FSO Optical System Utilizing DPSK Advance Modulation Technique

Free space optical system is a hot topic, which has gaining more and more attention. But, when the signal transmitted in the channel, the performance could be severely degraded due to the atmosphere turbulent. The purpose of this paper is to find a most suitable modulation method for FSO system under FSO channel. The performance of power efficiencies, bandwidth efficiency, BER and SNR for the four modulation schemes have studied and compared in this paper include On-Off keying (OOK), Binary Phase Shift Keying (BPSK), Differential Phase Shift Keying (DPSK) and Quadrature Phase Shift Keying (QPSK) without atmospheric turbulence. Numerical experiments show that BPSK and QPSK schemes are better compared to other schemes in BER performance and power requirements. When take intensity scintillation under Gamma-Gamma turbulence channel into consideration and the average BER is derived with Meijer-G function, BER performances of BPSK and QPSK scheme approximate the same. Compared with BPSK, BER performance for QPSK is 3dB lower. From the simulation results, modulation for BPSK is robust resist turbulence. As a result, BPSK scheme is suitable for free-space optical communication system.

2014

Free Space Optics (FSO) is a promising solution for very high data rate point-to- point communication. Recently, it has received significant attention as a possible alternative to overcome the bottleneck connectivity problem and as a supplement to more conventional RF/microwave links. FSO communications has become attractive for a number of reasons including unlicensed spectrum and a narrow beam width. Moreover, FSO becomes the best solution to solve the problems occurred in conventional wireless system by using optical fiber because it uses laser light to transmit data between two points. The FSO uses beam of light to provide optical connection that can send and receive video, voice, and data information. In this paper Free Space Optical communication concept will be introduced. In addition, the performance of FSO communication link will analysis and illustrates its main challenges and it possible solutions.

Free-space optical communication (FSO) is a revolutionary technology that utilizes optical signals to transmit data wirelessly, providing a viable alternative to conventional wired systems. This paper aims to explore the FSO system, analyze previous research, and discuss the challenges associated with information transmission in FSO networks, particularly under adverse weather conditions that can lead to weakened signals. FSO technology has garnered significant attention due to its numerous advantages, such as high data rates, quick installation, cost-effectiveness, and enhanced security. Many researchers have delved into this field, contributing valuable insights and advancements in the FSO domain. However, one of the major challenges faced by FSO systems is their sensitivity to weather conditions in the vicinity of the transmitter site. Adverse weather factors, such as rain, fog, snow, and dust, can attenuate the optical signals, leading to a reduction in signal strength and potentially affecting data transmission reliability.

Free-space optical communication (FSO) is an optical communication technology which uses light, propagating in free space to transmit data wirelessly for telecommunications. It is point to point infrared spectrum based optical communication between optical transceivers that are separated by physical medium known as air. FSO links use modulated low power laser beams to transmit information through the free space. This technology is useful where a fiber optic cable is impractical. FSO uses the light of wavelength 780nm to 850nm and 1550nm to 1600nm. 1550nm wavelength produce higher power and more eyes safe compared to 780nm and 850nm. The first part of this paper introduces the free space optic system its block diagram and previous research done on free space optics. The second part informs about the atmospheric conditions that effect the free space optical communication. The last part will describes the previous work done using different modulation techniques.

Over the last few decades Free Space Optical (FSO) communication is mostly preferred over the radio frequency communication and microwave communication Systems because of its license-free longrange operations. Also it is having various advantages like small size, high bandwidth, low cost and lease of deployment. Free Space Optical communication has very few limitations also like beam dispersion, scintillation etc. We know that limitation of FSO is the effect of weather conditions on it. In paper we designed to operate at 2.4 Giga bits per second. FSO communication system and presented analysis of 2.4 Gbps FSO system uses different Atmospheric weather condition by distance of 10 km. From the result it seems that as we move clear weather to heavy fog Quality factor as well as transmission range will effectively decrease.

The performance of FSO communication link is subject to numerous atmospheric factors in wireless communication like fog, rainfall, and haze which leads to deteriorate the performance of a system in term of BER and power at the receiver side. Due to numerous advantages of OCDMA over other access techniques, it allows various users to access a channel simultaneously without intervention with the other user. It has the ability to provide security, large number of users, privacy, reduce interference from multiple users and operate asynchronously. So, in this paper, Multi-Diagonal codes along with the fiber brags grating filters for Spectral amplitude coded OCDMA technique is developed for FSO system and performance analysis is performed in terms of BER and received power.

Optik - International Journal for Light and Electron Optics, 2013

In this article, different modulation format RZ, CRZ, CSRZ and NRZ on free space optical communication system has been investigated. It has been observed that external modulation gave us better performance in comparison to direct modulation because direct NRZ spectrum has a strong carrier component compared to external modulated NRZ. Simulation results show that RZ modulation format is best for long distance. Where NRZ is used for short distance and it is less complex, cheaper in comparison to RZ.

Conference on Optoelectronic and Microelectronic Materials and Devices, 2004.

Free space optical communication is an effective means of communication at high bit rates over short distances. Rapid deployment, lightweight, high security, are important features of this system. However, attenuation due to adverse weather conditions & scattering due to turbulence are to be mitigated. In this paper the performance of a short distance FSO link in the presence of atmospheric turbulence has been evaluated.

EPJ Web of Conferences, 2017

Free space optical communication fsoc is vulnerable with fluctuating atmospheric. This paper focus analyzes the finding of new technique dual diffuser modulation (ddm) to mitigate the atmospheric turbulence effect. The performance of fsoc under the presence of atmospheric turbulence will cause the laser beam keens to (a) beam wander, (b) beam spreading and (c) scintillation. The most deteriorate the fsoc is scintillation where it affected the wavefront cause to fluctuating signal and ultimately receiver can turn into saturate or loss signal. Ddm approach enhances the detecting bit '1' and bit '0' and improves the power received to combat with turbulence effect. The performance focus on signal-to-noise (snr) and bit error rate (ber) where the numerical result shows that the ddm technique able to improves the range where estimated approximately 40% improvement under weak turbulence and 80% under strong turbulence.

Free-Space Laser Communications VI, 2006

We report the effect of aerosol-induced local atmospheric heating and the resulting changes in the lower atmospheric optical turbulence on the performance of Free-Space Optical (FSO) communication links. A closed form mathematical expression is derived to estimate the influence of aerosol-induced warming on the Bit Error Rate (BER) of a Binary Phase Shift Keying FSO communication link through Gamma-Gamma modeled turbulence. Our results demonstrate a strong impact, with the aerosol-induced turbulence taking a toll on the signal-to-noise ratio of ~20 dB for a BER of 10 −9. Aerosol-induced warming produces significant variations in BER compared to the clear atmospheric conditions and can subdue the benefits of improved beam alignment.