Demonstration of endless phase modulation for arbitrary waveform generation

We have developed a novel modulation scheme for shifting the frequency of an optical beat signal by improving a conventional serrodyne system via time division multiplexing. This novel method acts as an endless phase modulator where the phase linearly increases from zero phase to infinite phase. With this method, we have shifted a 25-GHz carrier continuously up to 1-MHz offset with 43-dB spur-free dynamic range, which is 7 dB higher than an ordinary serrodyne method.