Zuchen Zhang

Investigation of residual core ellipticity induced nonreciprocity in air-core photonic bandgap fiber optical gyroscope

Air-core photonic bandgap fiber (PBF) is an excellent choice for fiber optic gyroscope owing to its incomparable adaptability of environment. Strong and continuous polarization mode coupling is found in PBFs with an average intensity of ~-30 dB, but the coupling arrives at the limit when the maximum optical path difference between the primary waves and the polarization-mode-coupling-induced secondary waves reaches ~10mm, which is corresponding to the PBF length of ~110 m according to the birefringence in the PBF. Incident light with the low extinction ratio (ER) can suppress the birth of the polarization-mode-coupling-induced secondary waves, but the low-ER light obtained by the conventional Lyot depolarizers does not work here. Consequently, a large nonreciprocity and a bias error of ~13°/h are caused in the air-core photonic bandgap fiber optical gyroscope (PBFOG) with a PBF coil of ~268 m.

Analysis and simulation of a fiber optical gyroscope with Shupe error compensated optically

Shupe error, a kind of bias error over temperature-varying environments, still exists even with strict quadrupolar winding pattern, and it affects the environment adaptability of fiber optical gyroscope (FOG) and limits its application. A novel configuration to realize optical compensation for Shupe error in FOG is promoted, employing the opposite polarity of Shupe error in two FOGs working with polarization-maintained (PM) fiber’s fast and slow axis, respectively, in a single PM fiber coil. Analysis is also made for polarization non-reciprocity (PNR) in both FOGs, based on which the optimum coupling angles between integrated optic chip and PM fiber coil are obtained to guarantee that Shupe error arising from both FOGs can be counteracted to zero, and PNR error is suppressed to be minimum at the same time.

Backward Secondary-Wave Coherence Errors in Photonic Bandgap Fiber Optic Gyroscopes.

Photonic bandgap fiber optic gyroscope (PBFOG) is a novel fiber optic gyroscope (FOG) with excellent environment adaptability performance compared to a conventional FOG. In this work we find and investigate the backward secondary-wave coherence (BSC) error, which is a bias error unique to the PBFOG and caused by the interference between back-reflection-induced and backscatter-induced secondary waves. Our theoretical and experimental results show a maximum BSC error of ~4.7°/h for a 300-m PBF coil with a diameter of 10 cm. The BSC error is an important error source contributing to bias instability in the PBFOG and has to be addressed before practical applications of the PBFOG can be implemented.

Reflection-induced bias error in an air-core photonic bandgap fiber optic gyroscope.

Analysis of the bias error induced by reflections in an air-core photonic bandgap fiber gyroscope is performed by both simulation and experiment. The bias error is sinusoidally periodic under modulation, and its intensity is related to the relative positions of the reflection points. A simple and effective method for the suppression of the error is proposed, and it has been verified experimentally.

A fiber optical gyroscope with shupe error compensated optically.

Fiber optical gyroscope (FOG) is a kind of angle velocity sensor developed in recent 30 years, with characteristics of small volume, solid structure, fast startup and so on. FOG is an important component for high-precision navigation and control of autonomous robots. Shupe error, a kind of bias error in FOG over temperature varying environments, still exists even with strict quadrupolar winding pattern, and it affects the environment adaptability of FOG and limits the navigation performance of autonomous robots, especially in harsh environment. A novel configuration to realize optical compensation for Shupe error in FOG is promoted in our earlier paper, employing the opposite polarity of Shupe error in two FOGs respectively working with polarization maintained (PM) fibers fast and slow axis in a single PM fiber coil. We have given a thorough theoretical analysis of this novel FOG in the earlier paper. In this paper, we mainly focus on the experimental verification of the FOG, including its closing-loop operation, static performance, basic principle of compensation of Shupe error, and choose of the coupling angles between fiber coil and integrated optic chip to make PNR error minimum. The experiment results agree well with the theoretical analysis, and the feasibility of the novel FOG is proved.