摘要:
A method of transmitting a data signal in an optical communications system. The method includes processing the data signal to generate an analog drive signal, wherein the processing comprises applying a first non-linear operation such that frequency components of the drive signal lay in at least two separated spectral bands. An optical carrier light is modulated using the analog drive signal.
摘要:
A transmitter comprises a complex mixer to generate a single I analog drive signal and a single Q analog drive signal, and a single multi-dimensional optical modulator configured to modulate an optical carrier light using the single I analog drive signal and the single Q analog drive signal to produce a modulated optical signal for transmission. Alternatively, a transmitter comprises a complex mixer to generate two I analog drive signals and two Q analog drive signals, and a single multi-dimensional multiple-electrode optical modulator configured to modulate an optical carrier light using the analog drive signals to produce a modulated optical signal for transmission. In both transmitters, the optical carrier light is produced by a single laser, and frequency components of the first data signal are located in a different portion of a spectrum of the modulated optical signal than frequency components of the second data signal.
摘要:
Forward Error Correction technique: parity vectors are computed such that each parity vector spans multiple FEC frames; in a given FEC frame, a first set of syndrome bits are due to the parity vectors, and a second set of syndrome bits satisfy FEC equations that involve bits of the given FEC frame including the first set of syndrome bits; and the parity vectors are staggered with respect to any sequence in which the FEC frames are processed. Values of decoded bits of a first frame are deduced from known bits of a first parity vector having an effective length of one frame. For parity vectors having an effective length greater than one frame, a Log Likelihood Ratio of each unknown bit associated with the first frame is updated based on known and unknown bits of each parity vector. First frame is decoded using deduced bit values and updated LLR values.
摘要:
In a Forward Error Correction (FEC) technique, parity vectors are computed such that: each parity vector spans a set of frames; a subset of bits of each frame is associated with parity bits in each parity vector; and a location of parity bits associated with one frame in one parity vector is different from that of parity bits associated with the frame in another parity vector. Values of decoded bits of a first frame are deduced from known parity bits of a first parity vector having an effective length of one frame. For parity vectors having, an effective length greater than one frame, a Log Likelihood Ratio of each unknown parity bit associated with the first frame is updated based on known and unknown parity bits of each parity vector. The first frame is decoded using the deduced bit values and the updated LLR values.
摘要:
A transmitter in an optical communications system includes a digital signal processor for processing a data signal to generate a sample stream encoding successive symbols in accordance with a constrained phase modulation scheme having a constellation of at least two symbols and a modulation phase constrained to a phase range spanning less than 4π. A digital-to-analog converter converts the sample stream into a corresponding analog drive signal. A finite range phase modulator modulates a phase of a continuous wavelength channel light in accordance with the analog drive signal, to generate a modulated channel light for transmission through the optical communications system. A receiver in the optical communications system includes an optical stage for detecting phase and amplitude of the modulated channel light and for generating a corresponding sample stream, and a digital signal processor for processing the sample stream to estimate each successive symbol of the modulated channel light.
摘要:
A method performed at an electronic device comprises receiving information bits, a first nub, and a second nub, each nub comprising redundant values; calculating first calculated determiners from first subsets of the information bits along a first dimension; calculating first corrected determiners by applying first FEC decoding to a combination of the first calculated determiners and the first nub; correcting at least one error in the information bits using a difference between the first corrected determiners and the first calculated determiners; calculating second calculated determiners from second subsets of the information bits along a second dimension that differs from the first dimension; calculating second corrected determiners by applying second FEC decoding to a combination of the second calculated determiners and the second nub; and correcting at least one additional error in the information bits using a difference between the second corrected determiners and the second calculated determiners.
摘要:
A receiver apparatus comprises circuitry configured for storing a first sequence of values. At the receiver apparatus, a communications signal is received which conveys a second sequence of values, the second sequence of values being related to the first sequence of values. According to some examples, the second sequence of values is identical to the first sequence of values. At the receiver apparatus, P results are calculated from a cross-correlation of the first sequence of values with at least a portion of a representation of the communications signal, where P is a positive integer. According to some examples, P≥2. An estimate of a phase offset of a continuous clock is calculated as a function of the P results. According to some examples, the function is a non-linear function. The estimate of the clock phase offset may be used to achieve clock recovery at the receiver apparatus.
摘要:
A receiver applies first processing to a digital representation of a received signal to generate a first processed signal having first additive noise and first linear inter-symbol interference (ISI), the first processing comprising a substantially linear operation designed to substantially minimize a sum of variances of the first additive noise and the first linear ISI. The receiver applies second processing to the first processed signal to generate a second processed signal having second additive noise and second linear ISI, the second processing comprising a substantially nonlinear operation designed (i) to make a variance of the second additive noise substantially lower than the variance of the first additive noise, and (ii) to make a sum of the variance of the second additive noise and a variance of the second linear ISI substantially lower than the sum of the variances of the first additive noise and first linear ISI.
摘要:
A method of transmitting a data signal using an optical transmitter of an optical communications system. The optical transmitter is configured to modulate an optical carrier in successive signalling intervals to generate an optical signal. A modulation scheme is provided which comprises a multi-dimensional symbol constellation. The modulation scheme is designed such that an average degree of polarization of a modulated optical signal output from the optical transmitter has a first value when averaged across a first signaling interval, and has a second value when averaged across more than one and fewer than 100 signaling intervals. The second value is less than 10 percent of the first value. During run-time, an encoder of the optical transmitter encoding a data signal to be transmitted as symbols of the constellation, and a modulator of the optical transmitter modulating available dimensions of the optical carrier in accordance with the symbols.
摘要:
A method of recovering a value of a symbol received through an optical communications system. A multi-bit estimate of the symbol is subdivided into a first part and a second part, each part including at least one respective bit of the estimate. A most likely value of the first part is detected. The most likely value of the first part is processed using a Forward Error Correction (FEC) decoder to generate a corrected first part value, which is used to detect a most likely value of the second part. The most likely value of the second part is then processed by the FEC decoder to generate a corrected second part, which is combined with the corrected first part to recover the value of the symbol.