Infinera Corporation

Ciena Corporation

Queen's University at Kingston

David J Krause

Han Henry Sun

John Duncan McNicol

Kim Bryon Roberts

Kuang-Tsan Wu

Charles Laperle

Yuejian Wu

John C Cartledge

Radhakrishnan L Nagarajan

Fred A Kish, Jr

Masaki Kato

Mehrdad Ziari

Jeffrey Thomas Rahn

Vikrant Lal

Pierre Mertz

Sandy Thomson

Mohsen Nader Tehrani

Damien Lambert

Methods, systems, and apparatus, including computer programs encoded on computer storage media, for clock recovery in subcarrier based coherent optical systems. In one aspect, an apparatus includes a plurality of phase detectors configured to generate a plurality of phase detection outputs by detecting a plurality of digital signals associated with a plurality of frequency bands, each of the plurality of phase detection outputs being associated with a respective one of the plurality of frequency bands, alignment circuitry coupled to the plurality of phase detectors and configured to align phases of the plurality of phase detection outputs to be substantially same, and averaging circuitry coupled to the alignment circuitry and configured to generate a particular output based on the plurality of phase detection outputs with the aligned phases. The plurality of digital signals is adjusted based on the particular output.

Clock recovery for subcarrier based coherent optical systems

A high speed signal generator comprises a digital signal processing (DSP) block configured to process an input digital signal to generate in parallel a first digital sub-band signal having frequency components within a first spectral range and a second digital sub-band signal having frequency components within the first spectral range. A first Digital-to-Analog Converter (DAC) is configured to process the first digital sub-band signal to generate a first analog sub-band signal and a second DAC is configured to process the second digital sub-band signal to generate a second analog sub-band signal. A combiner is to combine the first analog sub-band signal and the second analog sub-band signal to generate an output analog signal having frequency components covering a substantially continuous spectral range from a lower frequency fto a higher frequency f. The substantially continuous spectral range is substantially wider than a width of the first spectral range, and the lower frequency fis less than or equal to one-third of the higher frequency f.

High speed signal generator

An optical system includes a transmitter module and/or a receiver module. The transmitter module is configured to receive input data, map the input data to a set of subcarriers associated with an optical communication channel, independently apply spectral shaping to each of the subcarriers, generate input values based on the spectral shaping of each of the subcarriers, generate voltage signals based on the input values, modulate light based on the voltage signals to generate an output optical signal that includes the subcarriers, and output the output optical signal. The receiver module is configured to receive the output optical signal, convert the output optical signal to a set of voltage signals, generate digital samples based on the set of voltage signals, independently process the digital samples for each of the subcarriers, map the processed digital samples to produce output data, and output the output data.

Channel carrying multiple digital subcarriers

A high-speed signal generator. A digital signal processing (DSP) block generates a set of N (where N is an integer and N&#x2267;2) parallel digital sub-band signals, each digital sub-band signal having frequency components within a spectral range between 0 Hz and &#xb1;Fs/2. A respective Digital-to-Analog Converter (DAC) processes each digital sub-band signal to generate a corresponding analog sub-band signal, each DAC having a sample rate of Fs. A combiner combines the analog sub-band signals to generate an output analog signal having frequency components within a spectral range between 0 Hz and &#xb1;NFs/2.

A system may include an optical transmitter and an optical receiver. The optical transmitter may generate optical signals associated with sub-carriers, and may provide the optical signals via an optical link. The optical receiver may receive the optical signals via the optical link, and may generate samples based on the optical signals. The samples may be associated with the sub-carriers. The optical receiver may combine the samples to form a time domain sample vector having a particular size, and may generate a frequency domain sample vector, having the particular size, based on the time domain sample vector. The optical receiver may demultiplex the frequency domain sample vector to generate domain sample vectors corresponding to the sub-carriers. The optical receiver may process the frequency domain sample vectors to generate equalized frequency domain sample vectors, and may output the equalized frequency domain sample vectors.

Configurable frequency domain equalizer for dispersion compensation of multiple sub-carriers

A device may insert a set of tones into a transmitter signal at a set of frequency offsets from a set of transmitter channels associated with a set of transmitter channel wavelengths. The set of transmitter channels may include a first channel being associated with a first quantity of bandwidth and a second channel associated with a second quantity of bandwidth. The first quantity of bandwidth may be different from the second quantity of bandwidth. The device may repeatedly adjust the transmitter signal to align the set of transmitter channel wavelengths based on a set of observed responses to the set of tones, generated based on the transmitter signal passing through an optical filter, failing to match a set of expected responses.

Arbitrary grid wavelocking using digitally generated out-of-band tones

An optical system may include optical transmitters to provide respective optical signals. Each of the respective optical signals may provide one or more carriers in an optical channel. The optical channel may include multiple carriers associated with the respective optical signals. First and second carriers, of the multiple carriers, may have a particular carrier space width. The particular carrier space width may include a frequency error associated with one or more optical signals of the respective optical signals. The optical system may include a control system to determine the frequency error and cause one or more of the optical transmitters to adjust the particular carrier space width based on the adjusted frequency error.

Adjusting carrier spacing in a channel

An optical modulator includes a splitter, phase modulators, amplitude modulators, intensity modulators, and a combiner. The splitter is configured to receive light, and split the light into portions of the light. Each of the phase modulators is configured to receive a corresponding one of the portions of the light, and modulate a phase of the portion of the light to provide a phase-modulated signal. Each of the amplitude modulators is configured to receive a corresponding one of the phase-modulated signals, and modulate an amplitude of the phase-modulated signal to provide an amplitude-modulated signal. Each of the intensity modulators is configured to receive a corresponding one of the amplitude-modulated signals, and modulate an intensity of the amplitude-modulated signals to provide an intensity-modulated signal. The combiner is configured to receive the intensity-modulated signals, combine the intensity-modulated signals into a combined signal, and output the combined signal.

Intensity-based modulator

A high-speed signal generator. A digital signal processing (DSP) block generates a set of N (where N is an integer and N&#x2267;2) parallel digital sub-band signals, each digital sub-band signal having frequency components within a spectral range between 0 Hz and &#xb1;Fs/2, where Fs is a sample rate of the digital sub-band signals. A respective Digital-to-Analog Converter (DAC) processes each digital sub-band signal to generate a corresponding analog sub-band signal, each DAC having a sample rate of Fs/2. A combiner combines the analog sub-band signals to generate an output analog signal having frequency components within a spectral range between 0 Hz and &#xb1;NFs/2.

A transmitter module includes a processor configured to receive input data, and determine input values corresponding to the input data; a digital-to-analog converter configured to receive the input values from the processor, and generate first and second voltage signals based on the input values; a laser configured to output light; a Mach-Zehnder modulator configured to receive the light from the laser and the first and second voltage signals from the digital-to-analog converter, and modulate the light based on the first and second voltage signals to generate a modulated optical signal that includes distortion; and a filter configured to receive the modulated optical signal from the modulator, process the modulated optical signal to reduce or eliminate the distortion and produce an output optical signal, and output the output optical signal.

Dual-drive modulator

An optical system may have an optical transmitter including a digital signal processor to receive a signal channel, add data corresponding to a pilot tone, generate a digital signal associated with the signal channel and including the pilot tone, and output the digital signal. The optical system may further have a digital-to-analog converter to convert the digital signal to an analog signal, a laser to provide an optical signal, and a modulator to receive the optical signal and the analog signal, and modulate the optical signal based on the analog signal to form a modulated optical signal. The modulated optical signal may include the pilot tone. The optical system may also have an optical receiver to receive the modulated optical signal, process the modulated optical signal to determine a phase associated with the pilot tone, and apply the phase to the modulated optical signal to recover the signal channel.

Nonlinearity compensation using pilot tones

Systems and methods for determining the envelope of a modulated signal using high bandwidth and low bandwidth samples of a hybrid signal. The hybrid signal is obtained by mixing the modulated signal with its carrier signal. The systems and methods of the present disclosure may be suitable for equivalent-time or real-time oscilloscopes.

System and method for determining the envelope of a modulated signal

A system, method, and apparatus is disclosed for interpolation of an output of an analog to digital converter (ADC) to enable operation of the ADC at a sampling rate that is independent of the sampling rate for a DSP core so as to efficiently enable operation at higher date rates. According to one of the embodiments, an interpolation circuit is coupled between the ADC and DSP core and receives a first plurality of samples of data at the first data rate from the ADC and supplies a plurality of samples of second data at a second data rate to the DSP core; the second data rate being less than the first data rate. According to one of the embodiments, the interpolation circuit includes a memory and a FIR filter circuit having filter tap coefficient values selected to provide attenuation at high frequencies to reduce aliasing noise.

Method, system, and apparatus for interpolating an output of an analog-to-digital converter

A system, method, and apparatus is disclosed for enabling a constant modulus algorithm (CMA) to be reliably used for blind equalization training of an equalizer. According to one embodiment, received signals in a binary phase shift keying (BPSK) format are converted to a quadrature phase shift keying (QPSK) format, to which CMA processing can be reliably applied for equalization. According to another aspect of this embodiment, the equalized QPSK signals are rotated to convert the signals to an equalized BPSK format for output.

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Saskatoon, Canada

David J Krause