Analyzing the Quality of Free Space Optical Signal in Fog: A Case Study of Pakistan (original) (raw)
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Critical Events of Fog Attenuation Using Visibility Data in Lahore, Pakistan
NUST Journal of Engineering Sciences
Free-space optics (FSO) communication system is mature, unique and promising technology which is used in various countries to meet high data rate demand and last mile connectivity. FSO link has a capacity to be utilized as a primary communication links by replacing RF communication systems because of its advantages of unregulated bandwidth, broader spectrum of frequency at low power consumption. Now a days researchers has great interest in this technology because of several features and benefits of larger bandwidth, less power consumption, low installations cost, simple to install, no congestion in spectrum, secure and reliable communication without issues of right of way. In free space optical communication, environment layer is used for signal transmission which can be effected from severe weather conditions like smog, dust, smoke, rain and fog etc. In all these severe weather environments, winter fog is one of the main problem because of it offers high optical attenuation on comm...
Further results on fog modeling for terrestrial free-space optical links
Optical Engineering, 2012
Recent measurement campaigns in Prague, Czech Republic have recorded the specific attenuation caused by fog in terrestrial freespace optical (FSO) links along with visibility, liquid water content (LWC), and integrated particle surface area for operational wavelengths of 1550 and 830 nm. Data recorded during 5 months of measurements has been analyzed in an attempt to validate and improve the empirical models for LWC and visibility-based attenuation and the probability density function (PDF) estimation of the received signal strength (RSS). The results strongly suggest that further attempts in refinement of the empirical modeling for visibility-based attenuation or LWC-based attenuation shall move towards the establishment of a global data bank of fog attenuation measurements in different climatic regions. This data bank can then help develop generic models which could lead to better system design of future terrestrial FSO links. The PDF estimation of RSS puts forth the Kumaraswamy distribution as the best fit for settled continental fog conditions.
Performance of Free Space Optical Terrestrial Link under Dense Fog Conditions
Acta Physica Polonica A, 2018
Free-space optical links use modulated beam of light to transmit high amount of data from transmitter to receiver to get line-of-sight communication link. Free-space optical is cost effective solution to provide higher data rate to end-users. Free-space optical links are also considered as a better alternative to RF links due to their advantages of low power consumption and higher data rate of the range Gbps, and are highly secure to electromagnetic interference. Despite of having all these advantages free-space optical links are highly affected by the severe weather conditions like fog, rain, snow, smoke and dust or aerosol particles suspended in air. Fog is one of a major challenge for free-space optical to achieve carrier class availability and causes high amount of attenuation. In this paper we presented the performance analysis of free-space optical links by estimating signal-to-noise ratio, bit error rate, under fog conditions during winter season in Lahore, Pakistan.
Analysis/Simulation of Unavailability of FSO links due to FOG in Karachi & Lahore
Now a day’s transmission of data using infrared light in free space through laser is keen interest of researchers as compared to traditional fiber optics and RF transmission due to its inherent advantages, such as low cost, easy to install and maintain high bandwidth in license free spectrum, Like other unguided media the local climate degrades the system performance of FSO system. The effect of fog on narrowband (780 nm to 850nm & 1529 nm to 1600 nm) transmission of FSO system is maximum due to the smaller size of particle of water as compared to rain where the size of particle is large. In our proposal of current work the two highly populated metropolitan cities of Pakistan ((i) Karachi-the city with less dense fog & (ii) Lahore-the city with more dense fog) are selected for calculation of signal attenuation due to fog. The statistical measurement of the fog for the whole year is obtained in terms of the Visibility from the secondary data available with civil aviation. On the avai...
Probabilistic model for free-space optical links under continental fog conditions
2010
The error characteristics of a free-space optical (FSO) channel are significantly different from the fiber based optical links and thus require a deep physical understanding of the propagation channel. In particular different fog conditions greatly influence the optical transmissions and thus a channel model is required to estimate the detrimental fog effects. In this paper we shall present the probabilistic model for radiation fog from the measured data over a 80 m FSO link installed at Graz, Austria. The fog events are classified into thick fog, moderate fog, light fog and general fog based on the international code of visibility range. We applied some probability distribution functions (PDFs) such as Kumaraswamy, Johnson S B and Logistic distribution, to the actual measured optical attenuations. The performance of each distribution is evaluated by Q-Q and P-P plots. It is found that Kumaraswamy distribution is the best fit for general fog, while Logistic distribution is the optimum choice for thick fog. On the other hand, Johnson S B distribution best fits the moderate and light fog related measured attenuation data. The difference in these probabilistic models and the resultant variation in the received signal strength under different fog types needs to be considered in designing an efficient FSO system.
Analysis/Simulation of Unavailability of FSO Link Due to FOG in Karachi & Lahore
2012
Now a day's transmission of data using infrared light in free space through laser is keen interest of researchers as compared to traditional fiber optics and RF transmission due to its inherent advantages, such as low cost, easy to install and maintain high bandwidth in license free spectrum, Like other unguided media the local climate degrades the system performance of FSO system. The effect of fog on narrowband (780 nm to 850nm & 1529 nm to 1600 nm) transmission of FSO system is maximum due to the smaller size of particle of water as compared to rain where the size of particle is large. In our proposal of current work the two highly populated metropolitan cities of Pakistan ((i) Karachi-the city with less dense fog & (ii) Lahore-the city with more dense fog) are selected for calculation of signal attenuation due to fog. The statistical measurement of the fog for the whole year is obtained in terms of the Visibility from the secondary data available with civil aviation. On the availability of the statistical measurements the four well known fog attenuation models (i) Krus model, (ii) Kim model, (iii) Al-Naublsi advection model and (iv) Al-Naublsi convection model have been used for calculation of unavailability/ absence of the FSO link. These models have been simulated in Matlab 2011Rb for calculation of fog attenuation. Result shows that FSO is good choice for Karachi city instead of Lahore city because its climate does not degrade the signal power at long distance and availability of link is maximum. This measurement will helpful for implementation of FSO system in Climate of Pakistan.
A Study of Fog Characteristics using Free-Space Optical Wireless Links
A technique for modeling the fog droplet size distributions using modified gamma distribution has been demonstrated by considering two separate radiation fog events recorded in Graz (Austria) and Prague (Czech Republic). The measurement of liquid water content (LWC) and the optical attenuations at visible wavelength are used to form equations to obtain the three parameters of the modified gamma distribution i.e., the slope (Λ), the intercept (N0 ) and the shape parameter (m). Calculated attenuation or LWC from the retrieved parameters are in excellent agreement with attenuation or LWC obtained from the measurement. Hence this method is useful in the study of fog microphysics and in modeling the fog attenuations for terrestrial FSO links in situations when our measurement data contains values of attenuations only, or liquid water content only or both at a particular location. For the two case studies, Graz and Prague, we obtained the DSD parameters Λ=3.547 ± 1.935, N0 =3.834 ± 2.239,...
Characterization of Fog Attenuation for Free Space Optical Communication Link
This paper presents the effect of fog attenuation on free space optical (FSO) communication. The analysis focuses on Al-Naboulsi model (advection, radiation) fog coefficient and effects on visibility. The performance comparison is also done for visibilities (0.5, 1, 5, 10, 25, and 50) km. The result shows that the performance of specific attenuation 50 km is better than the other visibilities in both performance parameters (advection, radiation). On the other the effect of fog attenuation on optical communication link is performance, receiver signal power, link margin, data rate and signal to noise ratio (S/N) are the major interesting design parameters in the current study.
Bit Error Rate Measurement of Free Space Optical Communications under Laboratory Fog Conditions
Abstract—This paper outlines experimental investigation of the fog effect on the bit error rate (BER) performance of the free space optical (FSO) communication link under a controlled laboratory environment. The link transmittance and the received signal Q-factor are measured against different levels of fog densities. The link visibility derived from fog attenuation measurement is used to characterize the fog within the chamber.
… (NOC), 2011 16th …, 2011
This paper outlines the experimental investigation of the fog effect on the bit error rate (BER) performance of the free space optical (FSO) communication link under a controlled laboratory environment. The link transmittance and the received signal Q-factor are measured against different levels of fog densities. The link visibility derived from fog attenuation measurement is used to characterize the fog within the chamber. Moreover, the effect of using different average transmitted optical communication power (P opt ) on the transmittance and received Q-factor of the link is also studied for light and dense fog densities.