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Differential Group Delay

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(joined December 2015)
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Hi All,

What is the different between the Differential Group Delay and the signal time delay. there is parameter in the optical fiber called Differential group delay (ps/km). if I set the length of the fiber to 100km and the differential group delay to 0.2. is that mean the optical signal will be delay or advance by 20ps.

Responses (3):

    • #28889
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      Hi All,

      What is the different between the Differential Group Delay and the signal time delay. there is parameter in the optical fiber called Differential group delay (ps/km). if I set the length of the fiber to 100km and the differential group delay to 0.2. is that mean the optical signal will be delay or advance by 20ps.

    • #28890
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      alistu
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      Hi Mohammad,

      The word “differential” in differential group delay refers to the difference in propagation time between the x polarization axis and y polarization axis. So in 100 km, you’ll have 20ps time difference between x-pol. and y-pol. signals.

      Signal time delay means that the determined delay is applied to the whole signal.

      Regards

    • #28891
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      Hi Alistu,

      Thanks for your reply, do you know how can I calculate the time delay for the signal.

      I tried to check the optical signal before and after the optical fiber using optical time vir. and I found the time different between them is half of the differential group delay.

      • #28900
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        alistu
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        Hi Mohamed,

        The time delay of the signal is dependent on the dispersion parameter, and the dispersion parameter is wavelength dependent, which causes a pulse broadening (as for different wavelengths, the delay is different). I don’t know if it can be calculated using some formula, but maybe it can be done using dispersion of elements with least delay (I have never tried it though).

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