Forum: FPGA, VHDL & Verilog Optical Receiver for PPM: Which hardware is best suited?

von David Veit (Guest)

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Dear community,

I am working on a project and I'm having troubles finding the best 
system to solve the problem. My task is to build a wired optical 
communication system with a bit rate of at least 100 MBit/s, better 
would be 1 GBit/s. As Modulation scheme PPM (Pulse Position Modulation) 
is used. For first tests receiver and transmitter can be on the same 
board and therefore share the same clock.

Things I already have available are:
Laser + 10Gbit/s LN Intensity Modulator
10Gbit/s Linear Optical Receiver

What I need are:
- an ADC which can sample the signal I get from the receiver with at 
least 2 Gsps, more would be better. Resolution of the ADC does not 
really matter.
- an FPGA (or anything else) suitable for processing the data from the 
ADC (maybe something like the Xilinx Zynq would be nice because there is 
also an ARM core available for other tasks). Best would be if the ADC is 
on the same board as the FPGA or can be easily connected to it.
- an FPGA (or anything else) to create the information signal for the 
modulator. I think the SERDES of an FPGA might be a good way to do this.

If someone of you has experience doing something like this I would 
appreciate any help.

Best regards,

: Moved by Moderator
von Klakx (Guest)

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When you are using PPM then it has two levels (0 and 1). Do you really 
need a ADC like 8bit-ADC, maybe for echo cancelation or some digital 
filtering? or is a simple comparator sufficient?

Serdes modules from Xilinx or Altera can sample really fast >10Gbit/s.

First question additional ADC or no ADC?

von David Veit (Guest)

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Thanks for the reply.

A comparator would be sufficient for PPM, but I forgot to say that after 
I managed to do PPM the same hardware might be used to try different 
modulation schemes. I don't need the ADC, but it would be nice to have 
the ability to add one later by means of an FMC card or something like 

For now a comparater is enough.

Thanks for the help!


von Klakx (Guest)

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Xilinx or Hitechglobal offer FMC ADC Adapter cards so this way remains 
open for you.
But at first try serdes only, should give you enough Performance for the 
first shot


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