03-12-2012, 05:01 PM
Free Space Optical Communication(FSOC) and Its Application
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Introduction
Free-space optical communication (FSO) is an optical communication technology .
FSO can transmit data, voice or video at speeds capable of reaching 2.5 gbps.
FSO units consist of an optical transceiver with a laser (transmitter) and a photo detector (receiver) to provide full duplex capability .
Types of Optical Communication
Optical communication is broadly divided into two categories as follows
Optical Fiber Communication (OFC)
Free Space/Wireless Optical Communication (FSOC/WOC)
History Of Optical Communication
The ancient Greeks used light in the battle to send signal
In 1880 Alexander Graham Bell created the ‘Photo-phone’, allowed for the transmission of sound on a beam of light.
German scientist Carl Zeist Jena developed the Lichtsprechgerät 80 (light speaking device) that the German army used in their World War II as anti-aircraft defence units.
The invention of lasers in the 1960s revolutionized free space optics for which Military organizations were particularly interested and boosted their development.
Optical Fiber Communication(OFC)
Uses optical fiber to transmit information by sending pulses of light
The light forms an electromagnetic carrier wave that is modulated to carry information.
Since light is the carrier so fastest of all other communication techniques
A Few Points about Optical Fiber (OF)
An Indian physicist Narinder Singh Kapani is said to be the ‘Father of Optical Fiber’.
An optical fiber is a flexible, transparent fiber made of glass (silica) or plastic, slightly thicker than a human hair.
It functions as a waveguide or light pipe to transmit light between the two ends of the fiber.
It has four parts- core, cladding buffer and jacket
The phenomenon of ‘Total Internal Reflection’(TIR) is obeyed inside the fiber to keep light propagating through it.
Signal Propagation Impediments
Fog: The primary way to counter fog when deploying FSO is through a network design that shortens FSO link distances.
Absorption: Absorption occurs when suspended water molecules in the terrestrial atmosphere exist. This causes a decrease in the power density (attenuation) of the FSO beam.
Scattering: Scattering is caused when the wavelength collides with the scatterer. The physical size of the scatterer with respect to wavelength determines the type of scattering- Rayleigh or Mie
Physical obstructions: Flying birds can temporarily block a single beam.
Building sway/seismic activity: The movement of buildings can upset receiver and transmitter alignment.
Safety: To those unfamiliar with FSO, safety is often a concern because the technology uses lasers for transmission.
Scintillation: Heated air rising from the earth or man-made devices creates temperature variations among different air pockets. This can cause fluctuations in signal amplitude which leads to image fluctuations at the FSO receiver end.
Conclusion
FSOC is touted to replace RF communication in every field of science.
With its immense BW and speed, it can achieve a data rate that is never possible for copper wire architecture.
Although it has got some negativities but it is still in its infancy .
Its advantages will surely be made use of in communication replacing OFC and Copper wired communication
[attachment=42288]
Introduction
Free-space optical communication (FSO) is an optical communication technology .
FSO can transmit data, voice or video at speeds capable of reaching 2.5 gbps.
FSO units consist of an optical transceiver with a laser (transmitter) and a photo detector (receiver) to provide full duplex capability .
Types of Optical Communication
Optical communication is broadly divided into two categories as follows
Optical Fiber Communication (OFC)
Free Space/Wireless Optical Communication (FSOC/WOC)
History Of Optical Communication
The ancient Greeks used light in the battle to send signal
In 1880 Alexander Graham Bell created the ‘Photo-phone’, allowed for the transmission of sound on a beam of light.
German scientist Carl Zeist Jena developed the Lichtsprechgerät 80 (light speaking device) that the German army used in their World War II as anti-aircraft defence units.
The invention of lasers in the 1960s revolutionized free space optics for which Military organizations were particularly interested and boosted their development.
Optical Fiber Communication(OFC)
Uses optical fiber to transmit information by sending pulses of light
The light forms an electromagnetic carrier wave that is modulated to carry information.
Since light is the carrier so fastest of all other communication techniques
A Few Points about Optical Fiber (OF)
An Indian physicist Narinder Singh Kapani is said to be the ‘Father of Optical Fiber’.
An optical fiber is a flexible, transparent fiber made of glass (silica) or plastic, slightly thicker than a human hair.
It functions as a waveguide or light pipe to transmit light between the two ends of the fiber.
It has four parts- core, cladding buffer and jacket
The phenomenon of ‘Total Internal Reflection’(TIR) is obeyed inside the fiber to keep light propagating through it.
Signal Propagation Impediments
Fog: The primary way to counter fog when deploying FSO is through a network design that shortens FSO link distances.
Absorption: Absorption occurs when suspended water molecules in the terrestrial atmosphere exist. This causes a decrease in the power density (attenuation) of the FSO beam.
Scattering: Scattering is caused when the wavelength collides with the scatterer. The physical size of the scatterer with respect to wavelength determines the type of scattering- Rayleigh or Mie
Physical obstructions: Flying birds can temporarily block a single beam.
Building sway/seismic activity: The movement of buildings can upset receiver and transmitter alignment.
Safety: To those unfamiliar with FSO, safety is often a concern because the technology uses lasers for transmission.
Scintillation: Heated air rising from the earth or man-made devices creates temperature variations among different air pockets. This can cause fluctuations in signal amplitude which leads to image fluctuations at the FSO receiver end.
Conclusion
FSOC is touted to replace RF communication in every field of science.
With its immense BW and speed, it can achieve a data rate that is never possible for copper wire architecture.
Although it has got some negativities but it is still in its infancy .
Its advantages will surely be made use of in communication replacing OFC and Copper wired communication