**2.7 State of the art of FOG**

*Gyroscopes - Principles and Applications*

by measuring the beat frequency, Dn.

*The principle diagram of stimulated Brillouin FOG.*

shock resistance and acceleration resistance.

the optical fiber coil.

**Figure 5.**

**2.5 Characteristics of FOG**

effectively overcome.

a long service life.

neously in theory.

6.It has a wide dynamic range.

interface.

in the optical fiber. The existence of this moving acoustic wave leads to the generation of stimulated Brillouin scattering (SBS). When two pumped beams (P1 and P2) are incident into the ring resonator in the opposite direction at the same time, two Brillouin beams (B1 and B2) opposite to the pumped beams will be generated. If the ring resonator is stationary, the two Brillouin beams are proportional to the frequency difference, Dn. Two Brillouin beams are photosynthesized and beat frequency is generated. The rotation rate of the optical fiber resonator can be obtained

The rotation angular velocity of the optical fiber coil is linearly related to the fre-

is the wavelength of the pumped light, L is the length of the optical fiber coil, *n* is the refractive index of the optical fiber coil, and the area *S* is the area surrounded by

1.All solid-state integration, the instrument is firm and stable, and has strong

3.Without mechanical moving parts, there is no wear and tear problem, so it has

4.The propagation time of coherent beams is very short and can start instanta-

5.It is easy to adopt integrated optical technology. The signal is stable and reliable. It can be output digitally and connected directly with the computer

7.It has simple structure, low price, small volume, and light weight [15].

2.The optical path is increased by the optical fiber ring, and the detection sensitivity and resolution are increased by several orders of magnitude compared with the laser gyroscope. Thus, the locking problem of the gyroscope is

4*S* <sup>λ</sup> · *nL*, where <sup>λ</sup>

quency difference of the output two Brillouin beams. The ratio factor is \_

**30**

FOG has different development and research status in different countries and has its own characteristics. The United States, Japan, France, Germany, Britain, and China are the main developing countries of FOG. Europe and the United States have obvious advantages in the research and development of high-precision FOG, while Japan pays more attention to the commercial application of low-precision FOG [13]. China and other countries also attach great importance to the research and promotion of FOG.

The United States is a pioneer in developing and applying FOG. Its contractors, universities, and government agencies are developing key technologies, such as Litton, Honeywell, KVH, Norhrop Grumman, and Draper Laboratory. These companies are mainly engaged in the research and development of high-precision FOG [23], providing services for the U.S. military and aerospace departments. They have also done very well in the development and production of FOG. At present, many types of FOG have been put into use in the United States.

Japan is also a big country in the research and production of FOG. The research institutes include the cutting-edge technology laboratory of Tokyo University, Hitachi Corporation, Mitsubishi Corporation [13], Japan Aerospace Electronics Company (JAE), Mitsubishi Precision Instrument, and so on. These companies


### **Table 3.**

*The key technological breakthroughs of FOG.*


**33**

measurement.

*On the Development and Application of FOG DOI: http://dx.doi.org/10.5772/intechopen.88542*

**3. Conclusion and expectation**

ization, high reliability, and long life.

tracking is less than 0.001°/h [30].

attach great importance to the practicality of FOG. They have mass-produced a variety of levels of FOG, especially those of medium and low precision. They are in the forefront of the world in practicality and can be applied to environmental

The research and development of FOG in Western European countries mainly focus on France, Italy, and Russia. These countries attach great importance to the development of military applications of FOG. These countries are mainly committed to the development of low performance FOG equipment with drift rate greater than 1 (°)/h, Navy and air force. The first generation of FOG has been put into production. For example, PHINS series FOG, which is produced by IxSea Company in France, has been applied to inertial navigation and deep-water operation. Civitanavi Systems, Italy, based on proprietary FOG technology, developed a FOG

FOG has different research and application in different countries. From **Table 4**,

After more than 30 years on research and exploration, the technology of FOG has achieved a high level. While guaranteeing the accuracy and meeting the current requirements, FOG is gradually developing in the direction of low cost, miniatur-

FOG has been mainly used in astronautics, including spacecraft, satellite, aircraft, etc., and it is also widely used in civil fields such as ship, automobile navigation, mine, and so on. Based on different zero bias stability, their applications are different. If the bias stability is greater than 10°/h, it can be employed in land vehicle navigation, robot attitude control, and camera or antenna stabilization device. And when the bias stability is small ranging from 0.001 to 0.01°/h, FOG can be used in aerospace inertial navigation system and navigation. Whereas, in precision spacecraft applications, the zero bias stability required for precise aiming and

FOG is a type of angular rate measurement instrument based on Sagnac effect. It has advantages of no moving parts and wearing parts, small size, light weight, large dynamic range, fast start-up, long life, low cost, impact-resistant structure, flexible design and simple production process, etc. [29, 31]. It is broadly used in inertial navigation systems such as aviation, navigation, and aerospace, and is not in the direction of high precision. Continuous development [29, 32] with the development of modern microelectronics technology, optoelectronics technology, and signal processing technology, FOG will continue to mature; its application will continue to expand. In the future, there will be a greater stage in the field of inertial

protection, vehicle navigation, industrial control, and so on.

[24] for attitude stabilization and navigation of satellite launchers.

we can see the application of FOG in different companies in the world.

#### **Table 4.**

*The application of FOG in the world.*

#### *On the Development and Application of FOG DOI: http://dx.doi.org/10.5772/intechopen.88542*

*Gyroscopes - Principles and Applications*

America Litton Industries

America Honeywell

America Northrop

**Country Company Main** 

Inc.

International Inc.

Grumman

Japan Hitachi, Ltd. Low and

France EuroFOG Serialization

China Beihang

China China Aerospace

*The application of FOG in the world.*

University

Times Electronics Co. Ltd.

**performance: Zero bias stability**

medium precision civil products of 10°/h

Russia Fizoptika 0.05°/h Its FOG has been commercialized.

from 10°/h to 0.01°/h

France IXSea 0.003°/h With a number of key patents of

Germany LITEF <0.01°/h Product applications cover space,

0.008°/h The SCIT experimental inertial

0.00023°/h It studies high-performance

<0.005°/h Its optical fiber technology has

device was developed in 1988. Then the CIGIF demonstration system flight test device, inertial measurement system and GPS/INS integrated navigation system are developed

interferometric FOG, whose products are widely used in satellite, rocket, aircraft and other aerospace fields

matured in the field of low and medium precision, and has been commercialized. Its main customers are some major airlines in the United States. Its products can be used in land, sea and air fields

Its optical fiber technology has matured in the field of low and medium precision, and has been commercialized. Its main customers are some major airlines in the United States. Its products can be used in land, sea and air fields

The product models are VG949, VG941B, etc.

Tri-axis scheme is adopted below 0.1°/h, and single-axis scheme is adopted at 0.01°/h

FOG, its application fields include offshore, underwater and space applications

air, land and water, as well as military and civilian applications. After 2003, integrated navigation system will be provided to provide position, course and attitude information for military reconnaissance vehicles

of FOG

of aeronautics and astronautics

0.005°/h It has a complete production line

0.01°/h Its product mainly used in the field

**Application Reference**

[25]

[26–28]

[26]

[29]

[30]

[26, 30]

[26]

[26]

[30]

[30]

**32**

**Table 4.**

attach great importance to the practicality of FOG. They have mass-produced a variety of levels of FOG, especially those of medium and low precision. They are in the forefront of the world in practicality and can be applied to environmental protection, vehicle navigation, industrial control, and so on.

The research and development of FOG in Western European countries mainly focus on France, Italy, and Russia. These countries attach great importance to the development of military applications of FOG. These countries are mainly committed to the development of low performance FOG equipment with drift rate greater than 1 (°)/h, Navy and air force. The first generation of FOG has been put into production. For example, PHINS series FOG, which is produced by IxSea Company in France, has been applied to inertial navigation and deep-water operation. Civitanavi Systems, Italy, based on proprietary FOG technology, developed a FOG [24] for attitude stabilization and navigation of satellite launchers.

FOG has different research and application in different countries. From **Table 4**, we can see the application of FOG in different companies in the world.
