Chirped return-to-zero modulation by imbalanced pulse carver driving signals

We demonstrate a simple way of generating chirped and alternate-chirp return-to-zero signals of various duty cycles by means of a sinusoidally driven dual-drive Mach-Zehnder modulator. The amount of inherently bit-synchronized chirp is tuned by varying the imbalance of the drive signals' amplitudes or their relative delay. High temporal resolution measurements of the intensity and phase of the modulated optical field are obtained at 20 and 40 Gb/s using the spectrogram technique.