Calculating Delay of Optical Devices [Optical System]

[Damian Marek]

Question:

What is the best way to go about calculating the optical delay associated with components such as couplers, switches and amplifiers?

[Tu Nguyen]

Hi,
I found that sometime the result of optisystem is not so reliable. I dont know why, or is there any problem with my simulation. I just run this sample simulation to calculate the delay but I cant understand why it goes like that.

– look at figure 1, I see that the delay time is ~12.6ns, however, I see in the figure, it should be ~0.2ns.
– at figure 2, I discarded the fiber, and of course, both signal are exactly the same. however, the delay module tells me that there is still 12.8 ns in delay.

What is the point I missed?
I attached the figures and the model as well,
Many thanks if you have a short look.

Attachments:

1. 

   figure1.jpg
   

2. 

   figure-2.jpg
   

1. CalculatingDelay_problem.osd

[Damian Marek]

The clock recovery component looks for the portion of the signals with most correlation, but in some cases when the signal undergoes distortion due to propagation in a fiber the two signals are much different not only from delay. In these cases the clock recovery component will not work.

In your second case the result is a bit more surprising. Try adding a small optical delay, the clock recovery should find this delay no problem. If the signal is exactly the duplicate, which hopefully is quite rare, then there might be some type of numerical error that it does not find the correct 0 time delay.

Regards

[Aabid Baba]

Hello Damian,
i guess optiwave library doesn’t contain any such visualizer. We can introduce delays of our choice but i don’t think we can calculate same for components we use in optisystem.
Anyway, if you ever find how do we calculate delays of components we use , please share.

best Regards

[Aabid Baba]

may be this could help

Differential Mode Delay and Modal Bandwidth

[Chandan Sharma]

Dear Damian, I am using optisystem 13 and I am not able to open your zip file that you have attached for calculating latency of any component. Please attache it again that is compatible with optisystem 13.If you have any other technique to find latency please explain.

[Damian Marek]

Answer:

Depending on the component and its theoretical model, some of the devices may or may not have an associated delay. To measure the delay due to a component or components, take a look at the “CalculatingDelay.osd” file I have attached. Parts a), b), c) below are demonstrated in the project.

a) To graphically compare the delay, place a fork before the components of interest. Use a Dual Port Optical Time Domain Visualizer to plot two optical signals.

b) Sometimes the above is inconvenient as the signal may have been significantly amplified or attenuated. In that case, it is better to rescale the signals for a better comparison. Use the Optical Power Detector component, then rescale both signals (say from 0 to 1) with the rescale option in the component. Next, view the signals in the Dual Port Oscilloscope Visualizer (one must use the oscilloscope because in OptiSystem, the power detector output is classified as an electrical signal).

c) To see a numerical value associated with the delay, convert the optical signals again using the Optical Power Detector component, then use the Clock Recovery component. The delay time will be displayed in seconds (be sure to right click on the Clock Recovery component, select component results, check Disp boxes to show the signal delay).

Incidentally, if the objective is to add a delay to an optical signal, we have the components Phase Shift and Time Delay to do just that.

Attachments:

1. CalculatingDelay.zip

[Joseph Jiang]

dear damian，I HAVE run the osd file you attached.i think it is not the right time delay when the optical fiber is 5km.it should be us level however it is ns level in you project.CAN YOU CHECK IT ?THANK YOU!

[Damian Marek]

Hi Joseph,

The Single Mode Fiber model does not apply the group delay. The delay is purely from the group velocity dispersion and the second order group velocity dispersion. Since the delay in microseconds is quite large compared to the time window the signal would wrap around many times.

To calculate the group delay for a fiber use the Measured-Index Multimode fiber model making sure the option for generating a report is checked in the Numerical tab of the component properties. After simulating the report will give information of the delay for each different spatial mode.

Cheers

[Joseph Jiang]

OK,Damina,i understand you.however,when i use SMF ,WHAT IS THE EXACTLY DELAY AS THE PROJECT YOU ATTACHEND?what is the meaning when calculating delay in your project?thank you!

[Damian Marek]

Those delays are due to the dispersion.

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