Fiber optic current sensors

  1. Hello..I'm a undergrad student from hyderabad ,India. Presently I'm am doing a theory based research project on fiber optic current sensors ..which are mainly used to sense current in substations .

    Recently i got a paper when i googled on the net. It was titled Temperature and Vibration Insensitive Fiber-Optic current sensor(pdf file attached ). In this papers two configurations of FOCS are discussed

    -fiber-optic current sensor with 1.Sagnac interferometer configuration
    2 .Reflective configuration

    As I'm still graduating ..i dont have a deep knowledge on these configs but howevr im aware of the basics of fiber optics and communications

    Can anyone explain the following :

    1.these two configs in detail...also differences between them ,pricniples of operation,current ratings measured by each..advantages and disadvantages etc

    2.paper explanation in detail..

    Hoping for positive replies...please help. i need this info ASAP (link to pdf)
    Last edited by a moderator: Mar 2, 2012
  2. jcsd
  3. rude man

    rude man 5,399
    Homework Helper
    Gold Member

    You are asking for a great deal here!

    I will only summarize: both configurations depend on the Faraday effect, which basically states that there is a nonreciprocal phase shift induced between the counterpropagating beams. The light must be circularly polarized, as I recall (not sure anymore about this). Since a current develops a static or quasi-static magnetic field, this phase shift is a measure of the current's intensity. You will need to do a good deal of reading on how this phase shift iselectronically processed (the path lengths are ac-modulated and phase-sensitively demodulated, etc.)

    In the "Sagnac" configuration (and BTW the Sagnac effect itself is a source of error here), light is launched into both fiber coil ends, then ther two emerging beams are allowed to interfere with another to determine the phase shift. In the case of the reflectng configuration, resonance is set up in a closed fiber optic coil, but again the phase shift indicates the magnitude of the current.
  4. I went thru the paper again ..even i analyzed that i had asked for more sorry for that..
    and btw you said that i have to do a lot of reading on how phase shift is electronically can you tell me the source of that info... please suggest ..any book or online

    btw thank you for the above info!!
    Last edited by a moderator: Mar 2, 2012
  5. rude man

    rude man 5,399
    Homework Helper
    Gold Member

    The classic is a book by the German publisher Springer-Verlag (it's in English). It contains many of the early and best papers on the subject, by many authors. But I warn you, it's expensive. UIt may be out of print by now. And it does not address current sensing.

    Also very good is the book by Herve LeFevre:

    I found this on the Web, looks excellent, is encompassing, and incredibly it's free:

    Beyond that I suggest you also do some googling.
  6. thank you for the info..btw can you tell me how temperature affects this type of optical sensor??
    Last edited by a moderator: Mar 2, 2012
  7. vela

    vela 12,443
    Staff Emeritus
    Science Advisor
    Homework Helper

    Rude man has given you a starting point. You need to do your own research now.

    Thread locked.
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