Sample rate make change in result for optical fiber simulation ?


#1

Hello,

I’d like to make a simulation as in figure below:

and here is a result:

So I wonder that the system need a little bit time at the beginning to generate an output signal as we see in result, let call this time is t. When I change a sample rate ( call as f_s) in root element property, the value of t also change, and I realized that I always get the relation between t and f_s is t*f_s = 32. My question is why sample rate has strong effect to my result like that, and does 32 has any meaning, if yes, what is the meaning of this value?
p/s: I only get this effect when used optical fiber.

Thank you for your help.


#2

Hi @tdo01,

This delay is caused by the digital filter used in the fiber model.

The default number of taps for the digital filter is 64, so you will get 32 samples of delay. The relation is:

t = (1/f_s) * #taps / 2;

That’s why you always have t*f_s = #taps/2 = 32. If you change the number of taps of the filter or the sampling rate, the delay will be changed as well. And we recommend to use at least four times of samples per bit number of taps for accurate simulation:

number of taps = 4 * samples per bit;

In the next release, we are going to introduce block mode simulation for the fiber model and users won’t need to worry about the digital filters any more (and the delay effect will no more exist). Stay tuned :slight_smile:


#3

Hi @gwang,

Noted it ! Thank you very much for your help.


#4

Hi @tdo01,

To follow up our discussion before, the Block Mode simulation is now available in INTERCONNECT since R2017a! You could find mode information about it through the following link and example:

Transmission analysis: https://kb.lumerical.com/en/index.html?solvers_transmission-analysis.html

I hope this could be useful for your design. I’d love to discuss more on this if you have further inquires :slight_smile:


#5

Hi @gwang,

Thank you for your new information. I downloaded INTERCONNECT R2017a and also the latest version of the license manager, but when I tried to use block mode, I got a problem is " Error obtaining the license for block mode" as in figure below, but my license will expires at 8/31/2017. Could you help me to solve this problem. Thank you very much for your help !


#6

Hi @tdo01,

Actually this Block Mode simulator requires an additional license to the standard INTERCONNECT license. Please contact sales@lumerical.com to request for an extended evaluation license, and it will be issued to you shortly.

I hope this could help. Please let me know if you have further problems.