Post on 26-May-2015
description
PRESENTED BY-
CHANDANI
AMANDEEP KAUR
RAJAN KUMAR MISHRA
FREE SPACE OPTICS
COMMUNICATION
2
LAYOUTS
HISTORY OF FSO INTRODUCTION ARCHITECTURE WORKING OF FSO LINK & SYSTEM DESIGN LAST MILE BOTTLENECK SECURITY ISSUE CHALLENGES ADVANTAGE & DISADVANTAGE APPLICATION MANUFACTURES CONCLUSION REFERENCES
3
HISTORY OF FSO
Greek’s used fire for messaging.
On Feb 19,1880 Alexander Graham Bell and his assistant Charles Sumner Tainter created “Photo Phone(Radio Phone)” was practically first used in military comm. system.
In 2008 the company MRV Comm. has introduced the free space optic based Terescope TS-10GE system with data rate 10Gbps on a distance till 350m.
4
Requirements of a good Transmission System: High Bandwidth High Bit Rate Low SNR Power efficient Provide Data Security. Low cost Easy to install and maintain.
5
INTRODUCTION Free Space Optics communications, also
called Free Space Photonics (FSP) or Optical Wireless, refers to the transmission of visible and infrared (IR) beams through the atmosphere to obtain optical communications.
FSO is a line-of-sight technology which uses LASERS and Photo detectors to provide optical connections between two points—without the fiber.
Free space optical communication is an effective means of communication at high bit rates over short distances.
Free Space Optics uses lasers and LED to transmit data, but instead of enclosing the data stream in a glass fiber, it is transmitted through the air.
It is a device that allows for the transmission of sound on a beam of light
6
FSO Major Sub System
7
ARCHITECTURE
8
WORKING
The electrical signal is converted to optical power and
transmitted through the air.
After undergoing the influences of the time-dispersive
channel and ambient light, the optical signal is directly
translated into a photocurrent at the detector.
The electrical SNR in optical links depends on the
square of the optical power, which has a deep impact on
both design and performance of OW systems.
9
Why Free Space Optics?
How FSO Works
1 Network traffic converted into pulses of invisible light representing 1’s and 0’s
2 Transmitter projects the carefully aimed light pulses into the air
5 Reverse direction data transported the same way.
• Full duplex
3 A receiver at the other end of the link collects the light using lenses and/or mirrors
4Received signal converted back into fiber or copper and connected to the networkAnything that can be done in
fiber can be done with FSO
10
SYSTEM DESIGN
Line of sight operation
Spectral AllocationFSO link operationCoverage area Installation Network
topologies
11
AT TRANSMITTER:
One or more laser diodes (LD) or
light emitting diodes (LED) are used
(mainly semiconductor lasers). The
choice between LED and LD is
determined by standard factors that
influence price and performance as
known from traditional optical
communications.
12750 nm 1550 nm
Channel model
13
AT RECIEVER:An optical concentrator ( collect
and concentrate incoming radiation) and an
optical filter (to reject ambient light), a
photo detector (PD, to convert radiation/
optical power into a photocurrent), and an
electrical front-end
14
LINK DESIGNThere are two basic link designs:
Directed line-of-sight (LOS) :
The beam of a directed link travels from a narrow-beam Tx
to a narrow field-of-view (FOV) receiver(Rx) via the LOS.
Diffuse link:
Communication between a wide-beam Tx and a wide FOV
Rx relies on numerous signal reflections off the surfaces in
the room, instead of a LOS.
15
Free Space Optic Link Equation:
HerePreceived = Received PowerPtransmit = Tranmitted PowerAreceiver = Area of the Receiver
Div = Divergence of the beam (in rad)Range = Link length
16
LAST MILE BOTTLENECKS
17
SECURITY ISSUE
The laser beams generated by FSO system are narrow and invisible making them harder to find and even harder to intercept and crack.
In FSO N-slit interferometric pattern is used which prevent the signal from collapsing therefore received data is more secured.
It improved electromagnetic interference.
18
Signal Propagation Impediments:
ABSORPTION SCATTERING FOG SCINTILLATION SOLAR INTERFERENCE DISPERSION BUILDING MOTION SAFETY PHYSICAL OBSTRUCTRIONS
Challenges
Environmental factorsSunlight
Building Motion
Alignment
WindowAttenuation
Fog
Each of these factors can “attenuate” (reduce) the signal. However, there are ways to mitigate each environmental factor.
Scintillation
RangeObstructions
Low Clouds
20
ADVANTAGES
Easy to install & installation cost is low.
License free long range operation.
Full duplex operation. Low bit error rate. Highly secure
transmission possible. Possible to mount
inside the building
21
DISADVANTAGES
Beam dispersion Atmospheric absorption Rain Fog Snow Pollution / smog Limited bandwidth Solar interfacing
22
APPLICATIONS Used where fiber communication is not possible. LAN-to-LAN connections on campuses at Fast
Ethernet or Gigabit Ethernet speeds. LAN-to-LAN connections in a city, a metropolitan
area network. As an alternative or upgrade add-on
to existing wireless technologies For communications between
spacecraft .
23
Manufacturers/ Players in the Field of FSO:
LightPointe: A San Diego based company which received contributions from Cisco Systems and Corning to the tune of $33 million. It has raised a total of $51.5 million.
AirFiber: Another San Diego based company which has received contributions from Nortel Networks to the tune of $50 million. It has raised a total of $92.5 million.
Terabeam: A Kirkland, WA based company has received funding from Luscent technologies to the tune of $450 million and has raised $585 million to date.
24
Conclusion
FSO networks can be rapidly deployed to provide immediate service to the customers. Some believe that it may be the unlimited bandwidth solution for the metro urban core of downtown building-to-building communication, as well as the optimal technology for home-to-home and office-to-office connectivity. FSO adds the wireless feature to the OFC and thus provides the high bandwidth requirements.
25
REFERENCES
http://www.ieee.org
http://www.spacephotonics.com
http://www.lightpointe.com
http://www.freespaceoptics.org
26
Thank you &Queries