All-optical waveform sampling

In this paper, we will focus on optical waveform analysis based on all-optical sampling. In contrast to the case when using a fast-photo diode and electronic sampling this approach not only can have very high temporal resolution but also eliminates ringing artifacts that arise from non-ideal impedance matching in the electronic case. We rely on the use of four-wave mixing in a highly nonlinear fiber acting as a sampling gate. We expanded the approach above and by using four separate gates, each sampling different parts of a waveform at 25 GHz, we achieved real time sampling with a Nyquist limited bandwidth of 50 GHz. The concept was also extended to phase-sensitive mode by adding a local oscillator for coherent detection allowing constellation diagram analysis at 40 Gbaud.