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Meaning of optical delay

    • Hannah Nguyen


      I am doing with optoelectronic oscillator (OEO) simulation using Interconnect.

      At the first time of doing this simulation, my schematic was not included delay, and I got report of error with no result in RFSA. Then I added delay with 1s and achieved RF signal.

      However, 1 week later, I did my simulation again without delay and I achieved RF signal. I dont understand what happenned with my first simulation. Then, I added delay into schematic in 2 cases: before and after fiber, I achieved the same results(it is reasonable) that obtained higher power than without delay (i dont understand, the power should be lost).

      Could you explain the role of this delay in my OEO simulation?

      Another question is that how I can obtain spurious tones which are caused by fiber length? my results seems too clean to see them. Could I increase the frequency resolution of RFSA to 1kHz but not taking long time of simulation?

      I also include the simulation setup in the second figure.

      Many thanks in advance.

    • Guanhui Wang
      Ansys Employee

      Hi Hannah Nguyen,

      Thank you for the post. For the questions:

      1. About the delay element, I suspect it's because of the INTERCONNECT sample mode simulation method. When the circuit is turned on, all elements start to work. In time domain the signal transfers from one element to another, and the elements wait for the signal will pad 0s at all the ports. Could you please share with us your file for further investigate on this?
      2. I don't think you can resolve such a thin linewidth with a short simulation time. What do you want to measure and maybe we can find some other analytical ways to do this.
    • Hannah Nguyen


      Thank you for your reply. 

      My schematic is a closed loop, it means that the time delay (usually caused by fiber's length) much affects on the signal performance. That's why I dont understand the role of time delay (DLY) component in library. 

      About linewidth, I just want to control the performance of Laser source to check performance of RF signal (for example phase noise). I need frequency resolution of RFSA about 1000 Hz. 

      about sending the file, how can i send my file to you via this forum? here there are only image and insert link place.

      Thank you. 

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