A new method of optical frequency beat counting based on fast Fourier transform (FFT) analysis is described. Signals with a worse signal-to-noise ratio can be counted correctly comparing to the conventional counting method of detecting each period separately. The systematic error of FFT counting below 10 Hz is demonstrated and can be decreased. Additionally the modulation width of a frequency-stabilized laser with high frequency modulation index can be simultaneously measured during a carrier frequency measurement against an optical frequency synthesizer or other laser.

JO - Metrology and Measurement Systems L1 - http://journals.pan.pl/Content/89975/PDF/Journal10178-VolumeXIXIssue3_13.pdf L2 - http://journals.pan.pl/Content/89975 IS - No 3 EP - 572 KW - laser KW - modulation width KW - frequency measurement KW - optical frequency synthesizer. ER - A1 - Křen, Petr PB - Polish Academy of Sciences Committee on Metrology and Scientific Instrumentation JF - Metrology and Measurement Systems SP - 565 T1 - Laser frequency counting and frequency modulation width measurement from a fft signal UR - http://journals.pan.pl/dlibra/docmetadata?id=89975 DOI - 10.2478/v10178-012-0049-0