Pseudo-random-bit-sequence phase modulation for reduced errors in a fiber optic gyroscope.

Area of Science:

• Optical Engineering
• Inertial Navigation Systems

Background:

• Fiber optic gyroscopes (FOGs) are critical for inertial navigation.
• Achieving low noise and drift in FOGs is essential for high-precision applications.
• Traditional laser sources can introduce noise limitations in FOG performance.

Purpose of the Study:

• To demonstrate significantly reduced noise and drift in a laser-driven FOG.
• To investigate the effect of laser coherence on FOG sensor performance.
• To establish new benchmarks for FOG noise and drift levels.

Main Methods:

• Interrogating the FOG sensor with a low-coherence laser.
• Broadening the laser's optical spectrum using an electro-optic phase modulator.
• Employing sinusoidal or pseudo-random bit sequence (PRBS) waveforms for modulation.

Main Results:

• Laser coherence was reduced by broadening the spectrum from 10 MHz to over 10 GHz using PRBS modulation.
• Measured FOG noise achieved was 0.00073 deg/√h.
• Measured FOG drift was 0.023 deg/h, below aircraft inertial navigation requirements.

Conclusions:

• Modulating laser coherence effectively reduces noise and drift in FOGs.
• The achieved noise and drift levels represent the lowest reported for laser-driven FOGs.
• This method shows potential for enhancing the performance of inertial navigation systems.