Select Page
Forum Options

Home Forums GENERAL Differential Group Delay

# Differential Group Delay

(joined December 2015)
Participant

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

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
alistu
Participant

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

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
alistu
Participant

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).