A Mach–Zehnder modulator based novel regenerator for employment in relays used in free space optical communication

Abstract

Relay nodes that are proposed for extending the length of free space optical links are generally based upon simple optical amplifiers. In this article, we 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 compress 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 modeled by the Gamma–Gamma 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 0.5×10−14 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 0.7 dB under medium turbulence conditions, respectively.

Duplex Baseband Signal Transmission Over Free Space Optical (FSO) Link Employing Carrier Reuse

“…However, recent technological developments with successful results make it practical to explore the advantages of the high bandwidth [12]. The transmission in FSO is dependent on the medium because of the presence of foreign elements like rain, fog, haze, physical obstruction, scattering, and other atmospheric turbulence.…”

Duplex Baseband Signal Transmission Over Free Space Optical Link Employing Carrier Reuse

“…The geometrical losses, pointing and tracking errors overshadows the FSO links' reliability, resultantly, reducing link range and the performance bit error rate (BER) [12]. In [13,14], the authors proposed optical relays and regenerative relays to mitigate atmospheric attenuation and turbulence-induced fading. Despite, these mitigation techniques, a hybrid FSO/RF parallel link is an excellent choice [15,16].…”