Method for enhancing optical signal-to-noise ratio measuring precision by correcting spectral resolution

A method for enhancing optical signal-to-noise ratio (OSNR) measuring precision by correcting spectral resolution, the method comprising steps of:

• (1) obtaining actual powers PAi of a series of broad spectrum signals which have a central wavelength of λ, a bandwidth of Δλ1, a power interval of ΔPz, and a power range of (Pmin-Pmax), wherein, i=1, 2, . . . , n;
• z=1;
• Pmin is the minimal power of the broad spectrum signals;
• and Pmax is the maximum power of the broad spectrum signals;
• (2) measuring a calibration spectrum of each signal for the series of broad spectrum signals by using optical spectrum analyzer (OSA), adding up powers of sampling points which fall into spectrum range having the central wavelength of λ, the bandwidth of Δλ1, to obtain a sum of powers of the sampling points, to obtain a series of sums PBi for the series of broad spectrum signals, wherein, i=1, 2, . . . , n;
• (3) obtaining corrected resolutions Resi=PBi·Δλ2/PAi according to the actual powers PAi of the series of broad spectrum signals, the series of sums PBi of powers of the sampling points, and a wavelength interval Δλ2 between adjacent sampling points;
• (4) obtaining a fitting expression according to the corrected resolutions Resi and the series of sums PBi of powers of the sampling points by a least squares method;
• (5) obtaining a series of corrected resolutions RES′i after being fitted according to the series of sums PBi of powers of sampling points and the fitting expression;
• obtaining measured powers of the series of broad spectrum signals P′Ai=PBi·Δλ2/RES′i according to the series of corrected resolutions RES′i after being fitted, the series of sums PBi of powers of the sampling points, and the wavelength interval Δλ2;
• (6) according to the actual powers PAi and the measured powers P′Ai of the broad spectrum signals, obtaining relative errors
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• and determining whether the following formula
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• is satisfied;
• if yes, performing step (7);
• or else, making ΔPz=ΔPz/2, z=z+1, and repeating steps (1)-(5), wherein, 0<ε<1;
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• (7) measuring a spectrum of a signal under test, so as to obtain the corrected resolutions corresponding to the sampling points required by calculating OSNR in the spectrum;
• and obtaining OSNR based on the corrected resolution.