| 摘要 |
<p>Various methods and apparatuses are provided for performing a radix-M FFT (Fast Fourier Transform) upon N time domain samples to produce N/S frequency domain samples for detecting tones of dithers impressed on channels of a WDM (wavelength Division Multiplexed) optical signal. Successive tones have a tone frequency spacing, Δfta, and a sampling frequency, fs, is chosen so that fs = NΔfta/S. S is a spacing given by S = Mw with w being an integer. The radix-M FFT is performed in k = log¿M?(N) stages and within the stages a reduced number of radix-M computations, when compared to the number of radix-M computations of a conventional radix-M FFT, are performed on data points associated with the N time domain samples. This is possible because successive frequency domain samples of the N/S frequency domain samples differ by Δfta = SΔf where Δf is a frequency bandwidth.</p> |
