摘要:
Consistent with the present disclosure, data, in digital form, is received by a transmit node of an optical communication system, is processed and then output to drive a modulator. The modulator, in turn, modulates light at one of a plurality of wavelengths in accordance with the received data, forming a plurality of corresponding carriers. The plurality of wavelengths used for the plurality of carriers are spectrally spaced apart by a common, periodic fixed spacing. The plurality of carriers are optically combined with a fixed spacing combiner to form a superchannel. A plurality of superchannels are generated and then multiplexed together onto an optical communication path and transmitted to a receive node. Each superchannel includes a plurality of carriers, each spectrally separated by the same fixed spacing. The plurality of superchannels are spectrally separated by an amount corresponding to the fixed spacing of the plurality of carriers. At the receive node, the superchannels are optically demultiplexed, and the plurality of carriers of a respective superchannel are then supplied to a photodetector circuit, which receives additional light at one of the optical signal carrier wavelengths from a local oscillator laser. The resultant signals are then processed electronically to separate the individual carriers and output data corresponding to the input data.
摘要:
Consistent with the present disclosure, data, in digital form, is received by a transmit node of an optical communication system, and is then provided to a modulator that, in turn, modulates light, received from an optical source at one of a plurality of periodically and preferably minimally spaced wavelengths. The plurality of periodically spaced wavelengths or carriers are grouped together with minimal carrier spacing, to form a superchannel. The carrier spacing between adjacent carriers is determined by detecting a beat frequency of a combined optical signal that includes the outputs of two adjacent optical sources. The beat frequency corresponds to a frequency difference between the outputs of the adjacent carriers. This frequency difference should correspond to a desired carrier spacing between each of the plurality of carriers. A frequency error between the beat frequency and the desired carrier spacing is then measured by down-converting the beat frequency with respect to a target reference frequency corresponding to the desired carrier frequency spacing. Based on the determined frequency error, the optical sources are controlled to adjust in frequency to minimize or reduce the frequency error to zero. For every pair of adjacent carriers, the corresponding outputs of the optical sources are compared in the above manner to determine a plurality of frequency errors. Each optical source can thus be tuned in order to realize a precise carrier spacing between each of the adjacent carriers.
摘要:
Consistent with the present disclosure, data, in digital form, is received by a transmit node of an optical communication system, is processed and then output to drive a modulator. The modulator, in turn, modulates light at one of a plurality of wavelengths in accordance with the received data, forming a plurality of corresponding carriers. The plurality of wavelengths used for the plurality of carriers are spectrally spaced apart by a common, periodic fixed spacing. The plurality of carriers are optically combined with a fixed spacing combiner to form a superchannel. A plurality of superchannels are generated and then multiplexed together onto an optical communication path and transmitted to a receive node. Each superchannel includes a plurality of carriers, each spectrally separated by the same fixed spacing. The plurality of superchannels are spectrally separated by an amount corresponding to the fixed spacing of the plurality of carriers. At the receive node, the superchannels are optically demultiplexed, and the plurality of carriers of a respective superchannel are then supplied to a photodetector circuit, which receives additional light at one of the optical signal carrier wavelengths from a local oscillator laser. The resultant signals are then processed electronically to separate the individual carriers and output data corresponding to the input data.
摘要:
Consistent with the present disclosure, data, in digital form, is received by a transmit node of an optical communication system, and is then provided to a modulator that, in turn, modulates light, received from an optical source at one of a plurality of periodically and preferably minimally spaced wavelengths. The plurality of periodically spaced wavelengths or carriers are grouped together with minimal carrier spacing, to form a superchannel. The carrier spacing between adjacent carriers is determined by detecting a beat frequency of a combined optical signal that includes the outputs of two adjacent optical sources. The beat frequency corresponds to a frequency difference between the outputs of the adjacent carriers. This frequency difference should correspond to a desired carrier spacing between each of the plurality of carriers. A frequency error between the beat frequency and the desired carrier spacing is then measured by down-converting the beat frequency with respect to a target reference frequency corresponding to the desired carrier frequency spacing. Based on the determined frequency error, the optical sources are controlled to adjust in frequency to minimize or reduce the frequency error to zero. For every pair of adjacent carriers, the corresponding outputs of the optical sources are compared in the above manner to determine a plurality of frequency errors. Each optical source can thus be tuned in order to realize a precise carrier spacing between each of the adjacent carriers.
摘要:
An optical transmitter may include an optical source to provide a first optical signal having a varying frequency; an optical circuit to receive a portion of the first optical signal and provide a second optical signal corresponding to a change in frequency of the first optical signal; a photodetector to receive the first optical signal and provide an electrical signal that is indicative of the change in frequency of the first optical signal; an integrator to receive the electrical signal and provide an inverted electrical signal; and a controller to process the inverted electrical signal and provide a current, associated with the inverted electrical signal, to the optical source. The optical source may reduce the phase noise associated with the first optical signal based on the current.
摘要:
Consistent with the present disclosure, data, in digital form, is received by a transmit nodes of an optical communication, and converted to analog signal by a digital-to-analog converter (DAC) to drive a modulator. The modulator, in turn, modulates light at one of a plurality of wavelengths in accordance with the received data. The modulated light is then transmitted over an optical communication path to a receive node. At the receive node, the modulated optical signal, as well as other modulated optical signals are supplied to a photodetector circuit, which receives additional light at one of the optical signal wavelengths from a local oscillator laser. An analog-to-digital converter (ADC) is provided in the receive node to convert the electrical signals output from the photodetector into digital form. The output from the ADC is then filtered in the electrical domain, such that optical demultiplexing of individual channels is unnecessary.
摘要:
Consistent with the present disclosure, data, in digital form, is received by a transmit node of an optical communication, and converted to analog signal by a digital-to-analog converter (DAC) to drive a modulator. The modulator, in turn, modulates light at one of a plurality of wavelengths in accordance with the received data forming a plurality of corresponding carriers. The plurality of carriers are then optically combined with a fixed spacing combiner to form a superchannel of a fixed capacity. Accordingly, the number of carriers are selected according to a modulation format and symbol rate to realize the fixed capacity, for example. The superchannel is then transmitted over an optical communication path to a receive node. At the receive node, the superchannel is optically demultiplexed from a plurality of other superchannels. The plurality of carriers are then supplied to a photodetector circuit, which receives additional light at one of the optical signal carrier wavelengths from a local oscillator laser. An analog-to-digital converter (ADC) is provided in the receive node to convert the electrical signals output from the photodetector into digital form. The output from the ADC is then filtered in the electrical domain, such that optical demultiplexing of the carriers is unnecessary.
摘要:
Consistent with the present disclosure, a coherent detector is provided that includes an optical hybrid that supplies optical signals including local oscillator light to a balanced detector. The amount of imbalance or “balance error” in the balanced detector is identified by comparing an output of the balanced detector and an output of a photodiode that receives a portion of an input optical signal provided to the optical hybrid. Based on the balance error, electrical signals generated by the balanced detector or the power of optical signals passing through (or output from) the optical hybrid circuit can be adjusted so that the balance error is minimized or reduced to zero. As a result, imbalance associated with the balanced detector is corrected so that unwanted currents and/or related electrical signals are cancelled out or substantially cancelled out. Such unwanted currents and/or related electrical signals are generated in response to noise in the local oscillator light as well as intensity noise associated with non-selected optical signals in a superchannel.
摘要:
In a QAM microwave radio communications system an IF (intermediate frequency) input signal is amplified and predistorted, and the amplified IF signal is mixed with a local oscillator signal to produce an RF (radio frequency) signal which is amplified in a power amplifier for transmission, the predistortion compensating for non-linearity of the power amplifier. Adaptive phase control of the predistorter is provided by mixing the local oscillator signal with part of the RF signal to produce an IF output signal representative of the output of the power amplifier, detecting phase differences between the IF input and IF output signals to produce a phase difference signal, selectively inverting the phase difference signal in dependence upon whether or not an IF signal amplitude exceeds a comparison level, and integrating the selectively inverted phase difference signal to produce a phase control signal for the predistorter.
摘要:
The present invention provides a method of detecting the clock rate and recovering the carrier in a TDMA (time division multiple access) signal. The quadrature baseband components are stored for a predetermined amount of time as sampled data and the clock phase error of the baseband samples are estimated. The clock phase of the baseband samples are corrected from the estimated clock phase error by using interpolation over the sampled quadrature components. The carrier phase error of the stored baseband time corrected quadrature samples are then estimated and the carrier phase is corrected according to the estimated phase error. The corrected clock and carrier signals are then forwarded to decision circuit means for providing demodulated data.