Multiband DFT-S-OFDM for Fiber Nonlinearity Mitigation
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Solution Overview
Problem
Optical Fiber nonlinearity causes significant signal distortion in coherent optical Orthogonal Frequency Division Multiplexing (CO-OFDM) due to high peak-to-average power ratio (PAPR), limiting its practical implementation in high-speed fiber optic transmission.
Innovation Solution
A method and apparatus for transmitting and receiving OFDM subcarriers over a nonlinear and dispersive optical channel by reducing PAPR through DFT-spreading and selective mapping algorithms, determining the optimal number of sub-bands based on fiber properties, and using multiband DFT-S-OFDM to mitigate nonlinear distortion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional CO-OFDM is used to achieve high data transmission rates, then productivity is improved, but signal distortion increases due to high PAPR causing nonlinear effects in fiber
Solution Approach 1:
The patent divides the OFDM signal into multiple sub-bands, each processed separately through DFT-spreading. This segmentation reduces the PAPR of individual sub-bands compared to the full-band signal, thereby reducing nonlinear distortion while maintaining high data transmission rates through multiplexing of sub-bands
Solution Approach 2:
The patent applies different processing (DFT-spreading) to different sub-bands locally, optimizing each sub-band's PAPR characteristics. This local optimization allows each sub-band to have improved resistance to nonlinear effects while the aggregate signal maintains high transmission capacity
2Reliability
If PAPR reduction techniques are applied to reduce nonlinear distortion, then reliability is improved, but device complexity increases due to additional signal processing requirements
Solution Approach 1:
The patent transforms the signal from frequency domain to time domain through DFT-spreading, changing the signal representation parameters. This transformation enables PAPR reduction while using standard OFDM processing blocks (FFT/IFFT), avoiding the need for entirely new complex processing architectures
Data Source
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AI summary
A method (1200) of transmitting digital information via a nonlinear optical channel (722), comprises receiving (1202) data (702) comprising at least a portion of the digital information. A plurality of frequency domain symbols is generated (1204) from the data, and each symbol is assigned to one of a predetermined plural number of frequency sub-bands. Each sub-band may be processed separately (1206) to reduce a peak-to-average power ratio (PAPR) of a transmitted optical signal. The optical signal (12) is then generated (1208) comprising the plural number of sub-bands, and transmitted via the nonlinear optical channel (722). The plural number of frequency sub-bands is predetermined so as to reduce nonlinear optical distortion of the optical signal within the nonlinear optical channel relative to a corresponding single frequency band signal. A corresponding information-receiving method, a transmitter apparatus and a receiver apparatus are also disclosed.