Chromatic Dispersion Estimation Using Cross-Correlation Peaks
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Solution Overview
Problem
Existing techniques for estimating wavelength dispersion in optical fiber communications face challenges such as severe distortion from non-linear optical effects using characteristic training signals and slow detection speeds due to sweeping methods.
Innovation Solution
An optical reception device with a single coherent photoelectric converter and analog-to-digital converters, employing a correlation signal generation unit, correlation calculation unit, and dispersion amount calculation unit to estimate wavelength dispersion without characteristic training signals, utilizing frequency domain conversion and band filtering to calculate dispersion based on cross-correlation peaks.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If characteristic training signals with energy localized at specific frequencies are used to determine wavelength dispersion amount, then measurement precision is improved, but distortion through non-linear optical effects becomes severe
Solution Approach 1:
The invention changes the parameter of signal characteristics by using signals without specific frequency localization properties instead of training signals with energy concentrated at specific frequencies. This parameter change allows wavelength dispersion measurement without causing severe non-linear optical effects distortion.
Solution Approach 2:
The invention uses ordinary communication signals that are already present in the system rather than special training signals. These ordinary signals serve as disposable measurement carriers that don't require special properties and don't cause harmful non-linear effects.
2Measurement precision
If sweeping method is used to detect dispersion compensation amount, then measurement precision is improved, but detection speed deteriorates due to long time required for sweeping
Solution Approach 1:
The invention performs preliminary action by using correlation signal generation to pre-process the received signal and create reference signals before the actual measurement. This preliminary processing enables direct calculation of wavelength dispersion amount without requiring time-consuming sweeping operations.
Solution Approach 2:
The invention replaces the mechanical sweeping method with a computational correlation-based method. Instead of physically or sequentially adjusting dispersion compensation parameters and measuring results, the system uses signal processing in the frequency domain to directly calculate the dispersion amount, substituting mechanical iteration with mathematical computation.
Data Source
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AI summary
A wavelength dispersion amount estimation apparatus includes a correlation signal generation unit configured to generate, from a receive signal, a first signal including a main signal of the receive signal and a second signal, which includes an image signal corresponding to the main signal, with a shift by a baud rate of the receive signal relative to the first signal in a frequency domain, a correlation calculation unit configured to calculate a cross correlation of the first signal and the second signal, and a dispersion amount calculation unit configured to calculate a wavelength dispersion amount, based on a position of a peak of the cross correlation.