After over a decade in the inertial navigation technology field, I’ve come to regard four-in-one integrated devices as the unsung heroes in the evolution of fiber optic gyroscopes (FOGs)—quietly overcoming the long-standing bottlenecks of size, cost, and reliability that once confined FOGs to high-end aerospace and defense sectors. Unlike four-in-one components in the display or semiconductor industries, those designed specifically for FOGs serve a more precise purpose: integrating core optical and electronic functions into a compact module to unlock the technology’s civilian potential.
Traditional FOGs rely on discrete components—light sources, couplers, phase modulators, and detectors—each requiring independent packaging and calibration. This not only results in bulky, overweight gyros but also drives costs up exponentially; the cost per gram of early FOGs even exceeded that of gold, limiting their application to missiles, satellites, and large ships. The emergence of four-in-one devices changed this scenario by integrating these four core components into a single silicon-based module. Leveraging silicon photonics and heterogeneous integration processes, the footprint of high-end designs can be reduced to less than 0.2 square centimeters, only about one-tenth the size of discrete assemblies.
What non-professionals often overlook is that FOG four-in-one devices are by no means simple component combinations, but carefully engineered to alleviate the core pain points in FOG operation. For example, integrating the phase modulator and detector on the same substrate minimizes non-reciprocal phase errors caused by temperature fluctuations and mechanical vibrations, which is crucial for maintaining sub-degree angular accuracy. Meanwhile, it simplifies the optical alignment process—a time-consuming and labor-intensive step in traditional FOG assembly that often introduces human error and reduces yield rates.
I still recall a 2024 project with an autonomous driving company, where we replaced a discrete-component FOG with a prototype equipped with our self-developed four-in-one silicon photonic module. The results were transformative: the gyro’s weight was reduced by 65%, power consumption by 40%, and most importantly, the unit cost dropped from the ten-thousand-yuan range to the thousand-yuan range—finally making FOG-level precision accessible at MEMS gyro prices. It performed flawlessly in tests in tunnels and underground garages without GPS signals, maintaining stable positioning for over 20 minutes.
Of course, four-in-one devices for FOGs are not without challenges. The biggest hurdle is balancing integration level and optical performance—silicon’s inherent limitations as a light-emitting material force us to use heterogeneous bonding of III-V materials such as indium phosphide, which undoubtedly increases manufacturing complexity. Coupling efficiency is another major pain point: the mode field size of integrated waveguides is extremely small (about 0.15 micrometers), requiring sub-micron alignment precision when docking with fiber coils, which has pushed the performance limits of automated assembly equipment.
Early mass production also faced yield difficulties. The multi-step process—from wafer bonding and waveguide etching to final calibration—means that even minor process variations can render the entire module ineffective. We spent months optimizing the silicon-on-insulator (SOI) + silicon nitride monolithic integration process, ultimately increasing the yield from 60% to over 85% and laying the foundation for commercial large-scale production.
Interestingly, the industry’s perception of such four-in-one devices has undergone a dramatic transformation. A few years ago, they were regarded as a "compromise" between discrete high-precision components and low-cost MEMS; today, they are recognized as the core enabler of FOG civilianization, bridging the gap between aerospace-grade performance and commercial cost-effectiveness.
Domestic manufacturers have been at the forefront in this field. Enterprises such as CETC 14th Research Institute and Chongqing Shuaiwei Technology have optimized FOG four-in-one modules through 130nm and 180nm silicon photonics processes, achieving a bias stability of less than 0.1°/h for mass-produced devices at a fraction of the cost of foreign counterparts. Even regional manufacturers like Chongqing United Microelectronics are expanding the production capacity of integrated FOG transceiver chips, consolidating China’s position in this critical niche market.
These devices embody the core truth of FOG development: miniaturization and cost control do not have to come at the expense of precision. Focusing on system-level integration rather than individual component upgrades, four-in-one modules have redefined the application boundaries of FOGs. They are by no means a "stepping stone," but a foundational technology that is pushing FOGs into new markets such as autonomous driving, deep-sea robotics, and precision agriculture.
The experience accumulated from FOG four-in-one devices is now influencing the development of next-generation technologies such as photonic crystal FOGs. We are applying the same integration concept to tri-axis gyro designs, integrating three four-in-one modules into a single chip to achieve full 3D motion sensing. AI-driven calibration technology, optimized to compensate for integration-induced noise, also makes these modules more robust in harsh environments—experience that directly informs our research and development of silicon photonic gyros.
In a field obsessed with breakthroughs in fiber coil sensitivity or modulator speed, it is easy to overlook the understated impact of four-in-one devices. They have transformed FOGs from niche aerospace components into accessible, scalable tools—and this process has proven that integration, rather than the improvement of a single performance metric, is the key to ushering in a new era of inertial navigation technology. Their contribution to popularizing FOG precision will outvalue even the most advanced next-generation designs.
Ihre Nachricht muss zwischen 20 und 3.000 Zeichen enthalten!
