavaliere

Luca Poti

Roberto Magri

Giulio Colavolpe

Gianluca Meloni

Antonio Malacarne

Domenico Marsella

Antonio D'Errico

Claudio Porzi

Tommaso Foggi

Francesco Fresi

Alessandra Bigongiari

Tommaso Catuogno

Giancarlo Prati

A photonic radio frequency, RF, signal generation apparatus has a source to output a coherent optical signal at a carrier frequency; an optical splitter to split the signal into a first and a second optical carrier signal; an RF signal generation apparatus generating an RF signal at an initial frequency; an optical modulation apparatus modulating the first and second signals at the initial frequency to generate optical harmonic signals around each signal; a first optical filter to select an nth order optical harmonic signal of a first sign, +n, of the optical harmonics around the first signal; a second optical filter to select the nth order optical harmonic signal of an opposite sign, −n, of the optical harmonics around the second signal; and a combiner to combine the selected +n and −n signals to generate an optical beat signal forming an output photonic RF signal.

Photonic RF signal generation apparatus, network units and method

A method () of encoding communications traffic bits onto an optical carrier signal in a pulse amplitude modulation, PAM, format. The method comprises: receiving () bits to be transmitted; receiving () an optical carrier signal comprising optical pulses having an amplitude and respective phases; performing () PAM of the optical pulses to encode at least one respective bit in one of a pre-set plurality of amplitudes of a said optical pulse; and performing () phase modulation of the optical pulses to encode at least one further respective bit in a phase difference between a said optical pulse and a consecutive optical pulse.

Encoding and decoding communications traffic in a pulse amplitude modulation format and optical apparatus for same

A method of transmitting communications traffic, the method comprising steps of receiving a sequence of communications traffic bits; and mapping the sequence of communications traffic bits onto a respective one of a plurality of transmission symbols for transmission during a symbol time. Each transmission symbol is identified by a respective first symbol identifier indicative of a respective one or more of a plurality, M, of wavelengths for a transmission signal and a respective second symbol identifier indicative of a respective one or more of a plurality, N, of optical fibers on which to transmit the transmission signal.

Method of transmitting communications traffic, transmitter and communications transmission system

A digital signal processing, DSP, unit () for use in a coherent optical receiver for an optical communications network. The DSP unit comprises an adaptive equalizer () and a processing block (). The equalizer () comprises input ports for receiving electrical signals, each corresponding to a different state of polarization of an optical signal received by the coherent optical receiver, and output ports, each connected to a processing branch (). A processing branch comprises a symbol sequence estimator, SSE, () and a carrier phase estimator, CPE, () comprising an input for receiving signal taped from an output of the processing branch. An output of the CPE is connected to a phase adjuster () interconnecting the respective output port of the equalizer and the SSE. The processing block () is connected to an output of the CPE, an output of the processing branch and at least one of the output of the phase adjuster and the outputs of the equalizer.

Digital signal processing of an optical communications signal in a coherent optical receiver

A method () of non-linear propagation impairment equalization, the method comprising the steps of: a. receiving () communications traffic carried by an optical communications signal transmitted over an optical communications link; b. generating () a time dependent filter representation of a nonlinear time-variant impulse response of the inverse of the optical communications link; and c. applying () the time dependent filter representation to the received communications traffic to form non-linear propagation impairment equalized communications traffic. An optical communications link nonlinear propagation impairment equalizer and optical communications signal receiver apparatus are also provided.

Non-linear propagation impairment equalization

A muxponder comprising: modulation format conversion apparatus comprising:

Muxponder and method of converting a plurality of tributary optical communications signals having a first bit rate into an optical line signal having a second, higher bit rate

A 2-QAM (e.g. 16-QAM) optical modulator comprising cascaded I-Q modulators. The first I-Q modulator applies 2(e.g. 4) QAM to an optical signal, having a constellation diagram with the 2(e.g., 4) constellation points located in quadrant I. The second I-Q modulator subsequently applies a quaternary phase-shift keying (QPSK) modulation scheme to the optical signal, thereby rotating the constellation points of the 2-QAM modulation scheme to quadrants II, III and IV, to produce a 2-QAM modulation constellation diagram. The rotation causes the 2-QAM modulator to inherently apply four quadrant differential encoding to the optical signal. A method of 2-QAM optical modulation is also provided and optical signal transmission apparatus comprising the 2-QAM optical modulator.

Optical signal modulation

A method of detecting a signal in an optical receiver is described. The method includes converting a received optical signal to a digital electrical signal comprising a plurality of samples, applying a predetermined phase rotation to said samples to obtain amplitude and phase components of phase range adjusted sample values, and performing a first detection process based on the amplitude and phase components of the phase range adjusted sample values.

Receiver for optical transmission system

An equalizer () processes, in the electrical domain, a signal obtained from a path of an optical transmission system. The equalizer comprises N cascaded stages (where N&#x2267;1). At least one of the stages comprises a cascade of a linear equalization element () and a non-linear equalization element (). The equalizer () is able to compensate for both linear impairments, such as dispersion, and non-linear impairments. The cascaded linear and non-linear elements can simulate the effect of signal propagation through a fiber which has the opposite propagation parameters (e.g. attenuation, dispersion, non-linearity) to those of the propagation path experienced by a signal in the transmission system. The non-linear equalization element () can be a non-linear phase rotator which rotates phase of an input signal proportional to the squared modulus of the input signal amplitude. The linear equalization element () can comprise a digital filter, such as an Infinite Impulse Response (HR) filter or a Finite Impulse Response (FIR) filter.

Equalizer for an optical transmission system

A method () of compensating phase noise in a coherent optical communications network. The method comprises: receiving a traffic sample (); receiving an optical carrier and determining a phase noise estimate for the optical carrier (); and removing the phase noise estimate from the traffic sample to form a phase noise compensated traffic sample ().

Phase noise compensation in coherent optical communications systems

A polarization multiplex transmission system () comprises two optical signals (z, z) transmitted over the same optical fiber () at the same wavelength but with orthogonal polarizations. The system is characterized by receiving apparatus () which is operable to filter the two components with orthogonal polarization of the signal received in accordance with an appropriate transfer matrix which is dynamically controlled on the basis of the output signals in such a manner as to approximate the reverse transfer matrix of the fiber in the region of the spectrum occupied by the signal so as to compensate for Polarization Mode Dispersion (PMD) and polarization rotation introduced by the fiber and eliminating distortion and mutual interference effects for both the signals and thereby obtain a demultiplexed output corresponding to the two transmitted signals.

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Rome, Italy

Marco Secondini