Fabrication of Optical Fiber and Fiber Amplifiers: From Design to Applications

Dear Colleagues,

The earliest development stage of optical fibers benefited from peoples’ pursuit of high-capacity communication. Apart from light transmission, optical fibers can also be utilized in sensing, filtering, amplification, and lasering. Different applications have incubated innovation in materials, structures, and fabrication methods of optical fibers. In terms of materials, substrates (such as silica and soft silica), polymers, and dopants (such as erbium, ytterbium, fluorine, and bismuth) are utilized to manufacture optical fibers with different functions. As for the structures, in addition to the traditional double-layered core-cladding fiber structure, multi-layered, multi-core, and micro-structured optical fibers are also developed. The fabrication of optical fibers involves methods such as vapor deposition methods, microtapering, and even 3D printing. Moreover, a combination of different materials, structures, and fabrication methods has led to the innovation and improvement of various functional fiber optic devices, such as FBGs and fiber interferometers. More materials, structures, and fabrication methods can be developed and improved to meet the new requirements of different applications.

Fiber amplifiers comprise an important branch of fiber optic devices. There are two main categories of fiber amplifiers: rare-earth-doped fiber amplifiers (such as erbium-doped fiber amplifiers (EDFAs)) and nonlinear fiber amplifiers (such as fiber Raman amplifiers and fiber Brillouin amplifiers). EDFAs are widely used in wavelength division multiplexing (WDM) and dense wavelength division multiplexing (DWDM) systems. Larger capacity communication systems pose new demands for fiber amplifiers. For example, mode division multiplexing (MDM) and space division multiplexing (SDM) systems require few high-performance mode EDFAs and multi-core EDFAs. EDFAs mainly operate in the C-band and L-band. In order to expand the wavelength band and further improve the communication capacity, other rare-earth-doped fiber amplifiers (such as bismuth-doped fiber amplifiers), fiber Raman amplifiers, and fiber Brillouin amplifiers also need to be studied and improved.

This Special Issue on “Fabrication of Optical Fiber and Fiber Amplifier: From Design to Applications” will welcome basic, methodological, and cutting-edge research contributions, as regular and review papers that focus on:

• The development and improvement of materials, and design and fabrication methods for optical fibers;
• Specialty optical fibers, such as micro-structured optical fibers and polymer fibers;
• Special erbium-doped fiber amplifiers (EDFAs), such as few-mode EDFAs and multicore EDFAs;
• Other rare-earth-doped fiber amplifiers, such as bismuth-doped fiber amplifiers;
• Nonlinear fiber amplifiers, including fiber Raman amplifiers and fiber Brillouin amplifiers;
• Applications based on optical fibers and fiber amplifiers, such as optical fiber sensors and optical fiber lasers.

Dr. Shiying Xiao
Dr. Beilei Wu
Dr. Yudong Lian
Guest Editors

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• optical fibers
• specialty optical fibers
• optical fiber amplifiers
• EDFAs
• rare-earth-doped fiber amplifiers
• fiber Raman amplifiers
• fiber Brillouin amplifiers
• optical fiber sensors
• optical fiber lasers

Title: Adaptive denoising of fiber optic sensing heartbeat signals using combined DWT and NLM methods
Authors: Zixuan Peng, Kaimin Yu, Yuanfang Zhang，Peibin Zhu, Wen Chen, Jianzhong Hao
Affiliation: 1School of Ocean Information Engineering, Jimei University, Xiamen 361021, China 2School of Marine Equipment and Mechanical Engineering, Jimei University, Xiamen 361021, China 3Institute for Infocomm Research (I2R), Agency for Science, Technology and Research (A*STAR), Singapore 138632, Singapore
Abstract: Multimode fiber optic micro-vibration sensing technology has emerged as a critical tool in diagnosing cardiovascular diseases by effectively monitoring heartbeat, respiration, and prolonged sleep quality signals in real-time. However, the presence of various noise sources poses a significant challenge to accurately analyzing and diagnosing these signals. While numerous denoising methods have been developed, they often struggle to adapt to changing signal characteristics and complex noise distributions. In this paper, we introduce an innovative denoising approach that combines adaptive Discrete Wavelet Transform (DWT) and Non-Local Mean (NLM) techniques. This method dynamically adjusts filtering parameters based on the autocorrelation characteristics of the denoised signal to achieve optimal denoising outcomes. Extensive testing using diverse ECG signals from multiple databases, each contaminated with additive Gaussian white noise (AWG) at varying signal-to-noise ratios (SNR), demonstrates the efficacy of our method. Comparative analyses against other denoising techniques, such as adaptive wavelet transform, NLM, and non-adaptive DWT combined with NLM, reveal that our proposed method outperforms existing state-of-the-art noise reduction approaches. Notably, our method enhances the output SNR by up to 3.1 dB compared to the latest non-adaptive DWT combined with NLM method. Additionally, denoising results of heartbeat signals obtained through multimode fiber micro-vibration sensing showcase the superior visual denoising capabilities of our approach over current methods. A key contribution of this study is the ability to achieve optimal denoising results without relying on original signals or precise noise evaluations. This adaptability enhances the practicality of the combined DWT and NLM approach, ultimately improving the accuracy of multimode fiber optic micro-vibration sensing for monitoring and diagnosing cardiovascular diseases.