Opt. Express 20, B419–B427 (2012)

Researchers from the University of California in the USA have demonstrated the benefits of employing a high-fidelity cavity-less optical pulse source in an analog-to-digital signal conversion scheme. Their source generates optical pulses in a single pass by using a series of cascaded phase modulators to chirp the light from a continuous-wave 100 mW distributed feedback laser. The chirped light is then compressed into short pulses using a section of dispersion-compensating fibre. They used the resulting 3 ps optical pulses, which had a repetition rate of 2 GHz and a signal-to-noise ratio of over 40 dB, in an analog-to-digital sampling pre-processor, with 8.2 and 7.0 effective bits for analog input signals at frequencies of 0.2 GHz and 40 GHz, respectively. The researchers say their demonstration shows that cavity-less pulse sources are a viable alternative to mode-locked lasers in signal processing applications.