Well, I try and keep up on what's going on, and I must say that this completely caught me unawares. I found the original through a blog I visit entitled Molten Eagle. It written by a submariner and has a LOT of interesting stuff. Anyway, the original article appeared in Military and Aerospace Electronics in February, 2002. Because it's relatively short, I'm posting it all here. I am VERY interested in learning more about this system, and would like to hear from anyone with information they are willing to share.
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By John Keller
WOODLAND
HILLS, Calif. — Sonar experts from the Northrop Grumman Navigation
Systems Division in Woodland Hills, Calif., envision a vast ocean-floor
optical sensor array that can detect and track some of the world's
quietest submarines through minute phase shifts of light.
This array, which U.S. Navy leaders call the All Optical Underwater
Segment — or AO-UWS — is to be deployed in strategic ocean areas that
either funnel heavy submarine traffic, or where pinpointing hostile
submarines is crucial.
The
AO-UWS could go on line as early as 2004, says Jim Andersen, director
of business development for fiber optic acoustic systems at Northrop
Grumman Navigation Systems.
Northrop
Grumman engineers are designing the AO-UWS optical sensor array under
terms of an $8.9 million contract from the U.S. Space and Naval Warfare
Systems Command (SPAWAR) in San Diego. The 24-month development program
will culminate in an at-sea demonstration of the system sometime in
2003.
Among
the chief advantages of underwater optical sensors are sensitivity and
reliability, Andersen says. Optical sensors are to augment or replace
existing underwater arrays of electronic hydrophones that are part of
the U.S. Navy's Integrated Undersea Surveillance System — better known
as the IUSS.
"This
system is for deep water, so you could deploy it anywhere," Andersen
says. "It will be large fields of sensors — hundreds to thousands of
sensors — that are used for ASW- [anti-submarine warfare] type
detection."
The
sensor array and signal-transmission media will be all-optical
components — manufactured from plastic or silica, which is not
susceptible to the corrosive influences of saltwater, Andersen says.
Electronic components, on the other hand, can suffer corrosion or
short-circuits in seawater, which present the Navy with a persistent
maintenance headache.
"The
advantage is there is no electronics in the water, or on the 'wet end',
so the stuff we put in the water is very reliable" Andersen explains.
"All the electronics is on shore or on a ship, which can be mounted in
COTS [commercial off-the-shelf] versions; you don't have to package
electronics for the water, and you can rely much more on standard COTS
electronics."
The
AO-UWS sensor array detects phase shifts in light waves caused by the
sounds of submarines. "We put a carrier frequency on the light beam,
and at the sensor the acoustic pressure signal will shift the phase of
the light," Andersen says. "It is these phase shifts that we pick up."
The
AO-UWS works by connecting arrays of optical sensors with optical
fiber. These interconnected arrays, in turn, connect via optical fiber
with signal-processing gear on shore, aboard ships, or inside
submarines.
"Once
we convert the optical signal back into a voltage signal, we format it
to whatever someone might want, such as fast Ethernet," Andersen says.
"We rely on the signal-processing people to process it however they
want. We just give it to them in the right format for the processing."
Two
subcontractors are working with Northrop Grumman to develop the AO-UWS
— MariPro Inc. of Goleta, Calif., which is concentrating on mechanical
wet-end junctions, terminations, and packaging; and Digital System
Resources (DSR) Inc. of Fairfax, Va., which concentrates on interfacing
to existing Navy sonar processing systems.
The
AO-UWS is to become part of the Navy's Integrated Undersea Surveillance
System, which includes the Sound Surveillance System (SOSUS), Fixed
Surveillance System (FSS), the Fixed Distributed System (FDS), the
Surveillance Towed Array Sensor System (SURTASS), and the Advanced
Deployable System (ADS).
Northrop
Grumman sonar experts envision the AO-UWS as a complement or
replacement for the Fixed Distributed System, Andersen says. The FDS is
a fork-shaped array of ocean-floor sensors that not only detect the
sounds of submarines, but also help analysts use triangulation to
gather range and bearing information.
Northrop
Grumman is also using optical sonar sensors on submarines such as the
future Virginia-class new attack submarine to enhance
submarine-detection capabilities, and also to reduce maintenance tasks.
With
optical sensors on submarines, "the beauty is the previous system had
electronics external to the pressure hull," Andersen explains. "It is
difficult to maintain them, even in port. We had to dry-dock them. Now
we have optical fiber outboard and the electronic maintenance issues
involve simply changing out a printed circuit card. They can do that
even underway."
Military & Aerospace Electronics February, 2002
Author(s) :
John Keller
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