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Centurion Harbor Surveillance Program for Homeland Security ApplicationsNorthrop Grumman’s FOAS technology

is a key element in the Centurion Port-

Harbor Anti-Terrorism/Force Protection

system which provides the operator with

a complete status of the harbor he

is monitoring.

This integrated sensor and display product

shows the harbor vicinity and potential

threats on a standard Navy display system

located at the test site. During a demon-

stration, divers with a battery-powered

underwater propulsion device were easily

detected attempting to penetrate the har-

bor. Surface craft traveling in the test area,

and entering the restricted Port of Huen-

eme, were also detected and tracked.

The proof-of-concept demonstration was

completed within three months of the

contract award by the U.S. Navy’s Mari-

time Surveillance Systems Program Offi ce,

utilizing passive fi ber-optic sonar arrays

and support equipment delivered by

Northrop Grumman’s Navigation Systems

Division, coupled with commercial-off-

the-shelf equipment provided by Northrop

Grumman’s Sperry Marine business unit in

Charlottesville, Virginia.

The equipment provided by Sperry Marine

included the marine radar, Automatic

Identifi cation System (AIS) shipboard iden-

tifi cation system and the digital electronic

charting system that provided the com-

mon integrated harbor picture.

The Northrop Grumman team completed

a threat analysis for the port and deter-

mined the most effective locations to place

the underwater arrays. The array installation

was performed with the assistance of the Na-

val Facilities Engineering Support Center and

the team’s ocean engineering subcontractor,

Sound and Sea Technology, Inc. of Edmonds,

Washington and Ventura, California.

Performance benefi ts of this technology

include unsurpassed detection, identifi ca-

tion and tracking capability for the harbor

defense applications. Since no electronic

components are in the water, the fi ber-optic

arrays provide a highly reliable solution that

also offers reduced acquisition and mainte-

nance costs. The arrays employ glass fi bers,

instead of older technology piezoelectric

hydrophones, to convert sound to modulated

light for effi cient transmission to shore.

Fiber-Optic Acoustic Sensors (FOAS)

Navigation Systems

24040 FOAS Overview/01-07/2000/Crawford

Northrop GrummanNavigation Systems Division21240 Burbank BoulevardWoodland Hills, California 91367 USA1-866-NGNAVSYS (646-2879)www.nsd.es.northropgrumman.com

Legacy Ceramic Array

Fiber-Optic Array

Hundreds of active electronic and optical components, joints,connectors and interfaces required for each channel

Less than 10 passive components and splices per channel

Acoustic Event ∆P

Optical Interrogation Analog Optical Output

λ0 λ +∆Φ0 ∆Φ/∆P

∆V∆PPower In

Multiplexand OpticalConversion

PreampSignalCond./Filters

A/DConv.

ClockSynchro

SensorNorthrop Grumman Corporation’s Navigation

Systems Division has applied its expertise in fi ber-

optic technology to develop a line of acoustic sensors it

calls Fiber-Optic Acoustic Sensors (FOAS). FOAS origi-

nated in 1981 as part of a major effort to develop both

fi ber-optic gyroscope and fi ber-optic hydrophone sensor

technologies. This effort, which has required investment

of over $140 million, has established Northrop Grumman

as the world’s leader in optical acoustic sensor technolo-

gy and exclusive manufacturer of Department of Defense

fi ber-optic acoustic sensor array systems.

FOAS Description and Capabilities

Northrop Grumman can produce fi ber-

optic acoustic sensor arrays for a variety of

applications. Northrop Grumman builds

three FOAS systems: hull arrays like the

Light Weight Wide Aperture Array

(LWWAA) currently on USS Virginia-Class

Submarines, towed arrays for submarine

and other applications, and fi xed bottom

arrays for deep ocean and shallow/littoral

water surveillance.

The arrays themselves comprise only pas-

sive fi ber-optic elements, and contain very

few parts and no electronics. One remote

transmit/receive station houses all the nec-

essary optoelectronics. The data are trans-

mitted on a few single mode fi bers, over

distances of more than 100 kilometers.

Over the past 15 years, Northrop Grum-

man and the U.S. Navy have made signifi -

cant strides in developing fi ber-optic sensor

technology for passive acoustic monitoring.

This work has focused on demonstrating

the advantages of fi ber-optics over conven-

tional piezoceramic sensor arrays.

One of the primary advantages of fi ber-

optic acoustic arrays is their simplicity.

Ceramic acoustic arrays require power,

complex electronics and signal processing

to be located close to the sensor to over-

come resistance losses.

Ceramic arrays also have numerous con-

nectors and mechanical joints that reduce

their reliability. The electronic processing

elements of a fi ber-optic array are located

in a dry or controlled environment on a

submarine or on shore. Their location al-

lows them to be accessed for maintenance

purposes and technological refresh, which

is not possible with legacy ceramic arrays.

Basic Principle of FOAS Operation

FOAS sensors use standard inter-

ferometer principles to detect acoustic

energy. Optic fi ber is wrapped tightly

around malleable plastic spools called

mandrels. As pressure from the acoustic

event moves across the sensor mandrel, it

changes shape causing the optical fi ber to

stretch or relax.

When light is projected through the

optical fi ber wrapped around the sensor

mandrel, the acoustic energy deforms the

mandrel and changes the distance the light

has to travel. This is compared to the dis-

tance light travels through the optical fi ber

on a reference mandrel. The optical phase

difference between the two, representing

the acoustic energy, can easily be mea-

sured and passed on to the signal process-

ing equipment.

Other advantages of fi ber-

optic arrays over convention-

al arrays include:

• Lower power requirements

• Increased reliability due to a

simplifi ed array design

• Reduced maintenance costs

• Lower cost to manufacture

• No underwater electrical compo-

nents or wires

• Light weight and small cable

diameter, which facilitate rapid de-

ployment and recovery of the array

• Immunity to electromagnetic

interference (EMI)

• Immunity to high radiation

• Diffi cult to detect since the fi ber-

optic sensor array is not operated

electrically and consists of only

non-metallic materials.

Light Weight Wide Aperture Array on Virginia Class SubmarinesThe Navy’s newest Virginia-class subma-

rines employ a Light Weight Wide Aperture

Array (LWWAA) on its hull for advanced

acoustic detection. The LWWAA system is

a set of large array panels that are mounted

on either side of the submarine, which

provide sonar sensor input to the subma-

rine’s combat system. Instead of traditional

ceramic hydrophone sensors, the

LWWAA uses FOAS technologies to con-

vert a target submarine’s acoustic energy in

the water into information that can be used

to identify and track it. Northrop Grumman

designed, developed and manufactures the

key optical sensing elements of this

FOAS array.

Towed ArraysNorthrop Grumman has designed and

developed high channel count fi ber optic

towed arrays for submarine applications.

The performance of these arrays has been

superior to equivalent ceramic arrays and

its ruggedness and reliability have been ex-

ceptional. It is expected that future towed

array systems will transition to fi ber-optic

technology to take advantage of the lower

cost, reliability and ruggedness.

Surveillance SystemsThe U.S. Navy and Northrop Grumman

continue to be actively involved in the de-

velopment of all fi ber-optic acoustic sensor

surveillance arrays for anti-submarine war-

fare passive sonar. They may be deployed

in all types of terrain and marine environ-

ments to accommodate such applications

as perimeter security, harbor monitoring,

and ground surveillance. Depending on

the application, these arrays may contain

optical geophones, fi ber-optic hydro-

phones, and/or fi ber-optic microphones.

The Centurion Harbor Surveillance pro-

gram demonstrates our FOAS capabilities

in this area.

Legacy Ceramic Array

Fiber-Optic Array

Hundreds of active electronic and optical components, joints,connectors and interfaces required for each channel

Less than 10 passive components and splices per channel

Acoustic Event ∆P

Optical Interrogation Analog Optical Output

λ0 λ +∆Φ0 ∆Φ/∆P

∆V∆PPower In

Multiplexand OpticalConversion

PreampSignalCond./Filters

A/DConv.

ClockSynchro

SensorNorthrop Grumman Corporation’s Navigation

Systems Division has applied its expertise in fi ber-

optic technology to develop a line of acoustic sensors it

calls Fiber-Optic Acoustic Sensors (FOAS). FOAS origi-

nated in 1981 as part of a major effort to develop both

fi ber-optic gyroscope and fi ber-optic hydrophone sensor

technologies. This effort, which has required investment

of over $140 million, has established Northrop Grumman

as the world’s leader in optical acoustic sensor technolo-

gy and exclusive manufacturer of Department of Defense

fi ber-optic acoustic sensor array systems.

FOAS Description and Capabilities

Northrop Grumman can produce fi ber-

optic acoustic sensor arrays for a variety of

applications. Northrop Grumman builds

three FOAS systems: hull arrays like the

Light Weight Wide Aperture Array

(LWWAA) currently on USS Virginia-Class

Submarines, towed arrays for submarine

and other applications, and fi xed bottom

arrays for deep ocean and shallow/littoral

water surveillance.

The arrays themselves comprise only pas-

sive fi ber-optic elements, and contain very

few parts and no electronics. One remote

transmit/receive station houses all the nec-

essary optoelectronics. The data are trans-

mitted on a few single mode fi bers, over

distances of more than 100 kilometers.

Over the past 15 years, Northrop Grum-

man and the U.S. Navy have made signifi -

cant strides in developing fi ber-optic sensor

technology for passive acoustic monitoring.

This work has focused on demonstrating

the advantages of fi ber-optics over conven-

tional piezoceramic sensor arrays.

One of the primary advantages of fi ber-

optic acoustic arrays is their simplicity.

Ceramic acoustic arrays require power,

complex electronics and signal processing

to be located close to the sensor to over-

come resistance losses.

Ceramic arrays also have numerous con-

nectors and mechanical joints that reduce

their reliability. The electronic processing

elements of a fi ber-optic array are located

in a dry or controlled environment on a

submarine or on shore. Their location al-

lows them to be accessed for maintenance

purposes and technological refresh, which

is not possible with legacy ceramic arrays.

Basic Principle of FOAS Operation

FOAS sensors use standard inter-

ferometer principles to detect acoustic

energy. Optic fi ber is wrapped tightly

around malleable plastic spools called

mandrels. As pressure from the acoustic

event moves across the sensor mandrel, it

changes shape causing the optical fi ber to

stretch or relax.

When light is projected through the

optical fi ber wrapped around the sensor

mandrel, the acoustic energy deforms the

mandrel and changes the distance the light

has to travel. This is compared to the dis-

tance light travels through the optical fi ber

on a reference mandrel. The optical phase

difference between the two, representing

the acoustic energy, can easily be mea-

sured and passed on to the signal process-

ing equipment.

Other advantages of fi ber-

optic arrays over convention-

al arrays include:

• Lower power requirements

• Increased reliability due to a

simplifi ed array design

• Reduced maintenance costs

• Lower cost to manufacture

• No underwater electrical compo-

nents or wires

• Light weight and small cable

diameter, which facilitate rapid de-

ployment and recovery of the array

• Immunity to electromagnetic

interference (EMI)

• Immunity to high radiation

• Diffi cult to detect since the fi ber-

optic sensor array is not operated

electrically and consists of only

non-metallic materials.

Light Weight Wide Aperture Array on Virginia Class SubmarinesThe Navy’s newest Virginia-class subma-

rines employ a Light Weight Wide Aperture

Array (LWWAA) on its hull for advanced

acoustic detection. The LWWAA system is

a set of large array panels that are mounted

on either side of the submarine, which

provide sonar sensor input to the subma-

rine’s combat system. Instead of traditional

ceramic hydrophone sensors, the

LWWAA uses FOAS technologies to con-

vert a target submarine’s acoustic energy in

the water into information that can be used

to identify and track it. Northrop Grumman

designed, developed and manufactures the

key optical sensing elements of this

FOAS array.

Towed ArraysNorthrop Grumman has designed and

developed high channel count fi ber optic

towed arrays for submarine applications.

The performance of these arrays has been

superior to equivalent ceramic arrays and

its ruggedness and reliability have been ex-

ceptional. It is expected that future towed

array systems will transition to fi ber-optic

technology to take advantage of the lower

cost, reliability and ruggedness.

Surveillance SystemsThe U.S. Navy and Northrop Grumman

continue to be actively involved in the de-

velopment of all fi ber-optic acoustic sensor

surveillance arrays for anti-submarine war-

fare passive sonar. They may be deployed

in all types of terrain and marine environ-

ments to accommodate such applications

as perimeter security, harbor monitoring,

and ground surveillance. Depending on

the application, these arrays may contain

optical geophones, fi ber-optic hydro-

phones, and/or fi ber-optic microphones.

The Centurion Harbor Surveillance pro-

gram demonstrates our FOAS capabilities

in this area.

Legacy Ceramic Array

Fiber-Optic Array

Hundreds of active electronic and optical components, joints,connectors and interfaces required for each channel

Less than 10 passive components and splices per channel

Acoustic Event ∆P

Optical Interrogation Analog Optical Output

λ0 λ +∆Φ0 ∆Φ/∆P

∆V∆PPower In

Multiplexand OpticalConversion

PreampSignalCond./Filters

A/DConv.

ClockSynchro

SensorNorthrop Grumman Corporation’s Navigation

Systems Division has applied its expertise in fi ber-

optic technology to develop a line of acoustic sensors it

calls Fiber-Optic Acoustic Sensors (FOAS). FOAS origi-

nated in 1981 as part of a major effort to develop both

fi ber-optic gyroscope and fi ber-optic hydrophone sensor

technologies. This effort, which has required investment

of over $140 million, has established Northrop Grumman

as the world’s leader in optical acoustic sensor technolo-

gy and exclusive manufacturer of Department of Defense

fi ber-optic acoustic sensor array systems.

FOAS Description and Capabilities

Northrop Grumman can produce fi ber-

optic acoustic sensor arrays for a variety of

applications. Northrop Grumman builds

three FOAS systems: hull arrays like the

Light Weight Wide Aperture Array

(LWWAA) currently on USS Virginia-Class

Submarines, towed arrays for submarine

and other applications, and fi xed bottom

arrays for deep ocean and shallow/littoral

water surveillance.

The arrays themselves comprise only pas-

sive fi ber-optic elements, and contain very

few parts and no electronics. One remote

transmit/receive station houses all the nec-

essary optoelectronics. The data are trans-

mitted on a few single mode fi bers, over

distances of more than 100 kilometers.

Over the past 15 years, Northrop Grum-

man and the U.S. Navy have made signifi -

cant strides in developing fi ber-optic sensor

technology for passive acoustic monitoring.

This work has focused on demonstrating

the advantages of fi ber-optics over conven-

tional piezoceramic sensor arrays.

One of the primary advantages of fi ber-

optic acoustic arrays is their simplicity.

Ceramic acoustic arrays require power,

complex electronics and signal processing

to be located close to the sensor to over-

come resistance losses.

Ceramic arrays also have numerous con-

nectors and mechanical joints that reduce

their reliability. The electronic processing

elements of a fi ber-optic array are located

in a dry or controlled environment on a

submarine or on shore. Their location al-

lows them to be accessed for maintenance

purposes and technological refresh, which

is not possible with legacy ceramic arrays.

Basic Principle of FOAS Operation

FOAS sensors use standard inter-

ferometer principles to detect acoustic

energy. Optic fi ber is wrapped tightly

around malleable plastic spools called

mandrels. As pressure from the acoustic

event moves across the sensor mandrel, it

changes shape causing the optical fi ber to

stretch or relax.

When light is projected through the

optical fi ber wrapped around the sensor

mandrel, the acoustic energy deforms the

mandrel and changes the distance the light

has to travel. This is compared to the dis-

tance light travels through the optical fi ber

on a reference mandrel. The optical phase

difference between the two, representing

the acoustic energy, can easily be mea-

sured and passed on to the signal process-

ing equipment.

Other advantages of fi ber-

optic arrays over convention-

al arrays include:

• Lower power requirements

• Increased reliability due to a

simplifi ed array design

• Reduced maintenance costs

• Lower cost to manufacture

• No underwater electrical compo-

nents or wires

• Light weight and small cable

diameter, which facilitate rapid de-

ployment and recovery of the array

• Immunity to electromagnetic

interference (EMI)

• Immunity to high radiation

• Diffi cult to detect since the fi ber-

optic sensor array is not operated

electrically and consists of only

non-metallic materials.

Light Weight Wide Aperture Array on Virginia Class SubmarinesThe Navy’s newest Virginia-class subma-

rines employ a Light Weight Wide Aperture

Array (LWWAA) on its hull for advanced

acoustic detection. The LWWAA system is

a set of large array panels that are mounted

on either side of the submarine, which

provide sonar sensor input to the subma-

rine’s combat system. Instead of traditional

ceramic hydrophone sensors, the

LWWAA uses FOAS technologies to con-

vert a target submarine’s acoustic energy in

the water into information that can be used

to identify and track it. Northrop Grumman

designed, developed and manufactures the

key optical sensing elements of this

FOAS array.

Towed ArraysNorthrop Grumman has designed and

developed high channel count fi ber optic

towed arrays for submarine applications.

The performance of these arrays has been

superior to equivalent ceramic arrays and

its ruggedness and reliability have been ex-

ceptional. It is expected that future towed

array systems will transition to fi ber-optic

technology to take advantage of the lower

cost, reliability and ruggedness.

Surveillance SystemsThe U.S. Navy and Northrop Grumman

continue to be actively involved in the de-

velopment of all fi ber-optic acoustic sensor

surveillance arrays for anti-submarine war-

fare passive sonar. They may be deployed

in all types of terrain and marine environ-

ments to accommodate such applications

as perimeter security, harbor monitoring,

and ground surveillance. Depending on

the application, these arrays may contain

optical geophones, fi ber-optic hydro-

phones, and/or fi ber-optic microphones.

The Centurion Harbor Surveillance pro-

gram demonstrates our FOAS capabilities

in this area.

���������������������������������������������������������������������

������������������������������������������������������������������������������������������������

���������������������������������������������������������������������������������

Centurion Harbor Surveillance Program for Homeland Security ApplicationsNorthrop Grumman’s FOAS technology

is a key element in the Centurion Port-

Harbor Anti-Terrorism/Force Protection

system which provides the operator with

a complete status of the harbor he

is monitoring.

This integrated sensor and display product

shows the harbor vicinity and potential

threats on a standard Navy display system

located at the test site. During a demon-

stration, divers with a battery-powered

underwater propulsion device were easily

detected attempting to penetrate the har-

bor. Surface craft traveling in the test area,

and entering the restricted Port of Huen-

eme, were also detected and tracked.

The proof-of-concept demonstration was

completed within three months of the

contract award by the U.S. Navy’s Mari-

time Surveillance Systems Program Offi ce,

utilizing passive fi ber-optic sonar arrays

and support equipment delivered by

Northrop Grumman’s Navigation Systems

Division, coupled with commercial-off-

the-shelf equipment provided by Northrop

Grumman’s Sperry Marine business unit in

Charlottesville, Virginia.

The equipment provided by Sperry Marine

included the marine radar, Automatic

Identifi cation System (AIS) shipboard iden-

tifi cation system and the digital electronic

charting system that provided the com-

mon integrated harbor picture.

The Northrop Grumman team completed

a threat analysis for the port and deter-

mined the most effective locations to place

the underwater arrays. The array installation

was performed with the assistance of the Na-

val Facilities Engineering Support Center and

the team’s ocean engineering subcontractor,

Sound and Sea Technology, Inc. of Edmonds,

Washington and Ventura, California.

Performance benefi ts of this technology

include unsurpassed detection, identifi ca-

tion and tracking capability for the harbor

defense applications. Since no electronic

components are in the water, the fi ber-optic

arrays provide a highly reliable solution that

also offers reduced acquisition and mainte-

nance costs. The arrays employ glass fi bers,

instead of older technology piezoelectric

hydrophones, to convert sound to modulated

light for effi cient transmission to shore.

Fiber-Optic Acoustic Sensors (FOAS)

Navigation Systems

24040 FOAS Overview/01-07/2000/Crawford

Northrop GrummanNavigation Systems Division21240 Burbank BoulevardWoodland Hills, California 91367 USA1-866-NGNAVSYS (646-2879)www.nsd.es.northropgrumman.com

���������������������������������������������������������������������

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���������������������������������������������������������������������������������

Centurion Harbor Surveillance Program for Homeland Security ApplicationsNorthrop Grumman’s FOAS technology

is a key element in the Centurion Port-

Harbor Anti-Terrorism/Force Protection

system which provides the operator with

a complete status of the harbor he

is monitoring.

This integrated sensor and display product

shows the harbor vicinity and potential

threats on a standard Navy display system

located at the test site. During a demon-

stration, divers with a battery-powered

underwater propulsion device were easily

detected attempting to penetrate the har-

bor. Surface craft traveling in the test area,

and entering the restricted Port of Huen-

eme, were also detected and tracked.

The proof-of-concept demonstration was

completed within three months of the

contract award by the U.S. Navy’s Mari-

time Surveillance Systems Program Offi ce,

utilizing passive fi ber-optic sonar arrays

and support equipment delivered by

Northrop Grumman’s Navigation Systems

Division, coupled with commercial-off-

the-shelf equipment provided by Northrop

Grumman’s Sperry Marine business unit in

Charlottesville, Virginia.

The equipment provided by Sperry Marine

included the marine radar, Automatic

Identifi cation System (AIS) shipboard iden-

tifi cation system and the digital electronic

charting system that provided the com-

mon integrated harbor picture.

The Northrop Grumman team completed

a threat analysis for the port and deter-

mined the most effective locations to place

the underwater arrays. The array installation

was performed with the assistance of the Na-

val Facilities Engineering Support Center and

the team’s ocean engineering subcontractor,

Sound and Sea Technology, Inc. of Edmonds,

Washington and Ventura, California.

Performance benefi ts of this technology

include unsurpassed detection, identifi ca-

tion and tracking capability for the harbor

defense applications. Since no electronic

components are in the water, the fi ber-optic

arrays provide a highly reliable solution that

also offers reduced acquisition and mainte-

nance costs. The arrays employ glass fi bers,

instead of older technology piezoelectric

hydrophones, to convert sound to modulated

light for effi cient transmission to shore.

Fiber-Optic Acoustic Sensors (FOAS)

Navigation Systems

24040 FOAS Overview/01-07/2000/Crawford

Northrop GrummanNavigation Systems Division21240 Burbank BoulevardWoodland Hills, California 91367 USA1-866-NGNAVSYS (646-2879)www.nsd.es.northropgrumman.com