Abstract:
Relay nodes that are proposed for extending the length of free space optical
links are generally based upon simple optical amplifiers.In this thesis i have
proposed an all-optical relay that performs regeneration of optical signals
along with the conventional optical amplification. Our proposed regenerator
is based upon a dual-drive Mach-Zehnder modulator. The optical pulsed
signal received at the input of the regenerator is divided into two outputs
using an optical splitter. One of the splitter outputs is converted into an
electrical signal while the signal in the other path is given as input to the
optical modulator. The negative slope of the modulator is used to com press intensity fluctuations over the pulsed optical signal by combining the
converted electrical signal with the bias voltage of the modulator. We have
compared the performance of our proposed regeneration scheme with the conventional optical amplifier based relay nodes in a free space optical link that
is modelled by the GammaGamma channel model. To simulate the effect of
medium and strong turbulence of the free space optical link, the refractive
index structure parameters chosen for the Gamma-Gamma channel model
are 0.5×10−14m−2/3 and 0.5×10−9m−2/3, respectively. It was observed that
our proposed dual-drive Mach-Zehnder modulator based relay significantly
improves the receiver sensitivity by 4 dB under strong turbulence conditions
and by 0.7dB under medium turbulence conditions, respectively.
