10 results about "Subcarrier multiplexing" patented technology

The invention provides a low-complexity nonlinear compensation method and system for digital subcarrier multiplexing optical communication, and the method comprises the steps: calculating a nonlinear coefficient of a digital subcarrier multiplexing optical communication system, and carrying out the quantization processing of the nonlinear coefficient through employing a uniform quantization mode; by taking the cross-section length as a processing step length, converting the time domain signal of each subcarrier to a frequency domain for dispersion compensation, and then converting the compensated signal back to the time domain; calculating nonlinear phase noise in the subcarriers based on the time domain signal intensity of each subcarrier by taking the cross-section length as a processing step length, and performing phase rotation compensation; and calculating inter-subcarrier nonlinear phase noise and inter-polarization crosstalk based on the quantized nonlinear coefficient, subcarrier signal strength and inter-polarization crosstalk strength by taking the cross-section length as a processing step length, constructing a nonlinear compensation matrix and performing matrix compensation. According to the invention, the calculation complexity of an optical fiber nonlinear compensation algorithm is reduced, and efficient nonlinear compensation of a digital subcarrier multiplexing optical communication system is realized.

The invention discloses a digital subcarrier multiplexing signal frequency offset processing method and system based on a frequency spectrum protection interval, and relates to the field of optical fiber communication. The method comprises the steps that a digital subcarrier multiplexing signal is obtained through coherent receiving and subjected to smooth filtering, the digital subcarrier multiplexing signal comprises a plurality of subcarriers, and a guard interval with a preset frequency width is inserted between the highest-frequency subcarrier and an adjacent carrier of the highest-frequency subcarrier. Searching signal power spectrum minimum value points in a given frequency range by taking a preset guard interval center frequency as a center, and calculating the power sum of all frequency components in a guard interval frequency width range by taking the frequencies corresponding to the searched minimum value points as the center; and selecting the power and the frequency corresponding to the minimum value point as the estimated value of the center frequency of the guard interval, thereby completing the estimation and compensation of the frequency offset. The method is transparent to a modulation format and a spectrum roll-off factor, and has high tolerance to an optical filtering effect of a link.

This communication device serving as an aggregation station comprises: a signal processing unit that generates a main signal and a control signal; and a subcarrier multiplexing unit that arranges the main signal and the control signal in each of a first sideband and a second sideband with a carrier frequency as a reference, and generates an intensity-modulated optical signal including the control signal having opposite phases in the first sideband and the second sideband. This communication device serving as an extension station comprises: a photoelectric converter that converts, into an electrical signal, an intensity-modulated optical signal based on a main signal and a control signal arranged at the same frequency; a first filter that generates the main signal by passing, among the converted electrical signals, an electrical signal of a first frequency; a second filter that passes, among the converted electrical signals, an electrical signal of a second frequency; and a control signal generation unit that generates the control signal on the basis of the electrical signal of the first frequency and the electrical signal of the second frequency.

This invention discloses a coherent transmission method and PON system based on digital subcarrier multiplexing, relating to the field of optical access network technology. The method includes: in the downlink transmission direction, the OLT transmitter generates an Alamouti-coded signal of M digital subcarriers, performs digital-to-analog conversion and dual polarization modulation, and transmits it as a downlink signal to the ONU receiver; the ONU receiver performs heterodyne coherent detection, analog-to-digital conversion, and digital signal processing, with the downlink signal occupying a single-sideband spectrum of the ONU's light source; in the uplink transmission direction, the ONU transmitter generates data of M digital subcarriers, performs digital-to-analog conversion, and then performs single-sideband modulation based on the ONU's light source, transmitting it as an uplink signal to the OLT receiver, with the uplink signal occupying another single-sideband spectrum; the OLT receiver performs analog-to-digital conversion and digital signal processing after coherent reception. This application enables bidirectional high-speed transmission, and uses the same light source for both transmission and reception at the ONU, which increases the capacity of the PON system, simplifies the ONU's structure and algorithm, and reduces system costs.

The application discloses a kind of based on digital subcarrier multiplexing multi-passive optical network system and its dynamic bandwidth allocation method, the scheme is divided into multiple independent adjustable subcarrier channels by digital subcarrier multiplexing technology on electric domain, and the number of subcarriers is dynamically adjusted and distributed to each PON, so as to realize the differentiated bandwidth allocation between different PONs, satisfy the bandwidth demand between multi-PON changes with region and time.The steps of dynamic bandwidth allocation method are: step S1: predict bandwidth demand, calculate demand satisfaction rate and determine priority for each ONU (Optical Network Unit) in multi-PON;Step S2: count the bandwidth demand of different priority of each PON;Step S3: calculate and dynamically allocate a certain number of subcarriers for each PON;Step S4: dynamically allocate bandwidth to each ONU in PON according to priority;Step S5: activate / close neighbor subcarrier;Step S6: global subcarrier reconfiguration is carried out.

The invention discloses a low-crosstalk long-distance sensing integrated device and a very-low-frequency sensing method, and relates to the technical field of fusion of optical fiber sensing and optical fiber communication. The device comprises a laser, a coupler, a communication modulation device, a sensing modulation device, an optical fiber transmission and relay link, a communication receiving device, a sensing receiving device and a signal processing device. The communication modulation device adopts digital subcarrier multiplexing and reserves a guard interval in a frequency spectrum center, and residual carrier filtering is combined to reduce the inductance crosstalk; the sensing modulation device realizes high-extinction-ratio pulses through a cascade light modulator, and the signal-to-noise ratio is improved. The optical fiber link adopts a bidirectional amplification relay module to synchronously amplify forward and backward signals so as to realize ultra-long distance transmission. The signal processing device carries out high-density sampling and space-time dimension fusion on the sensing beat frequency signals, and very low frequency vibration information is effectively extracted. According to the invention, common-light-source, low-crosstalk, long-distance, very-low-frequency and high-sensitivity integrated transmission and detection of communication and sensing signals are realized.

The application provides a resource coordination optimization method and device for integrating sensing and communication in a MU-MIMO system, and relates to the technical field of wireless communication. The method comprises the following steps: establishing a communication-sensing performance coupling model, converting the maximization of communication rate and the minimization of radar beam matching error into a multi-objective optimization problem through the joint representation of subcarrier level beam direction and resource multiplexing relationship; constructing a sensing accuracy constraint system based on partial subcarrier multiplexing, screening multiplexing subcarriers through beam direction similarity measurement, and separating communication dedicated resources and communication sensing multiplexing resources; designing a hierarchical iterative optimization mechanism under a hybrid beamforming architecture, taking each iteration for solving the trade-off problem of communication rate and beam adaptation as a layer of a deep neural network, and optimizing the weight and step length through back propagation. The application guarantees the multi-user communication rate, optimizes the target sensing accuracy, and reduces the hardware implementation complexity of large-scale antenna systems.

An optical imager with subcarrier multiplexing uses a source transmit beam to simultaneously emit SFM transmit beams towards a target and receives SFM receive beams reflected off the target. The SFM receive beams are combined to provide a total receive beam, and the total receive beam is combined with a reference beam having the same frequency modulation as the source transmit beam to provide a receive signal that is configured for extraction of image data associated with the target.

This invention relates to a clock synchronization method and apparatus in a digital subcarrier multiplexing system. The method includes: interpolating a multiplexed signal sampling sequence comprising multiple subcarriers based on a fractional interval and a basic pointer; demultiplexing the multiplexed signal sampling sequence to obtain multiple subcarrier signal sampling sequences; performing dispersion compensation on each of the multiple subcarrier signal sampling sequences; selecting a target subcarrier signal sampling sequence from the dispersion-compensated multiple subcarrier signal sampling sequences for timing error detection to obtain timing error information; calculating the fractional interval and the basic pointer based on the timing error information; determining the conversion parameter of the fractional interval based on the symbol rate of each subcarrier signal sampling sequence, and converting the fractional interval according to the conversion parameter; and interpolating the multiplexed signal sampling sequence based on the basic pointer and the converted fractional interval. This completes one feedback loop, and after several feedback loops, the timing error of the multiplexed signal sampling sequence is eliminated.

This optical communication system comprises: a station-side device that has an optical transceiver of a subcarrier multiplexing scheme; a plurality of home-side devices that each have an optical transceiver of a subcarrier multiplexing scheme; and an optical distribution network that connects the station-side device and the plurality of home-side devices. The station-side device transmits a plurality of downlink subcarriers to the plurality of home-side devices via a time division scheme, receives an uplink subcarrier from at least one of the plurality of home-side devices via the subcarrier multiplexing scheme, and demodulates the uplink subcarrier. At least one of the plurality of home-side devices receives the plurality of downlink subcarriers from the station-side device, demodulates a demodulatable downlink subcarrier among the plurality of downlink subcarriers, and transmits the uplink subcarrier to the station-side device. The total number of downlink subcarriers that the station-side device can transmit is less than the total number of uplink subcarriers that the station-side device can receive.