Free-Space Optical Communications Technologies

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23 Νοε 2013 (πριν από 3 χρόνια και 6 μήνες)

61 εμφανίσεις

Free
-
Space Optical
Communications
Technologies

Anatoly
Efimov

Materials Physics and Applications Division,
Center for Integrated Nanotechnologies, MPA
-
CINT, Los Alamos National
Laboratory

Funding:

LANL
-

LDRD

Background

Just like optical fiber telecom, but through atmosphere or free space

Advantages:


No fiber laying costs


No license


High data rates compared to RF


Smaller, lighter compared to RF


More efficient compared to RF


High security


Quick deployment

Applications:


Urban/metro networks


Moving platforms: ships,
planes, tanks, satellites,
planets


Emergency response,
disaster recovery


News crews

Disadvantages:


Technically challenging at
Gbps


Weather


Atmospheric turbulence



Customer point of view



Increasing bandwidth pressure on wireless communication systems



All the problems with RF: Allocation, License, Cost, Security, Power, Efficiency, Size



Existing FSO systems are stuck at ~1
Gbps

and ~2 km at BEST (~$100K per link)



Fundamental level



weather,



line of sight req.,



PAT req.,



diffraction loss



ambient bkg.,



turbulence

FSO: Problem Overview



Simple (cheap, slow) systems: single LD or LED in
Tx

and PIN or APD in Rx



Hybrid systems: Optics + RF backup



Multibeam

Tx
: Based on
Korevaar’s

patent to
AstroTerra
, sold to MRV for $100M



Multibeam

Tx

and
Multireceiver

Rx: mostly R&D at MIT Lincoln Labs



Adaptive optics: still in R&D stage, very expensive and complicated.



LANL R&D



Partially coherent beam



Wavelength diversity

FSO: Current state of the art

FSO: Partially Coherent Beam

Laser

PCB generator


Tx

system


Rx system: Standard

Det

Suitable for
Gbps

data rates

Preliminary work at LANL



PCB generation suitable for
Gbps

data rates



Laboratory experiments involving simulated atmospheric turbulence

Air in

Air out

Light in

Light out

Preliminary work at LANL

Using properly generated PCB we reduce the signal fluctuations by a factor of 10

0
5
10
15
20
25
0
1
2
3
4


Scintillation Index
Path Length through TC2 (m)
Coherent Beam
PCB, MMF50
PCB MMF100
Coherent

PCB1

PCB2

10
-
times scintillation index reduction using PCB2



Note that BER depends exponentially on
scintillation index, so this improvement is, in fact
huge!

Preliminary work at LANL

Eye diagrams

Standard laser

PCB

Work in progress at LANL

Open
-
air experiment for evaluation of LANL technologies and side
-
by
-
side comparison
with the state of the art

Conclusion: Our message



LANL has technologies for advancement of FSO
comm
: improved range, low cost,
easy upgrade for existing cheap systems



Our goal is commercialization with a partner, capable and willing to support the
ongoing R&D



Contact: Mike Ericson (505)667
-
8087 at LANL TT division