08-01-2013, 12:27 PM
FIXED FREQUENCY GRID-DWDM
FIXED FREQUENCY.pptx (Size: 68.12 KB / Downloads: 25)
WHY OPTICAL COMMUNICATION?
Major demand in communication:
More information capacity
Capacity is proportional to Bandwidth of the channel.
Copper wire carry signals upto 1MHz.
Coaxial cable-100MHz.
Optical fiber-50THz.
Higher the carrier frequency greater the bandwidth.
Optic fiber communication uses light-a carrier with the highest frequency.
Light frequency-100 to 1000 THz.
A fiber optic communication link can carry upto 300,000 channels simultaneously.
NEED FOR MULTIPLEXING
Transmission distance is limited by fiber distortion and nonlinear effects.
Transmission system uses only a small portion of transmission capacity.
Multiplexing – entails the transmission of several signals over the same channel.
Fixed frequency grid- Dense Wavelength Division Multiplexing(DWDM) were used.
FIXED FREQUENCY GRID-DWDM
DWDM technique currently supports 200 GHz, 100 GHz, 50 GHz, and 25 GHz wavelength spacing.
Drawbacks of the fixed frequency grids (or fixed wavelength spacings):
Poor fiber spectrum utilization.
Shows difficulty in supporting super-channels.
Limits the adaptability of bandwidth and optical reach of an optical channel.
MINI-GRID AND GRIDLESS
To eliminate the above shortcomings and achieve high spectral efficiency for the next-generation optical transport network;
Strategies based on:
a) Mini-grid spectrum utilization wavelength spacing is largely reduced.
or
b) Gridless spectrum utilization centre frequency can be anywhere on the spectrum.