3 results about "Residual carrier" patented technology

The invention belongs to the technical field of optical fiber communication and coherent optical communication, and discloses a multi-residual carrier modulation method, demodulation method and system. The system comprises a transmitting end and a receiving end, the transmitting end comprises a mapping module and a modulator; the mapping module is used for modulating and mapping a to-be-sent digital signal and generating a corresponding modulation signal; the modulator modulates an optical carrier according to the modulation signal to obtain a modulated optical signal; introducing an optical carrier component comprising a plurality of optical carriers into the modulated optical signal to form a composite optical signal comprising the modulated optical signal and a residual carrier component; the receiving end comprises a detection module, a compensation module and a signal recovery module; the detection module performs beat frequency on the received composite optical signal and local oscillation light to realize coherent detection to obtain an electric signal; the compensation module compensates the electric signal; and the signal recovery module filters the compensated signal, and performs phase noise compensation on the signal by using any residual carrier component in the residual carrier components obtained by filtering to obtain a signal after phase recovery.

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 low-orbit satellite spread spectrum orthogonal frequency division multiplexing frequency offset estimation method based on a carrier loop, and belongs to the technical fields of satellite communication and signal processing. The method comprises the following steps: a receiver divides an integral frame sequence into multiple accumulation blocks with the same structure in time sequence; phase rotation factors of residual carriers corresponding to each symbol period in a current accumulation block are calculated respectively; carrier stripping values and carrier correlation values of each subcarrier in each symbol period in the current accumulation block are calculated in turn respectively; accumulation correlation values corresponding to each subcarrier in the current accumulation block are calculated respectively; the carrier loop state of the current accumulation block is judged according to the index of the current accumulation block, and the carrier frequency control word of the next accumulation block is calculated; the processing of all accumulation blocks is iterated, and the average value of all carrier frequency control words obtained after the carrier loop converges is taken as the frequency offset estimation value of the integral frame sequence. The application can provide high-precision and continuous stable frequency observation values.