As one of the most successful applications in optical fiber sensing, interferometric fiber optic gyroscope (IFOG) has become the ideal choice for inertial navigation systems, and has been widely used in the fields of aviation, aerospace, navigation, and land. Exploring the theoretical noise limit and improving the practical precision are the objectives of FOG investigations, and the advanced photonic crystal fibers offer powerful approaches and potential to achieve these goals. In this review, the progress of photonic crystal fibers in FOGs research and applications for angular velocity measurement have been reviewed, together with the advanced technologies for improving the FOG's precision and reducing its volume.

Chip-scale interferometric fiber optic gyroscope (IFOG) has caught growing attention for its huge application potential in the low-cost consumer electronics market. In this paper, a novel three-axis IFOG is proposed and assembled with an integrated coupler chip (ICC) fabricated on the silica platform. The ICC realizes bidirectionally multichannel optical interconnection without waveguide crossings. The test results indicate the weak wavelength dependence and comparatively low insertion loss at 0.85μm of the ICC. With ~900m polarization-maintaining fiber coils, the three-axis IFOG exhibits a long-term stability of <0.16 °/h, which satisfies the requirements of the tactical grade systems. The novel IFOG scheme with ICC paves the way for the research on chip-scale multi-axis IFOGs.

We demonstrate a tunable single-longitudinal-mode (SLM) narrow linewidth erbium-doped fiber (EDF) ring laser (EDFRL) in a cost-effective way. The laser incorporates an unpumped-EDF-based saturable absorber (SA) and a self-injection feedback loop for mode selection. The EDFDRL exhibits linear tunability of 12.57 pm/°C from 15 °C to 45 °C with a maximum tuning range of 0.3664 nm. At a pump current of 200 mA, we achieve a SLM EDFRL characterized by a high OSNR of 75 dB and an ultra-narrow linewidth of 330 Hz. Furthermore, it shows an excellent wavelength stability, with a maximum fluctuation of only 11.23 pm.

The mechanism of fiber coil polarization properties' effect on the performance of a fiber optical gyroscope (FOG) is investigated with analysis of secondary wave trains' polarization evolution and interference in the fiber coil. Based on the optical model, the simulation demonstrates that the bias error varies nonlinearly with the fiber coil polarization crosstalk, and the experiment verifies the analysis and simulation result, so some measures are promoted to reduce the bias' dependence on the fiber coil's polarization properties, which is significant for improving environmental adaptability and long-term stability of the FOG.

Temperature-pressure cross-sensitivity is a thorny issue that affects the measurement accuracy of polymer diaphragm pressure sensors. To alleviate the aforementioned issue, we demonstrate a novel optical Fabry-Perot interferometer (FPI) pressure sensor based on polydimethylsiloxane (PDMS) polymer diaphragm-formed vacuum microcavity. A technique of liquid encapsulation with vacuum pump oil is innovatively proposed. The vacuum FP microcavity is fabricated by assembling a capillary filled with vacuum pump oil and a fiber-tip FP cavity formed by the PDMS polymer diaphragm in a vacuum environment. The structural dimension of the sensor and the initial pressure in the vacuum microcavity can be precisely and conveniently controlled. The optimal parameters of the sensor are determined through finite element method(FEM) to help to achieve low temperature-pressure cross-sensitivity. From the experimental results, the proposed FP pressure sensor with a polymer diaphragm thickness of 33.1 μm exhibits a wavelength pressure sensitivity as high as 1.58 nm/kPa in the range of 0-2 kPa and a temperature-pressure cross-sensitivity as low as 0.10 kPa/°C, which proves that the temperature crosstalk is effectively suppressed. Moreover, the proposed sensor has several advantageous characteristics including cost-effectiveness, reliable repeatability, long-term stability, and mass-producible, which makes it suitable for monitoring small-range static hydrostatic pressure precisely over a dynamic temperature range.

We propose a method based on the white-light interference technique for measuring the Verdet constant of a polarization-maintaining air-core photonic bandgap fiber (PM-PBF). The experimental results show that the Verdet constant of the PM-PBF is ~3.3 mrad/T/m for the broadband light with a spectral width of ~38 nm and a mean wavelength of ~1550 nm, which is ~124 times less than that of a conventional stress-induced birefringent fibers called PANDA fibers (~0.41 rad/T/m for the same broad-spectrum light). The results indicate that the nonreciprocal error induced by the Faraday effect in a fiber optic gyroscope (FOG) made of the PM-PBF is theoretically ~25 times less than that of a conventional FOG made of the PANDA fiber when other conditions, such as the fiber twist, fiber coil area, and so on, are the same.