Journal: Nature Communications

Article Title: Photonic-electronic arbitrary-waveform generation using quadrature multiplexing and active optical-phase stabilization

doi: 10.1038/s41467-025-61564-w

Figure Lengend Snippet: As a performance metric, we use the SNDR estimated from received PAM symbols (SNDR PAM ). a SNDR PAM penalty as a function of the LO-to-signal power ratio (LOSPR). The penalty is measured with respect to the optimum LOSPR of 14.5 dB and initially decreases with increasing LOSPR, because the residual signal-signal beat interference (SSBI) decreases. b Peak-to-peak voltage swing measured at the PE-AWG output as a function of the LOSPR. Since the electrical output power grows with decreasing LOSPR, a trade-off between output voltage swing and signal quality needs to be made. The yellow stars in Subfigures ( a ) and ( b ) correspond to the levels used in the subsequent measurements shown in Subfigures ( d ) and ( e ). c Simulated SNDR PAM penalty for BPD skews between 0 and 2 ps and for different LOSPR levels as indicated by the different colors. We find a SNDR PAM penalty of 0.9 dB for a LOSPR of 8 dB and a skew of 0.7 ps as specified for the BPD used in our experiments. We hence conclude that the skew results mainly from a path-length mismatch between the two fiber pigtails connected to the BPD, such that future integration of the PE-AWG can improve the SNDR PAM . d SNDR PAM levels achieved for generating PAM waveforms at various symbol rates with the PE-AWG and with several other waveform generators, comprising both commercially available AWGs , , as well as other research-type waveform generators , – . Square markers refer to results obtained in electrical back-to-back measurements, whereas circular markers represent optical back-to-back experiments. In case of the PE-AWG, we compare the SNDR PAM for the case without and with an adaptive equalizer ( L = 100 taps) used to remove residual inter-symbol interference, see the associated square markers with white filling and colored filling, respectively. The PE-AWG relies on Keysight’s AWG model M8194A (red star) and offers a signal quality that is on par with that offered by some commercially available waveform generators such as the Keysight M8199A or the Micram DAC5, while featuring a much higher usable bandwidth than these devices. At symbol rates beyond 140 GBd, the PE-AWG is only outperformed by Keysight’s most recent AWG model M8199B (green markers), which was not available as a signal source for our experiments at the time they were conducted. e Average voltage swing observed at the PE-AWG output for RRC pulses with a spectral roll-off of ρ = 0.05. We achieve decent voltage swings between 250 and 300 mV pp irrespective of the symbol rate.

Article Snippet: This notion is supported by the fact that, following the introduction of Keysight M8194A based on 16-nm CMOS , all further AWG generations have relied on 55-nm BiCMOS circuits while leveraging complex analog front-ends for combining two underlying DAC channels .

Techniques: