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group delay introduced by SMF

(joined April 2016)
Participant

A section of SMF introduces a time-delay, thus for different input optical wavelengths, different spectral phases ought to be introduced. In order to demonstrate this phenomenon, I tried two simulation experiments (a and b in attached file 1), but both failed.
Experiment a: a1) and a2) use the same SMF (0.01km, disabled GVD), and the same laser diode except for different frequencies.
a1) LD: fre=193.1THz,linewidth=0,initial phase=0
after SMF transmission, measured spectral phase=1.37rad @193.1THz
a2) LD: fre=193.11THz,linewidth=0,initial phase=0
after SMF transmission, measured spectral phase=1.37rad @193.11THz
As additional spectral phase=SMF group delay*input optical frequency, and SMF group delay is around the same, for different input optical wavelengths, why do they have the same spectral phase?

Experiment b: SMF length=1 m
As the refraction index of fiber core is around 1.5, a time delay of around 5-ns ought to be introduced after 1-m SMF transmission. For comparison, the input and output optical pulses are presented in attached file 2. As can be seen, no time delay exists between two pulse trains.

Attachments:

Responses (1):

    • #70031
      Helen
      Participant

      A section of SMF introduces a time-delay, thus for different input optical wavelengths, different spectral phases ought to be introduced. In order to demonstrate this phenomenon, I tried two simulation experiments (a and b in attached file 1), but both failed.
      Experiment a: a1) and a2) use the same SMF (0.01km, disabled GVD), and the same laser diode except for different frequencies.
      a1) LD: fre=193.1THz,linewidth=0,initial phase=0
      after SMF transmission, measured spectral phase=1.37rad @193.1THz
      a2) LD: fre=193.11THz,linewidth=0,initial phase=0
      after SMF transmission, measured spectral phase=1.37rad @193.11THz
      As additional spectral phase=SMF group delay*input optical frequency, and SMF group delay is around the same, for different input optical wavelengths, why do they have the same spectral phase?

      Experiment b: SMF length=1 m
      As the refraction index of fiber core is around 1.5, a time delay of around 5-ns ought to be introduced after 1-m SMF transmission. For comparison, the input and output optical pulses are presented in attached file 2. As can be seen, no time delay exists between two pulse trains.

      Attachments:
    • #70035
      Profile Photo
      Ahmad Atieh
      Moderator

      Hello Helen,
      How did you measure the spectral phase?
      Could you please try the bidirectional fiber instead of the unidirectional Optical Fiber component?
      please let me know the version of OptiSystem that you are using.
      email me at ahmad.atieh@optiwave.com
      Regards,
      Ahmad

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