Fig. 2: 100 Gbit s−1 and beyond OOK signalling.

a Experimental setup for generating OOK signals from our fabricated SPH modulator. PPG pulse-pattern generator, MUX electronic multiplexer, AMP amplifier, VOA variable optical attenuator, BPF optical band-pass filter, EDFA erbium-doped fibre amplifier. Inset shows the applied driving electrical 100 Gbit s−1 OOK signal with a peak-to-peak voltage of 2.0 V. b Photograph of the experimental setup for testing high-speed operation up to 120 Gbaud. c, d Measured optical eye diagrams of OOK signals at data rates of 100 Gbit s−1 (c) and 120 Gbit s−1 (d). The corresponding Q factors are 7.3 and 5.4, respectively. e Measured BER curves as functions of the received optical power (ROP) for 90, 100 and 110 Gbit s−1 OOK signals. The pre-FEC BER thresholds for hard-decision (HD) and KP4 FECs42, that is, 3.8 × 10−3 and 2.2 × 10−4, respectively, are also plotted for reference.