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1. (WO2018197975) NOISE-FREE MEASUREMENT OF THE SPECTRAL SHAPE OF A MODULATED SIGNAL USING SPECTRAL CORRELATION

Pub. No.:    WO/2018/197975    International Application No.:    PCT/IB2018/052423
Publication Date: Fri Nov 02 00:59:59 CET 2018 International Filing Date: Sat Apr 07 01:59:59 CEST 2018
IPC: H04B 10/07
Applicants: EXFO INC.
Inventors: CYR, Normand
HE, Gang
RUCHET, Bernard
Title: NOISE-FREE MEASUREMENT OF THE SPECTRAL SHAPE OF A MODULATED SIGNAL USING SPECTRAL CORRELATION
Abstract:
Method and systems for characterizing an optical signal propagating along a communication link are disclosed. The signal includes a data-carrying signal contribution, modulated at a symbol frequency, and a noise contribution. The method includes measuring an optical power spectrum of the signal, which includes a data-carrying signal spectrum component and a noise spectrum component. The method also includes determining a measured spectral correlation function within pairs of spectral components of the signal as a function of center frequency of the pairs, the spectral components in each pair being spectrally separated from each other by the symbol frequency. The method further includes obtaining a solution for the data-carrying signal spectrum component based on the measured optical power spectrum, such that a calculated spectral correlation function based on the solution matches the measured spectral correlation function. In some embodiments, the spectral correlation function is measured as a low-frequency beatnote amplitude function.