New Method Estimates Modulation Amplitude for Cost-Effective Sensing

Researchers from the Shibaura Institute of Technology have developed a new technique to estimate modulation amplitude accurately and determine spatial resolution without additional devices. This study was published in the journal Scientific Reports.

Optical fibers must exhibit Brillouin scattering to achieve high spatial resolution in infrastructure monitoring and sense temperature and strain. Traditionally, sophisticated and costly apparatus is needed to measure the modulation amplitude in Brillouin scattering.

Researchers at the Shibaura Institute of Technology suggested a new technique for determining the modulation amplitude using Rayleigh scattering without requiring extra hardware or system modifications.

The phenomenon known as Brillouin scattering occurs when thermally generated acoustic vibrations scatter light in an inelastic manner. By analyzing how light scatters in response to different stimuli, Brillouin-based optical fiber sensing can quantify temperature and strain distributions.

This method is particularly effective when applied to correlation-domain techniques, such as Brillouin optical correlation-domain analysis and Brillouin optical correlation-domain reflectometry (BOCDR), which offer high spatial resolution and random accessibility to various measurement points. BOCDR, which utilizes spontaneous Brillouin scattering, enables single-end accessibility, making it a versatile tool for different sensing applications.

In BOCDR, the light's modulation amplitude and frequency dictate the spatial resolution. Since modulation amplitude is correlated with peak light intensity, accurate measurement usually necessitates using expensive, large-scale equipment such as heterodyne detection systems or optical spectral analyzers. These specifications raise expenses and complicate the experimental setup.

Recently, a group of Japanese academics, led by Associate Professor Heeyoung Lee from Shibaura Institute of Technology (SIT), and comprising Yosuke Mizuno from Yokohama National University and Keita Kikuchi from SIT, developed an innovative way to tackle this problem.

We have developed a new method to accurately estimate the modulation amplitude that determines spatial resolution in BOCDR without requiring additional equipment or modifications to the experimental setup.

Dr. Heeyoung Lee, Associate Professor, Shibaura Institute of Technology

The researchers used Rayleigh scattering to calculate the modulation amplitude. Rayleigh scattering occurs when light interacts with particles smaller than its wavelength.

They obtained high-frequency resolution and estimated the modulation amplitude of the light regardless of the optical fiber's length by examining the spectrum width of noise caused by Rayleigh scattering. This novel approach, which measures Rayleigh noise components solely using the BOCDR setup and an electrical spectrum analyzer, is simple to use and improves process ease.

Aging and seismic damage to civil infrastructure present significant societal challenges. Optical fiber sensing technology offers a promising solution for monitoring the structural integrity of these infrastructures. By embedding long optical fibers within a structure, it is possible to detect strain and temperature distributions along the fibers.

Dr. Heeyoung Lee, Associate Professor, Shibaura Institute of Technology

Dr. Lee remarked, “Using Brillouin scattering to sense distributed strain and temperature provides highly sensitive and stable data. Our new method eliminates the need for additional devices, simplifying the process and reducing costs.”

The strategy used by the research team should progress the use of BOCDR in monitoring and guaranteeing the dependability and safety of vital infrastructure.

Journal Reference:

Kikuchi, K., et al. (2024) Accurate estimation of modulation amplitude in Brillouin optical correlation-domain reflectometry based on Rayleigh noise spectrum. Scientific Reports. doi.org/10.1038/s41598-024-56426-2