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no image Saturday, June 10, 2017 by Rakesh krishna

Processing DMT signal

I am working towards the design of visible light communications system using DMT signals. I have generated a DMT signal out of AWG(Tektronix AWG 70002A) and amplified it(set up diagram). The amplified signal is DC biased (using tee-bias) and sent to LED for modulation. At the reciver, I have obtained the following traces of DMT signal(shown in segments) over socilloscope(tektronix DP71604). The dmt signal frequency is around 20 MHz and TIA(100 MHz).

The signal has undergone clipping, effected by noise. From the traces (files attached), I belive that envelope of DMT signal is obtained (post photodetection).

How could I process this signal to obtain information about how closer the transmitted and received traces are? I sthe current result decent enough to proceed to processing?

For sure, I need a filter (high pass) at the receiver which is currently not incorporated. I am new to the processing techniques, so i really appreicate any help towards analyzing the received data.



Trace_dmt3june9.png

Comments

  • by  Kevin Angelo Ma (edited)
    Have you heard something called blue optical filter? There are some references that I would like to share with you: * http://proxy.osapublishing.org/DirectPDFAccess/3B2C384A-C505-30AD-01626D4C706D2850_299622/oe-22-17-20646.pdf?da=1&id=299622&seq=0&mobile=no * https://ir.nctu.edu.tw/bitstream/11536/125163/1/000354367700035.pdf The recovery process is quite troublesome if you don't have the proper means of retrieving the data sent.
    • by  Richard Shadbolt (edited)
      Hi, I am not proficient in optical communications, but if you have the received signal as an electrical signal, that has been sampled, then you can perform a DSP analysis on the data. I completed a quick check on the oscilloscope, and you should be able to obtain the sampled data via USB ? DSP analysis should be able provide an FFT of the signal to extract the DMT tones buried in the noise. (hopefully). Does this help ? Regards, Richard.
    • by  Rakesh krishna (edited)
      Thank you, Can you please send me the name/title of the paper from OSA posted above.
  • by  Richard Shadbolt (edited)
    Hi, I am not proficient in optical communications, but if you have the received signal as an electrical signal, that has been sampled, then you can perform a DSP analysis on the data. I completed a quick check on the oscilloscope, and you should be able to obtain the sampled data via USB ? DSP analysis should be able provide an FFT of the signal to extract the DMT tones buried in the noise. (hopefully). Does this help ? Regards, Richard.
  • by  Rakesh krishna (edited)
    Thanks, It is helpful.
  • by  Rakesh krishna (edited)
    Thank you, Can you please send me the name/title of the paper from OSA posted above.

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