Nonlinear Compensating Apparatus for Optical Fiber Transmission
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Solution Overview
Problem
Current optical communication systems face significant challenges in mitigating intra-channel nonlinearity, particularly for NRZ codes, leading to timing jitter, signal amplitude fluctuations, and ghost pulse generation, especially at high data rates, where existing methods are not effective in improving system performance.
Innovation Solution
A nonlinear compensating apparatus and method that acquires a symbol information sequence, calculates a weighted sum of interaction items of pulses, rotates the perturbation quantity by a predetermined phase, and compensates the symbol information sequence to transmit signals, thereby mitigating nonlinearity effects in optical fiber transmission.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If simple intensity modulation formats are used, then device complexity is reduced, but signal to noise ratio is insufficient requiring higher input power which increases nonlinearity cost
Solution Approach 1:
The patent applies preliminary action by pre-compensating the signal at the transmitting end before transmission. The nonlinear compensation apparatus calculates perturbation quantities based on symbol information sequences and applies corrections in advance, so that the signal arrives at the receiving end already compensated for nonlinear effects, eliminating the need for complex post-processing while maintaining high signal quality
Solution Approach 2:
The patent introduces an intermediary compensation mechanism that mediates between the simple modulation format and the required signal quality. The nonlinear compensation apparatus acts as an intermediary device that processes the simple intensity modulated signal, adding perturbation correction terms that bridge the gap between simple modulation and high signal-to-noise ratio requirements
2Reliability
If higher input power is used to ensure sufficient signal to noise ratio for complex modulation, then signal to noise ratio is improved, but nonlinearity cost increases
Solution Approach 1:
The patent converts the harmful nonlinear effects into a beneficial compensation process. By calculating perturbation quantities that represent the expected nonlinear distortion and applying opposite corrections, the system transforms the harmful nonlinear interactions into a predictable and compensatable effect, allowing operation at lower power levels while maintaining signal quality
Solution Approach 2:
The patent applies preliminary anti-action by pre-calculating and applying compensation for nonlinear effects before they fully manifest. The nonlinear compensation apparatus computes perturbation terms based on symbol sequences and link parameters, then applies corrections that counteract the expected nonlinear distortion, preventing rather than merely correcting the harm
3Device complexity
If prior art nonlinear compensation method is used, then device complexity is reduced through double oversampling, but performance is not good for NRZ codes
Solution Approach 1:
The patent applies parameter changes by modifying the perturbation calculation approach specifically for NRZ codes. Instead of using the prior art's double oversampling method, the patent changes the calculation parameters to work with single-rate NRZ sequences, computing perturbation quantities based on adjacent symbol interactions in the original sampling rate, which significantly improves NRZ performance while maintaining simplicity
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution significantly improves the performance of NRZ codes by compensating for symbol information, shaping pulses, and transmitting signals that remain undamaged after nonlinear effects, applicable to single polarization and polarization multiplexing systems, and compatible with various modulation formats.
Implementation Method 1
The intra-channel nonlinearity is inherent damage in an optical transmission system and is originated from the Kerr effect
Data Source
AI summary
The present invention provides a nonlinear compensating apparatus and method and a transmitter. The nonlinear compensating apparatus includes: an information sequence acquiring unit, configured to acquire a symbol information sequence of the pulse signal; a perturbation quantity acquiring unit, configured to calculate the weighted sum of interaction items of pulses on one or more moments relative to the current moment, to obtain the perturbation quantity produced on a transmission link with a certain length, and rotate the obtained perturbation quantity by a predetermined phase; and an information compensating unit, configured to calculate the difference between the symbol information sequence and the perturbation quantity to obtain a compensated symbol information sequence. With the embodiments of the present invention, the performance of the system, especially the performance of NRZ (Not Return to Zero) code, may be further improved.