Performance analysis of free space optical communication in open‐atmospheric turbulence conditions with beam wandering compensation control

A Review–Unguided Optical Communications: Developments, Technology Evolution, and Challenges

“…This standard offers fast information rates [143], quality of service (QoS) [144], and wide coverage compared to WLAN [145,146]. WiMAX was launched in 1999 to provide the conditions for wideband wireless metropolitan area networks [147]. In 2001, 802.16 received the first nod, and then three more improving standards: 802.16a, 802.16b, and 802.16c, followed it [148][149][150].…”

Extraction of Doppler signature of micro‐to‐macro rotations/motions using continuous wave radar‐assisted measurement system

“…The signal tapped from the power splitter acts as a reference signal and it gets superheterodyned with the received RF signal, as per (1)-(3), to get the baseband signal and/or determine the Doppler frequency (f d ). The received radar signal is applied into a data acquisition system which is designed with a baseband filter and amplifier (LM358), bipolar analogue to digital converter (ADC) [33] and digital circuit built in a field programmable gate array as shown in Fig. 2.…”

Historical perspective of free space optical communications: from the early dates to today's developments

“…short-distance FSO systems, the light carrier beam with wide divergence rather than narrow one is more appropriate because the impact of time varying atmospheric channel effects is not a part in it and its performance fully depends on the Tx power, channel loss and sensitivity of the optical detector. The outdoor FSO link covers a long distance in the order of kilometres using the atmospheric channel as a medium of communication [14,26]. Most-common modulation schemes that are being used in FSO communication are on-off keying, differential phase shift keying, digital pulse width, digital pulse position, and digital pulse interval modulations [9-11, 15, 27].…”

“…3. Water droplets and aerosol particles formed by vapours of size of a few hundred microns and they can alter the characteristics of propagating optical wave, completely hamper it, degrade the wave front quality, which may result in the signal loss and/or fluctuations of the signal intensity/phase caused by their combined interactions of absorption, scattering, and reflection [9,10,[26][27][28], thereby limiting the link availability with increased system BER [19,26,27,36]. Fog substantially attenuates visible and near-IR radiations.…”