Aerospace & Defense Technology - August 2024 - 26

RF & Microwave Technology
Space Lasers:
Aiming Towards Next Leap in
Global Communications
S
pace lasers are transforming the world. Not the far-off
future of science fiction, but the universe of how data
and communications flow today - everywhere from
deep space missions to countless applications here on
earth, including consumer internet services, military operations,
and banking transactions.
Lasers can transmit vast amounts of data over great distances
at the speed of light, 100 times faster than previously possible
in space. The narrowness of the light beams makes laser communication
remarkably efficient. The highly focused light is
aimed at the receiver, resulting in minimal beam divergence
and signal loss and allowing for reduced power consumption.
Indeed, this narrowness of the laser beam also presents
daunting technological challenges. In space laser communications,
impeccable precision is needed to align transmitters and
receivers across vast distances as the terminals move at varying
speeds and directions - a level of accuracy comparable to hitting
a three-point basketball shot from 100 miles away.
Engineers have addressed these challenges by developing
fast steering mirrors (FSM) controlled with extremely sensitive
sensors. These systems keep the beam precisely on target for
satellite-to-satellite and ground-to-satellite links and deepspace
communication, facilitating accelerated growth in the
flow of data around the globe.
The Galactic Network
These capabilities - laser communications
with FSM tracking - are
bringing us closer to what
might be called the
" Galactic Internet. "
That was the imaginative term coined in the early 1960s by J.
C. R. Licklider, the first director of the Information Processing
Techniques Office (IPTO) at the Pentagon's ARPA, to describe the
possibility of a digital " network " open to all that would serve as
" the main and essential medium of informational interaction
for governments, institutions, corporations, and individuals. "
ARPANET became the first wide-area packet-switched network
with distributed control and proved instrumental in
shaping modern computer networking and the internet.
Copper Couldn't Satisfy the Insatiable Demand for
Bandwidth
In the early days of the internet, most data was transmitted
over copper cables, taking advantage of ubiquitous telephone
networks. However, electrical transmission over copper suffers
from signal attenuation due to resistance in the conductor and
dielectric losses.
As the internet evolved from text-based emails to images,
videos, and games, the standard 56.6-baud dial-up modems
became obsolete, and internet service providers (ISPs) and
backbone networks needed new transmission methods to keep
up with the tremendous surge in data traffic.
26
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Aerospace & Defense Technology - August 2024

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