Abstract

In view of the poor scale factor stability of the interferometric fiber optic gyroscope (IFOG), it is a creative method to use laser to drive the IFOG for its better frequency stabilization characteristics instead of the broadband light source. As the linewidth of laser is narrow, the errors of coherent backscattering, polarization coupling, and Kerr effect are reintroduced which cause more noise and drift. This paper studies laser spectrum broadening based on external phase modulation of Gaussian white noise (GWN). The theoretical analysis and test results indicate that this method has a good effect on spectrum broadening and can be used to improve the performance of the laser-driven IFOG. In the established closed-loop IFOG, a four-state modulation (FSM) is adopted to avoid temperature instability of the multifunction integrated-optic chip (MIOC) and drift caused by the electronic circuit in demodulation. The experimental results show that the IFOG driven by broadened laser has the angular random walk noise of 0.003 8 °/√h and the drift of 0.017 °/h, which are 62% and 66% better than those without modulation respectively, of which the drift has reached the level of the broadband light source. Although the noise still needs further reduction, its scale factor stability is 0.38 ppm, which has an overwhelming advantage compared with the traditional IFOG.

Highlights

  • As a kind of rotation rate sensor based on the Sagnac effect [1], interferometric fiber optic gyroscope (IFOG) has been developed for over forty years

  • The performance of the IFOG driven by broadened laser should be compared with the intrinsic laser and superluminescent diode (SLD) simultaneously to study the improvement with modulation and the potential for laser replacing broadband light source

  • The noise is still relatively high compared with 0.001 8 °/√h of the SLD in the same IFOG system, but its performance could be promoted by using the less loss optical fiber, which has more influence on the laser-driven IFOG than the broadband light source because of coherent backscattering [12]

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Summary

Introduction

As a kind of rotation rate sensor based on the Sagnac effect [1], interferometric fiber optic gyroscope (IFOG) has been developed for over forty years. Compared with its main competitor, ring laser gyroscope (RLG), the IFOG does not need high-precision processing of the optical mirror and strict sealing of the cavity or ignition voltage of several thousand volts. It effectively overcomes the self-locking phenomenon and has the characteristics of simple structure, low cost, small volume, and light weight [6,7,8]. The most serious problem needing to solve in this process is to improve the scale factor stability of the IFOG, which is usually driven by the broadband superluminescent diode (SLD) or superfluorescent fiber source (SFS) and its average wavelength stability is much worse than that of laser [9]. As there is no temperature control or vibration isolation, better results can be available by overmodulation, signal processing, and temperature modeling

External phase modulation of the GWN
IFOG system
Closed-loop detection scheme
Experimental results
Conclusions
Full Text
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