I have written a simulation tool on MATLAB for various kinds of Phase-OTDRs since 2019 (started as a graduation project and evolved to master thesis in the domain of Faraday effect-based magnetic field sensing by use of polarization properties of backscattered Rayleigh signals/FBG reflections) and followed the literature for 5 years, adapting new interesting demodulation or interrogation techniques to my code if possible. However, our lab (Izmir Institute of Technology, Fiber Optic Sensors Lab) has never gotten a sufficient financial support to buy experimental tools, coherent laser source, EOM, EDFA, etc. although my supervisor tried her best. Thus, it is the first time that I see a real on-lab Phase OTDR demonstration. I felt a childish excitement while you were playing with pulse length, power, central wavelength and observing the Rayleigh backscatter trace. Note: This year, I gave up dreaming of lab facilities and resigned from research assistantship. I am in a radar company now and building radar systems in real, not only in theory :D Seeing that you mention the similarity of radar and OTDR in video description made me smile :)

@yourfavouriteta

29 күн бұрын

@@samil26 That sounds like very exciting work! It would be cool to see what your MATLAB code is capable of.

@samil26

29 күн бұрын

@@yourfavouriteta Your comment encourages me to record a video to tell about it :D

@yourfavouriteta

29 күн бұрын

@@samil26 Please do! I recommend the free OBS Studio for recording and I have heard good things about DaVinci Resolve for editing (also free).

@Lephysicien1993

7 күн бұрын

That sounds like exciting work!

Hello, which type of filter do you use, please? Is there any website where I can buy it? Thank you very much!

@yourfavouriteta

Ай бұрын

It's an XTM-50 filter from EXFO. Being able to tune both the bandwidth and center frequency is super convenient. I think that they cost around USD8.000; not unusual for a specialized piece of research equipment.

@Lephysicien1993

Ай бұрын

Thank you. Do you recommend another cheaper tunable filter?

@yourfavouriteta

Ай бұрын

@@Lephysicien1993 Hmm it depends on what specs you need; range, bandwidth etc. The cheapest option would probably be to build a temperature stabilized box with an FBG in it; takes some time to tune and has a fixed bandwidth, which is inconvenient, but otherwise pretty simple. Found some FP filters here in the USD2000 range: wdmquest.com/collections/tunable-optical-filter

@Lephysicien1993

7 күн бұрын

@@yourfavouriteta I made a Phi-OTDR system with a 3 MHz laser at 1550 nm based on the article "A Distributed Optical Fibre Dynamic Strain Sensor Based on Phase-OTDR" by A. Masoudi, M. Belal, and T. P. Newson. The system is based on an MZI interferometer. However, what I see on the oscilloscope are two pulses: one corresponding to Fresnel reflection at the end of the fiber and another within the fiber i think at X=0m (which I don't understand the origin of).The problem is that I don't see the same results you obtained; I don't even see the backscattering trace like an OTDR trace. Do you have any suggestions?

@yourfavouriteta

7 күн бұрын

@@Lephysicien1993 The detection scheme in that paper is more advanced than the one I present in my video, which may explain why you get a different signal than me. I recommend trying to build my more basic setup before attempting to recreate the one in the paper. In my experience, mastering the basics early always pays off in the long run. One thing you may want to verify is the duration of the pulses you use and the repetition rate. First of all, the temporal duration, D, of the pulse should be such that Dc/2