The Manufacturing Process of Fiber Optic Gyroscope

Fiber optic gyroscope has become the preferred core component for high-precision and high reliability inertial navigation systems due to its significant advantages such as all solid state design, no moving parts, fast start-up, long lifespan, wide dynamic range, and strong resistance to impact and vibration. However, behind the outstanding performance of fiber optic gyroscopes is their extremely precise and complex manufacturing process. From the selection and processing of specialized optical fibers, the coupling and alignment of precision optical components, to the precision winding and curing of the core sensing coil, and further to the integration of complex electronic systems and the implementation of sophisticated environmental compensation algorithms – each production stage embodies the crystallization of cutting-edge materials science, precision optical engineering, microelectronics technology, and advanced control theory. Even the slightest deviation during the manufacturing process can have a decisive impact on the accuracy, stability, and reliability of the final product.

Below is a detailed introduction to the production process of fiber optic gyroscope.

1.       Manufacturing of fiber optic rings

The core component of a fiber optic gyroscope is the fiber ring, and its manufacturing process is crucial. Firstly, high-quality optical fibers need to be selected and wound into a ring shape through precise winding processes. During this process, it is necessary to strictly control the tension of the optical fibers, the diameter and density of the winding ring to ensure the performance and stability of the fiber ring. After winding, adhesive coating and curing are performed for shape fixation. Subsequently, the fiber optic ring needs to undergo temperature cycling aging to eliminate internal residual stress and enhance mechanical stability through epoxy coating.

2.       Optical Device Integration

After the fiber optic ring is manufactured, it needs to be precisely assembled with other optical components. Mainly includes the assembly of Y-waveguide modulators and the integration of light sources and detectors to ensure smooth and stable optical paths. In addition, strict performance testing of the assembled components is required to ensure that they meet the design requirements.

3.       Circuit system construction

The construction of circuit systems includes the design of signal processing circuits and closed-loop feedback circuits. FPGA serves as the core processor to generate square wave/sawtooth wave modulation signals to drive the Y waveguide, bias the operating point to the sensitive area, and calculate the phase difference (Δφ) of the interference signal output by the detector, which is converted into angular velocity (Ω). Dynamically compensate for Sagnac phase difference through digital closed-loop control to improve linearity and dynamic range.

4.       Whole machine assembly and testing

After completing the manufacturing of fiber optic rings, optical components, and circuit boards, the next step is to proceed with overall assembly. This process includes environmental adaptability encapsulation and performance calibration and compensation. The optical and electronic units are sealed inside a metal shielding shell to isolate temperature and humidity changes and electromagnetic interference. Military grade products use titanium alloy shells to enhance impact resistance. Subsequently, a series of tests and calibrations were conducted on the fiber optic gyroscope, including zero bias calibration, temperature compensation, and threshold testing, to ensure that all performance indicators meet the expected requirements.

The key process difficulties in the manufacturing process of fiber optic gyroscopes mainly include the following:

1. Precision winding of fiber optic coils

The stress generated during the winding process of fiber optic coils can cause polarization errors. The solution is to use polarization maintaining fibers and adopt a symmetrical winding process.

2. Packaging and Interconnection of Integrated Optical Chips (Y-Waveguides)

Y-Waveguides are the core multifunctional integrated optical devices of FOGs. During the packaging and interconnection process, the alignment accuracy of the optical axis is extremely high. the solution to this difficulty is to use an active alignment system and a polarization maintaining fusion splicer.

3. Temperature drift

Temperature changes can cause gyroscope phase drift, affecting measurement accuracy. The solution is to use multi-stage depolarizers and adopt segmented temperature compensation algorithms to eliminate the impact of temperature drift.

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