Understanding Optical Communications



Introduction

The use of light to send messages is not new. Fires were used for signaling in
biblical times, smoke signals have been used for thousands of years and flashing
lights have been used to communicate between warships at sea since the days of
Lord Nelson.
The idea of using glass fibre to carry an optical communications signal originated
with Alexander Graham Bell. However this idea had to wait some 80 years for
better glasses and low-cost electronics for ....etc

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Abstract—Given a data point set , a query point set , and an integer , the Group Nearest Group (GNG) query finds a subset ( ) of points from such that the total distance from all points in to the nearest point in is not greater than any other subset ( ) of points in . GNG query is a partition-based clustering problem which can be found in many real applications and is NP-hard. In this paper, Exhaustive Hierarchical Combination (EHC) algorithm and Subset Hierarchial Refinement (SHR) algorithm are developed for GNG query pr ....etc

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Optical Communications in Space

In summer 1977, ESA placed the first technological study contract in the domain of intersatellite optical links. Now, twenty years later, a major milestone has been reached with the SILEX laser terminals having been flight tested for integration with their host spacecraft. At the same time, ESA is preparing itself for a new challenge: the potential massive use of optical cross links in satellite constellations for mobile communications and global multimedia services. This is an opportune moment to look back at ....etc

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In summer 1977, ESA placed the first technological study contract in the domain of intersatellite optical links. Now, twenty years later, a major milestone has been reached with the SILEX laser terminals having been flight tested for integration with their host spacecraft. At the same time, ESA is preparing itself for a new challenge: the potential massive use of optical cross links in satellite constellations for mobile communications and global multimedia services. This is an opportune moment to look back at the past twenty years of ESA effor ....etc

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The communication needs of Earth observation satellites is steadily increasing. Within a few
years, the data rate of such satellites will exceed 1 Gbps, the angular resolution of sensors will be
less than 1 μrad, and the memory size of onboard data recorders will be beyond 1 Tbytes.
Compared to radio frequency links, optical communications in space offer various advantages
such as smaller and lighter equipment, higher data rates, limited risk of interference with other
communications systems, and the effective use of freque ....etc

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In summer 1977, ESA placed the first technological study contract in the domain of intersatellite optical links. Now, twenty years later, a major milestone has been reached with the SILEX laser terminals having been flight tested for integration with their host spacecraft. At the same time, ESA is preparing itself for a new challenge: the potential massive use of optical cross links in satellite constellations for mobile communications and global multimedia services. This is an opportune moment to look back at the past twenty years of ESA effor ....etc

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SATELLITE OPTICAL COMMUNICATIONS
Presented By;
P.Gangadhar Reddy
B.Vamsi Krishna
Regno: 04A41A0425
Regno: 04A41A0481


ABSTRACT
Any Communication system needs a medium to operate. Satellite communication and optical communication are two different methods of communication. Satellite communication uses a satellite as a repeater between two points that exchange information, here medium is air and information is passed as electromagnetic waves. Satellite Communi ....etc

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http://freespaceopticsfreespaceoptics/images/flightstrata_photo.jpg
Free space optical communications is a line-of-sight (LOS) technology that transmits a modulated beam of visible or infrared light through the atmosphere for broadband communications. In a manner similar to fiber optical communications, free space optics uses a light emitting diode (LED) or laser (light amplification by stimulated emission of radiation) point source for data transmission. However, in free space optics, an energy beam is collimated and transmitted t ....etc

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free download of optical communication by bakshi ....etc

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