distributed fiber optic acoustic sensor

[NEETHU N]

Hi all, I am simulating a distributed acoustic sensor in optisystem. For that, how can I produce vibration signal of purticular frequency?? Or is it possible using MATLAB?

[Mohamed A. A. Abouseif]

Hi Neethu, as I answered a similar question, here is my answer.

I think you have to go to next step of the sensor.
I mean the vibrational signal will change what in the fiber??
let us say, it will change the loss level, so the output power will fluctuate according to the vibrational signal.
so you can design your system in such a way that, make the output power is dependent on a variable (global variable for example) representing the output power!
Hope that is clear to you and helpful,
thanks
Mohamed Abouseif

[NEETHU N]

Ok sir.
So in which software I can do that? And also, can I make a relation between that variable and the vibration frequency I was intended to use??

[Mohamed A. A. Abouseif]

Neethu,
I mean OptiSystem.
you can define a global variable in the main window then relate it to the vibration frequency as you want.

If that not clear, up load your project and let someone try to help,

Hope that is beneficial

Mohamed Abouseif

[NEETHU N]

Sir, I attach here the osd file. It has a MATLAB component. So attaching its code also.

An LFM signal is created and mixed with laser light- thats what I did upto now. Actually the project is to send this light through fiber and analyse the
backscattered light after interaction with the vibration signal.

[Mohamed A. A. Abouseif]

Hi Neethu,
I think you forgot to upload the .osd file!!

Mohamed Abouseif

[NEETHU N]

SIR ,PLEASE FIND THE ATTACHED

[Mohamed A. A. Abouseif]

Hi Neethu,
I have gone through your project.
two points would make it running.
1. in the matlab file path, do NOT put the file name just put the PATH. as the file name is put in the above edit box.
2. the function you have used in matlab titled “chirp” , I did not see it in matlab. I am not sure what you want to do from this function. check if it is defined or you can rewrite another code to perform what you need.

I have tried your program and it is working now. Just you need to rewrite the equivalent of the chirp function!!

Hope that helps,
Mohamed Abouseif

[NEETHU N]

Sir, chirp function was found from the ‘mathworks’ web sight. I used it to create linear frequency modulated pulses. Is chirp function is different?
https://in.mathworks.com/help/signal/ref/chirp.html.

But there is problems in the plots of signals. It is not like what we are expecting from the command. That is why I interchanged the two frequency values

[NEETHU N]

Yes sir, its working eventhough the the graph(or optisystem visualizer) is not like what is expecting. And it is about the next step I don’t know what to do. ie, get a vibration signal and interact this modulated light with that.

[Mohamed A. A. Abouseif]

good that it is working now.

I think what you need just to emulate the actual vibration effect to the one parameter such as the frequency chirp, or polarization effect …etc.

Hope that helps
Mohamed Abouseif

[NEETHU N]

So, what can I do now.? ,to detect the backscattered light and to check the phase variation of the modulated light by the vbration?

[Author]

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