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Signal-to-Noise Ratio of Brillouin Grating Measurement with Micrometer-Resolution Optical Low Coherence Reflectometry
Kazumasa Takada1, Shin-Ichi Satoh1, Akiya Kawakami1
1Division of Electronics and Informatics, Faculty of Science and Technology, Gunma University, 1-5-1 Tenjin, Kiryu, Gunma 376-8515, Japan.
Sensors (Basel, Switzerland)
|February 14, 2020
Summary
Researchers identified speckle-like noise in Brillouin grating measurements using optical low coherence reflectometry (OLCR). Attenuating pump light significantly improved signal-to-noise ratio (SNR), enabling micrometer-resolution diagnosis of fiber optic components.
Area of Science:
- Optics
- Photonics
- Materials Science
Background:
- Speckle-like noise is a primary limitation in micrometer-resolution Brillouin grating measurements using optical low coherence reflectometry (OLCR).
- This noise arises from the interaction between the Stokes signal and pump-induced beat noise during square-law detection.
Purpose of the Study:
- To analyze the dominant noise source in Brillouin grating measurements with OLCR.
- To establish a relationship between signal-to-noise ratio (SNR) and dynamic range (DR).
- To demonstrate improved measurement accuracy through noise reduction techniques.
Main Methods:
- Calculated the SNR based on the ratio of Stokes signal magnitude to beat noise variance.
- Investigated the impact of pump light power on noise levels.
- Applied pump light attenuation to a balanced mixer to enhance SNR.
Main Results:
- The SNR was found to be proportional to the square root of the dynamic range (DR).
- A 20 dB DR resulted in an SNR of only 7, with signal fluctuations of ±14%.
- Attenuating pump light by 55 dB increased SNR to 24.
Conclusions:
- Pump light attenuation is a critical factor for improving SNR in OLCR-based Brillouin grating measurements.
- The enhanced SNR allows for micrometer-resolution diagnosis of fiber optic components like connectors and couplers.
- This work provides a pathway for more accurate and reliable optical component analysis.
