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Home / Military / Fiber-optic gyroscopes (FOG) and ring laser gyroscopes (RLG) are high-precision inertial sensors for guidance, navigation, and control systems in aircrafts, missiles, ships and spacecrafts

Fiber-optic gyroscopes (FOG) and ring laser gyroscopes (RLG) are high-precision inertial sensors for guidance, navigation, and control systems in aircrafts, missiles, ships and spacecrafts

Satellite-based positioning is everywhere. The Global Positioning System (GPS) is a space-based radio-navigation system consisting of a constellation of satellites and a network of ground stations used for monitoring and control. GPS navigation systems use stored map information for determining optimal route selection based on a shortest path algorithm. This technique is quite successful in getting you to where you want to go in a reasonable time and is fault tolerant in the sense that it can automatically reroute in case of error.


However, In many environments in which military operates (inside buildings, in urban canyons, under dense foliage, underwater, and underground) have limited or no GPS access. Similarly, GPS signals can be significantly degraded or unavailable during solar storms. GNSS jammers are now being used by criminals or vehicle hijackers, as reported by the FBI: “… GPS tracking devices have been jammed by criminals engaged in nefarious activity including cargo theft and illicit shipping of goods.” Apart from jamming by adversaries, GPS signals are also subject GPS-spoofing attacks whereby a malicious entity generates a GPS-like signal designed to mislead GPS receivers.


One of the solutions is the integration of GPS with complementary technologies such as chip-scale atomic clocks and small inertial measurement units of the Micro-Electro Mechanical Systems (MEMS).  Inertial sensors at present lack the long-term stability of GNSS, but they are immune to jamming and spoofing since they do not rely on radio frequency signals. Such integration provides for more robust performance through sensor data fusion.


Inertial Navigation System (INS)

An inertial navigation system (INS) is a navigation device that uses a computer, motion sensors (accelerometers), and rotation sensors (gyroscopes) to continuously calculate by dead reckoning the position, the orientation, and the velocity (direction and speed of movement) of a moving object without the need for external references.  Often the inertial sensors are supplemented by a barometric altimeter and occasionally by magnetic sensors (magnetometers) and/or speed measuring devices. INSs are used on mobile robots and on vehicles such as ships, aircraft, submarines, guided missiles, and spacecraft.  It is also embedded in the mostly nowadays mobile phone for purpose of mobile phone location and tracking .


For aerial navigation, two types of INS are employed – stabilized platform INS and strap-down INS. Stabilized platform INS contain three or more accelerometers, as well as three or more gimballed spinning mass gyros which maintain platform alignment and stability when the aircraft is in motion. Strap-down INS also contain accelerometers and gyroscopes like RLGs, however, these are strapped down onto the frame of the airplane. This eliminates the need for gimbals used in stabilized platform INS that typically have reliability issues.



Inertial sensors are sensors based on inertia and relevant measuring principles. These range from Micro Electro Mechanical Systems (MEMS) inertial sensors, measuring only few mm, up to ring laser gyroscopes that are high-precision devices with a size of up to 50cm. Recent advances in the construction of microelectromechanical systems (MEMS) have made it possible to manufacture small and light inertial navigation systems. These advances have widened the range of possible applications to include areas such as human and animal motion capture.


Micro-Electro-Mechanical System (MEMS) gyroscopes are motion sensors that detect and measure the angular motion of an object. They measure the rate of rotation of an object around a particular axis: 1-axis, 2-axis, and 3-axis. Although initially used for expensive military applications, now they are also adopted for low-cost commercial applications of consumer electronics for Automotive, Defense, Industrial and Medical applications. The increased demand for mobile devices is also responsible for the growth of the MEMS gyroscopes market. The cost of MEMS gyroscopes is expected to reduce drastically in the next years, leading to an increment in the use of these devices.


The precision of MEMS gyroscopes has been improved in the last years with the help of batch production techniques and new gyroscope designs, they remain the biggest problem of MEMS inertial sensing technology and the main reason why previous technologies such as fiber-optic gyroscopes (FOG) or ring laser gyroscopes (RLG) are still vastly used in domains where high-precision sensors are necessary.



Gyroscopes are devices utilized for measuring and maintaining the orientation of an object in inertial space, at any given time. Earlier, mechanical gyroscopes were the norm. A mechanical gyroscope is based on the principle of conservation of angular momentum, which states that if no external torque acts on a system, the total angular momentum of the system remains constant. What this means is that a rotating object will keep spinning on an axis if no external torque is applied. Angular momentum is an essential physics characteristic which cannot be created or destroyed, only transferred. Mechanical gyroscopes consist of a disc, or spinning wheel, with an axle that assumes any orientation. Orientation changes rapidly when external torque is applied, however when the gyro is mounted in a gimbal, torque is minimized and the spin axis defined by the axle is thus stabilized.


Applications as guidance, navigation, and control systems in aircrafts, spacecrafts, and attitude systems in terrestrial vehicles, to give some examples, require compact, low cost, and reliable inertial navigation systems (INSs), which are equipped with increasingly accurate gyroscopes. For this reason, gyroscopes  are key elements, which are essential to obtain the desired sensitivity for all above applications. Gyros having a dynamic range up to ±1500°/s are required in both space and terrestrial vehicle navigation inertial measurement units (IMUs). Attitude and heading systems in aircraft and precision-spacecraft INSs require a gyro resolution typically on the order of 1°/h and 0.01–0.001°/h, respectively. Optical gyros based on Sagnac effect are the key components of IMUs which are widely used in the above mentioned applications.


Currently, the most widely used gyro technology for high-performance gyro systems is the optical fiber-based technology, specifically the technology based on interferometric fiber-optic gyro (IFOG). However, the counterpart of the IFOG made entirely in silicon wire waveguides on silicon-on-insulator (SOI) platform, called photonic integrated circuits (PICs) and, specifically, the integrated optics passive resonator gyro (IORG), has many advantages such as high robustness, theoretical sensitivity, and superior reliability due to its inherent characteristics of miniaturized structure, all-solid-state, and the combination between integrated optics and well-known CMOS fabrication technology. Thus, IORG has been considered as the next generation of resonant micro-optical gyros (RMOG) and a promising candidate in the field of inertial navigation. In particular, IORGs are very promising in terms of performance parameters such as low cost, compactness, light weight, and high reliability.


Principle of Optical Gyroscopes

Optical gyroscopes operate by sensing the difference in propagation time between counter-propagating beams traveling in opposite directions in closed or open optical paths. A certain rate of rotation induces a small difference between the time it takes light to traverse the ring in the two directions according to the Sagnac effect. This introduces a tiny separation between the frequencies of the counter-propagating beams, a motion of the standing wave pattern within the ring, and thus a beat pattern when those two beams interfere outside the ring. Therefore, the net shift of that interference pattern follows the rotation of the unit in the plane of the ring.


This rotation-induced phase difference physically consists in the Sagnac effect, being the basic operating principle of all-optical gyroscopes. Both FOG and RLG are optical gyros, all based on the Sagnac effect, which generates a phase or frequency difference proportional to the angular rate when two counter-propagating light beams in an optical resonant cavity suffer a rotation. The difference is that one propagates in the fiber and one propagates in the cavity, and the ring laser gyro has high precision.


Sagnac effect has also been demonstrated in semiconductor ring laser gyros (SRLGs). The interferometric fiber-optic gyro is to date a mature technology and was originally designed as a low-cost alternative to the ring laser gyro (RLG). Surprisingly, today IFOG can substitute the RLG both in terms of manufacturing costs and that of performance, gaining prominence in a series of military and commercial applications.


Ring laser gyroscopes for inertial navigation

Ring laser gyros are small, compact, lightweight, and radiation tolerant. Ring laser gyroscopes are lightweight, compact and self-contained, which allows for no friction. This is a major benefit, especially for inertial navigation systems (INS). Having no moving parts and being lightweight, prevents them from producing extra drag for the system in which they are set up. Moreover, today’s laser ring gyroscopes are significantly smaller than previous models, which make them the perfect choice for complex and sensitive technologies like inertial navigation systems, where accuracy, reliability, and efficient use of space, are key.


Ring laser gyro measures light frequency difference in two directions. The smaller surrounding area can have a relatively obvious frequency difference. Ring laser gyro expresses the rotational speed through fringe count and does not require closed-loop control. Ring laser gyro light travels in resonant cavity and is affected little by outside, so its precision is high, but the resonant cavity is expensive.


RLGs, while more accurate than mechanical gyroscopes, suffer from an effect known as “lock-in” at very slow rotation rates. When the ring laser is hardly rotating, the frequencies of the counter-propagating laser modes become almost identical. In this case, crosstalk between the counter-propagating beams can allow for injection locking so that the standing wave “gets stuck” in a preferred phase, thus locking the frequency of each beam to that of the other, rather than responding to gradual rotation.


Fiber optic gyro

The principle of fiber optic gyro can also be similar to that of ring laser gyro, but the various optical effects that actually occur make this method difficult to achieve. Fiber optic gyroscope measures the phase difference of the light in two directions. The gyroscope used will lock the phase difference of light in two directions through the Y waveguide device. In order to increase the phase difference/rotational speed coefficient, a larger enclosing area is required, that is, a longer optical fiber is required. The optical fiber has a low cost, but is susceptible to non-uniform thermal expansion and contraction due to temperature change and tension variation during winding.


MEMS use vibrating sensor technology (Coriolis Effect) to measure rotation. Unfortunately, this vibrating technology produces gyro noise, poor bias stability, and limited bandwidth. By contrast, KVH’s solid-state, Sagnac Effect-based FOGS are inherently low noise and offer excellent bias stability up to 1000 Hz.


Unlike FOGs, MEMS are also susceptible to harsh environmental conditions such as vibration, shock, and temperature. FOG-based inertial systems overcome MEMS’ issues and deliver superior performance, leading to improved safety in all operating environments. This factor is especially vital when autonomous platforms are transporting or coming into close contact with humans.


FOGs and FOG-based inertial solutions provide:

  • 10x better bias performance than competing MEMS
  • Low noise, excellent bias stability up to 1000 Hz
  • Superior reliability and accuracy
  • High resistance to vibration & shock affecting moving vehicles
  • Precision & repeatability that autonomous industrial robots require
  • Ensuring Performance through Rigorous Testing & Qualification


Compared with mechanical gyro or ring laser gyro, FOG is the best choice to replace mechanical gyro or ring laser gyro, with the following characteristics:
(1) There are few parts, the instrument is firm and stable, and it has strong resistance to shock and anti-acceleration;
(2) The length of wound fiber is longer, so that the detection sensitivity and resolution are several orders of magnitude higher than those of the ring laser gyro;
(3) no mechanical transmission parts, there is no wear problem, and thus have a longer service life;
(4) It is easy to adopt integrated optical circuit technology, the signal is stable, and can be directly used for digital output, and is connected with computer interface;
(5) Different accuracy can be achieved by changing the length of fiber or the number of times or the light propagates in the coil, and has a wider dynamic range;
(6) The propagation time of coherent beam is short, so the principle can be instantaneously started without preheating;
(7) It can be used together with a ring laser gyro to form a variety of sensors for inertial navigation systems, especially used as Strapdown Inertial Navigation Systems sensors;
(8) Simple structure, low price, small size and light weight.


Photonic Technology Brings a Cutting Edge to Inertial

New developments in photonic technology make high-performance inertial measurement accessible at lower size, weight and power. Many applications from driverless cars to UAVs can now take advantage of positioning that can independently bridge GPS outages from 2 minutes up to 10 minutes.


The focus narrows to the high-performance advantages now within reach for applications such as autonomous vehicles, which require centimeter-level precision for the duration of a few minutes, or navigation-grade performance regime of 0.01 ˚/hr. This area has been dominated by fiber optic gyros (FOGs), which until today were at a price too high to be used in conventional automobiles.


A new approach leverages silicon photonics to tackle this problem, providing a reliable, high-performance, scalable, smaller FOG to be used in these systems for autonomous and other challenging applications. Silicon photonics uses optical interconnects to provide faster data transfer both between and within microchips. In addition, the optical rays can carry far more data than electrical conductors. Silicon photonic devices can be made using existing semiconductor fabrication techniques.


The Photonic Integrated Circuit (PIC) integrated aboard the new gyroscope takes advantage of Si3N4/SiO2 polarization maintaining waveguides, low-loss waveguide couplers and high polarization extinction ratio to demonstrate these top-tier performance specifications:
• Bias Instability: 0.02 ˚/hr
• Angle Random Walk: <0.01°/√Hz
• Scale Factor Temperature: <50 ppm
• Linearity Error: <50 ppm
• Bias temperature: ≤1.0 ˚/hr, 1σ



The global Fiber Optics Gyroscope market was valued at USD 780.2 million in 2019 and it is expected to reach USD 956.9 million by the end of 2026, growing at a CAGR of 2.9during 2021-2026.


“Fiber optic gyroscopes are essential for fully autonomous vehicle control. FOGs and FOG-based IMUs will become key parts of the sensor mechanisms essential for accurate autonomous car performance. Considering this, focus on increasing autonomous vehicle production will bode well for the market in the coming years,” says FMI Analyst.


The COVID-19 pandemic has impacted the sales of semiconductor companies. The gyroscope manufacturing industry has also shown negative trends in response to the impact of COVID-19. The pandemic has disrupted most of the supply chain facilities in various industries, the FOG supply chains that mostly located in developed Asia and American regions has also got interrupted due to the impact of pandemic. The estimated sales of FOG sensors has dropped by 5% to 7% during the course of pandemic in Q1-Q2 2020. However, the global market has totally recovered soon and is estimated return to normal growth by Q4, 2021.



Fiber optic gyroscopes have many important applications in navigation and positioning systems, angular velocity sensors, stabilization equipment, and recently, in autonomous vehicle guidance backup systems for GPS-inaccessible area vibration. Gyroscope sensors are used in car navigation systems, electronic stability control systems of vehicles, motion sensing for mobile games, camera-shake detection systems in digital cameras, radio-controlled helicopters, robotic systems, etc. Extensive usage of gyroscopes as the primary product is driving the market in the field of navigation systems.


The GPS tracking device market is expected to reach more than US$ 4.5 Bn by 2031, at a CAGR of 11.4%. Factors that are driving growth of the market include increasing sales of commercial vehicles, small farm factors, affordable prices, and high ROI. This is one of the fasted-growing industries in the world. The use of fiber optic gyroscopes is huge in GPS technology.


Robotics is a fast-growing industry in today’s world. Because robots can sharply improve productivity and offset regional differences in labour costs and availability, they are likely have a major impact on the competitiveness of companies and countries alike. From 2021 to 2031, there is likely to be around 15% increase in shipments of robots, worldwide, and its market valuation is set to reach more than US$ 17.5 Bn by 2031. For robotic applications, gyro output can be used to determine rotation rates, altitude, or heading, and can be combined with other sensor inputs to determine position. A wide range of robots and autonomous vehicles are currently used in fiber gyros, and many more are likely to be used in the future.


As a recently developed multi-axis sensor, the inertial measurement unit (IMU) is an ideal sensor for measuring the attitude of a robot. Thus, IMUs play an extremely important role in humanoid robots. Robotics has become a rapidly growing industry in a short period of time. Over the past decade, global sales volume of industrial robots tripled. The International Federation of Robotics (IFR) released its annual World Robotics Report, which showed an estimated annual global sales value of US$ 18 billion in 2020.


IMUs are extensively used in robotics, which will drive the market. Owing to its huge demand, the inertial measurement unit market is estimated to be valued at over US$ 20 billion in 2021, and is expected to reach more than US$ 31 billion by 2031, at a CAGR of 6.5% over the forecast period, thereby driving the need for fiber optic gyroscopes.


Driver: Rising adoption of Unmanned Aerial Vehicles (UAVs)

Unmanned aviation vehicles (UAVs) are also named as autonomous drones that performs scouting missions. A UAV is used to perform multiple tasks, including mapping, target tracking, and offensive neutralizing. The most important module of the UAV is its autopilot mode, which allows its remote control. For enabling autopilot mode in UAVs, several types of sensors are required.


The main functional component of the autopilot is an Inertial Measurement Unit (IMU), composed of 3-axis FOGs and 3-axis accelerometers. Integration of these sensors improves the drone flight functionalities. UAVs are basically been used in military and defense sectors to locate enemies at cross-border regions. UAV manufacturers are integrating FOGs for building functionalities to measure angular velocity and linear movement.


Rapidly rising adoption of drones and unmanned aerial vehicles (UAVs) in the defense and commercial sectors has been recognized as a main driver for the market. The number of small non-commercial drones in the United States amounted to more than 1.15 million units in 2020, according to the Federal Aviation Administration (FAA). Commercial drone registrations amounted to about 450 K. This rapid increase in aerial vehicles is causing the market to grow further.



Fiber optic gyroscope market is segmented into four major sections such as fiber optic gyroscope by sensing axis (1-Axis, 2-Axis, and 3-Axis), device (Fiber Optic Gyrocompass, Inertial Measurement Units (IMUs), Inertial Navigation Systems, and Others), application (aeronautics and aviation, robotics, remotely operated vehicle guidance (Unmanned Underwater Vehicle (UUV), Unmanned Ground Vehicle (UGV), and Unmanned Aerial Vehicle (UAV)), military & defense, industrial, others), and region (North America, Latin America, Europe, East Asia, South Asia & Pacific, Middle East & Africa)

  • 1-Axis segment is dominating the global fiber optic gyroscopes market. The segment is estimated to register a market share of 42.8% by the end of 2021. However, 3-Axis segment is estimated to grow at the fastest rate, emerging dominant by the end of the forecast period.
  • Inertial navigation systems segment is dominating the global fiber optics gyroscope market. The segment is estimated to register a market share of 44.5% by the end of 2021, owing to increasing advancement in technology pertaining to navigation systems.
  • The remotely operated vehicle guidance application segment is expected to register high Y-o-Y growth rates throughout the forecast period. In terms of value, this segment is expected to expand at a CAGR of 11.0% during the forecast period.


Fiber optic gyroscopes are mainly used to stabilize aiming lines on remotely-controlled gun turrets and images, and also for avionics, integrated into the artificial horizons of military or civilian aircraft. Gyroscopes equipped with sensor are extremely robust. Global military expenditure is estimated to be more than US$ 2 trillion in 2021. The total is around 4 percent higher in real terms than in 2018, and 7.2 percent higher than in 2010. Despite tight defense budgets, worldwide demand for UAVs is projected to increase.


Military leaders say the growing capabilities of unmanned aircraft will revolutionize the conduct of warfare. The UAV market is estimated at more than US$ 20 Bn in 2021, and is projected to reach US$ 50 Bn by 2031, at a CAGR of around 15.5% from 2021 to 2031. Rise in the procurement of military UAVs by defense forces worldwide is one of the most significant factors projected to drive market growth. There is increasing use of UAVs in various commercial applications such as monitoring, surveying & mapping, precision agriculture, aerial remote sensing, and product delivery. For a UAV to function properly, fibre optic gyroscopes are extensively used to monitor its movements, which is driving market growth in the defense sector.


Regional Outlook

The U.S. will emerge as a leading market, backed by presence of several leading players. FMI forecasts it to account for 81.5% of North America market in 2021.

The European Commission allocated over €90 Mn for the European Defense Fund from the EU budget for 2017-19, which increased up to €13 Bn for the span of 2021. With a budget of US$ 50 Bn, the U.K. is the largest military spender in Europe.


In 2020, the British government approved the largest rise in its defense budget since the end of the Cold War, with £16.5 billion (US$ 21.9 billion) over four years. This will create the need for latest aerospace technologies, which will drive the market for fibre optic gyroscopes, estimated to expand at the rate of close to 5% CAGR over the next ten years. Demand in the U.K. is projected to rise at 10.1% in 2021, thanks to increasing budget allocated towards military and defense.


Germany, along with the U.K., dominates the European fiber optic gyroscope market, due to increasing number of automobile manufacturing facilities in the country. The automobile industry in Germany is likely to expand at a CAGR of around 4% during the forecast period 2021-2031. Fiber optic gyroscopes are extensively used in cars for automatic motion control and GPS. Increasing sales of automobiles in Germany will be a large contributor to the growth of the fiber optic gyroscope industry, estimated to expand at a CAGR of close to 5% during the forecasted years of 2021-2031.


The military sensors market in the Asia Pacific region is projected to progress at the highest CAGR among any region from 2021 to 2031. Growth can be attributed to increased procurement of defense systems by countries such as China and India. Ongoing military modernization programs in countries such as Japan and Australia are also fuelling market growth in Asia Pacific. Countries in this region are continuously increasing their defense capabilities by procuring advanced systems. Increase in political tensions between countries is putting governments on high alert, and they are increasing their defense budgets to prepare for any kind of emergency. China, followed by India, has the highest military budget in the Asian continent.


In 2021, the Chinese government reported an estimated official defense budget of around US$ 200 Bn, which will be an increase of more than 5.5% as compared to the previous year, while the Indian military budget is estimated to grow by 6.8% to US$ 80 Bn. The tremendous increase in the military budgets of both these countries is enabling them to invest in the latest aerospace and aviation technologies, which involve the extensive usage of fiber optic gyroscopes for motion control.


The value of motor vehicles produced by the automotive industry in Japan amounted to almost 22 trillion Japanese yen in 2020, which makes it the biggest automobile sector in the world. Japan is well known as the automobile industry’s manufacturing hub; driverless vehicles are giving rise to increased adoption of fiber optic-gyroscopes. End-user companies are willing to invest in the measurement of orientation in several device monitoring systems for their safety, which use fiber optic gyroscopes, thereby aiding market growth in the country.



Growth dynamics of the aerospace and defense industry are likely to have a significant impact on the manufacturing strategies of market players and the competitive environment in the fiber optic gyroscope market over the coming years.


Some of the leading players are Sensonor AS (Norway), Analog Devices, Inc. (US), Epson Electronics America, Inc. (US), Kionix, Inc. (US), Systron Donner Inertial (US), VectorNav Technologies (US), LORD Corporation MicroStrain(r) Sensing Systems (US), Murata Manufacturing Company, Ltd. (Japan), Panasonic Corporation (Japan), MEMSIC, Inc. (US), Bosch Sensortec GmbH (Germany), Freescale Semiconductor, Inc. (US), Colibrys Ltd. (Switzerland), Moog Inc. (US), Texas Instruments, Inc. (US), Silicon Sensing Systems Ltd. (UK), STMicroelectronics (Switzerland), InvenSense Inc. (US), Maxim Integrated Products Inc. (US).


Others include KVH Industries, Inc., EMCORE Corporation, FIBERPRO, Inc., Saab, Honeywell, Tamagawa Seiki Co., Ltd., Optolink, NedAero Components B.V, iXblue, Fizoptika, Safran, Cielo Inertial Solutions, Ericco International, Fibernetics LLC, and Northrop Grumman Sperry Marine B.V.


  • EMCORE Corporation introduced its EN-150 Inertial Measurement/Navigation Unit, which is highly suitable for dismounted soldiers and weaponry, platform stabilization, and unmanned aerial vehicles where is GPS is not available. It replaces Ring Laser Inertial Measurement Units (IMU) with smaller size and high-performance fiber optic gyroscope-based inertial measurement.
  • Another player in the fiber optic gyroscope market, KVH Industries, Inc., recently launched its new fiber-optic gyroscope-based IMU with a 25g accelerometer. This new IMU is designed for dynamic applications with high levels of shock, vibration, and acceleration. Furthermore, the company collaborated with VectorNav Technologies LLC, a provider of embedded navigation solution, to combine the reliability and precision of KVH’s fiber optic gyroscope-based IMUs with high-performance navigation systems by VectorNav to capitalize on a wide range of its industrial applications.




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