In this paper, a novel optical approach to double the sensitivity to angular rate of interferometric fiber optic gyroscope (IFOG) is proposed. Two fiber polarization combiner/splitters (FPCSs), as the key components, are added in the traditional IFOG light path. The FPCSs are able to either combine two orthogonal polarizations transmitting at two different polarization-maintaining fibers (PMFs) into the two orthogonal axes of one PMF, respectively, or split two polarizations transmitting at the two orthogonal axes of one PMF into two polarizations to transmit at two different PMFs, respectively. Through the specific placement and coupling of these two FPCSs, the incident light can transmit twice along the polarization-maintaining fiber coil (PMFC). The novel approach is verified experimentally and the experimental results show consistency with the theoretical analysis. The proposed approach is able to double the sensitivity of IFOGs and can increase the signal-to-noise ratio (SNR) without increasing the length of PMFC, which is very susceptible to environmental influences and is of great significance in the technical improvement of IFOGs, as well as the miniaturization of IFOGs.

A coupling effect in the single-mode fiber coil (SMFC) of a depolarized interference fiber optic gyroscope (De-IFOG) under time-varying temperature and magnetic field, which can cause a serious nonreciprocal phase error, is revealed. In this paper, the mechanism of the coupling effect is thoroughly studied and the related theory is derived in detail. Simulations and experiments are carried out to verify the validity. The experiments show a peak-to-peak value error of about 50 °/h in the SMFC when the magnitude of magnetic field is 10 Gauss and the temperature uniformly increases from 10 to 60 °C at the rate of 36 °C/h, which cannot be neglected in the applications of De-IFOGs.

A novel fiber-optic magnetic field sensor, based on a Sagnac structure, is proposed with the approach of polarization interference detection. The sensor takes advantage of common path interference, combining with a high magnetic field sensitivity sensing unit, composed of magneto-optical crystal, and magnetic field concentrators, to achieve high resolution, high stability, and large dynamic measurement of DC magnetic field signals. In this paper, the theoretical model is established and the related theory is derived in detail. The key technologies in the system are thoroughly investigated and verified. Experimental research on the proposed system is demonstrated and the results show that a DC magnetic field resolution of 5.6 nT and a dynamic range of larger than 70 dB is achieved. Furthermore, the linearity of the system is greater than 99.8% and the instability is less than 0.5%.

A direct current (DC) Sagnac magnetic field sensor is a kind of fiber sensor based on alternate current magnetic field (ACMF) demodulation and empirical mode decomposition (EMD) to detect the magnetic field by measuring the phase variety caused by direct current magnetic field (DCMF). Commonly, Sagnac DCMF sensors can improve the magnetic detection sensitivity by using high Verdet constant (HVC) medium, which is expensive to prepare, or optical resonant cavity. However, the polarization diffraction in cavity restricts the performance of these devices. Meanwhile, none of them can suppress the electrical noise of the system such as 1/f noise. In this paper, we use ACMF modulation to couple the phase containing the DCMF information into the amplitude of the fundamental frequency component of the interference signal. Then we demodulate the signal by EMD to extract the fundamental frequency component. The designed sensor demonstrates a sensitivity of 4.651 mV/μT with an accuracy of 1.649 nT in the magnetic field range of 0-40 mT. It has the advantages of high stability, anti-electromagnetic interference and miniaturization.

This research investigates the time-of-flight (TOF) ranging precision of a dual-comb system, utilizing three distinct phase-locking methods. We continuously collected ranging values over a period of approximately 20 min, then compared the ranging precision across averaging times spanning from 1 µm to 262 s, during which the Allan deviation floor of the TOF ranging is also determined. The results highlight that the dual-comb with two frequency modes locked to two cavity-stabilized continuous-wave (CW) lasers sustains superior ranging precision, achieving an Allan deviation floor of 35 nm at an averaging time of 8 s. Locking the repetition frequencies to a hydrogen maser results in lower precision in comparison to the free-running method for averaging times under 16 µm, and thereafter matches to the free-running precision up to an averaging time of 8 s. These findings are further analyzed through the relative phase noise of the dual-comb’s repetition frequencies.