TY - JOUR N2 - 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. L1 - http://journals.pan.pl/Content/89975/PDF/Journal10178-VolumeXIXIssue3_13.pdf L2 - http://journals.pan.pl/Content/89975 PY - 2012 IS - No 3 EP - 572 DO - 10.2478/v10178-012-0049-0 KW - laser KW - modulation width KW - frequency measurement KW - optical frequency synthesizer. A1 - Křen, Petr PB - Polish Academy of Sciences Committee on Metrology and Scientific Instrumentation DA - 2012 T1 - Laser frequency counting and frequency modulation width measurement from a fft signal SP - 565 UR - http://journals.pan.pl/dlibra/publication/edition/89975 T2 - Metrology and Measurement Systems ER -