Digital to Analog converter

[Jamal]

Hi all,
I am trying to implement an analog to digital converter using photonic sampling and electronic quantizing. For that I have implemented a 16GHz laser source(in the subsystem) and sampled an ASK signal of 6GHz using MZM Modulator.
After sampling I have quantized the signal and converted it back to an analog signal using built in Digital to Analog Converter component. But the problem is that the output of DAC is not the same as that of ASK Modulator. There seems to be some problem with reconstruction. There are a lot of fluctuations in signal. Can anyone explain the reason for these fluctuations and how to avoid them ? I have also attached the osd file.

Attachments:

1. MZM-Sudebands-with-ASK-signal-oversampled-without-SMF1.osd

[Damian Marek]

If you inspect the spectrum of the signal after the PIN Photodiode you will notice the signal extends passed 40 GHz and thus requires a sampling frequency of at least 40 GHz to reproduce the signal. Re-sampling at 16 GHz will not give a good signal.

The reason why this ~6 GHz electrical starting signal needs a full 40 GHz to reproduce it comes from the fact that signal is modulating a large bandwidth carrier signal (the multi-wavelength source).

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