Minimizing Specular Reflections in a Sagnac based Fiber Gyro

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SUMMARY

The discussion focuses on minimizing specular reflections in a Sagnac-based fiber optic gyroscope for an airspeed flowmeter project. The user is facing challenges with backreflections that obscure weak signals, contrasting their DIY approach with a commercial solution that successfully isolates phase-shifted signals. Key techniques mentioned include phase modulation, short coherence length sources, and addressing Rayleigh scattering and birefringence. The user seeks guidance on achieving lower backreflection levels, ideally around -70 dB, without compromising system alignment.

PREREQUISITES
  • Understanding of Sagnac effect in fiber optics
  • Knowledge of phase modulation techniques
  • Familiarity with Rayleigh scattering and birefringence in optical fibers
  • Experience with fiber optic component alignment and backreflection measurement
NEXT STEPS
  • Research phase modulation methods for signal isolation in fiber optics
  • Explore techniques for minimizing backreflection in fiber optic systems
  • Investigate the impact of fiber alignment on signal integrity
  • Learn about advanced optical sources with short coherence lengths
USEFUL FOR

Optical engineers, researchers in fiber optics, and developers working on precision measurement systems who aim to enhance signal detection in low-noise environments.

Diyon
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My project is to build an airspeed flowmeter using the design of a signac fiber optic based gyro. There is a group that has already accomplished this task (http://www.ncbi.nlm.nih.gov/pubmed/18301479), however they used a commercial fiber gyroscope whereas I am trying to build the entire setup myself.

The problem I'm encountering is the specular backreflections off my fiber optic components are washing out my inherently extremely weak signal. After a lot of reading, I have come to the conclusion that it must be their phase modulation that is somehow isolating the phase shifted signal through the DC noise of the reflections. All the other components (short coherance length source+Phase Shift) are to deal with separate problems (Rayleigh Scattering and Birefringence of the fiber).

Can anyone explain why they are able to sense such a small signal, or how they are able to eliminate the reflections off their fiber components? I found the most ideal case would be -70db of backreflection after using 8 degree cut fiber and misaligning it, both of which I am hesitant to do since it would misalign my system and my signal i calculated is -60-80db compared to my constructive signal.
 
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Bump, if anyone can point me in the right direction of a good resource that would be helpful as well.
 

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