There was a correction in the script I used to estimate the frequency noise from the inphase and quadrature component. Attachment #1 shows the frequency noise estimated after the correction.
I have also attached the Matlab script ( I am not able to attach the zip file with data files). I remember, while saving the data, we gave the time duration as 70 s. But while processing the data only I realised that the time domain data is captured only upto 2 s. Even in this case, I would expect the frequency axis to start from 0.5 Hz, but I don't see that in the FM noise plot. Kinldy let me know whther I am doing anything wrong in data proocessing.
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Attachment # 1 show the schematic of the lock in amplifier configuration used in Moku lab. We saved the in phase and quadrature components.
In phase =
quadrature =
where  corresponds to 2 -micron ,  is the delay time in the delay fiber and  .
 is the phase noise of the laser.
From the inphase and quadrature component  value is extracted. So, we are actually extrating the combined effect of phase noise of laser as well the phase noise due to fiber length fluctuations due to environmental fluctuations. ASD of this is converted to frequency noise in Hz/rt Hz. Attachment # 2 shows the frequency noise estimated from two sets of measurements. This curve exhibit a 1/f characteristics from about 240 Hz upto 30 kHz
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[Anchal, Anjali]
We tried the Lock in amplifier in Moku lab for the frequency noise measurement. In this case, the output of the photo detector , after dc block and one stage of amplification, is fed into input 1 of Moku. It gives out the inphase and quadrature component. We have saved the data. I will process the data offline and update later.
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