Yosuke Mizuno

Yokohama National University · College of Engineering Science

Multimode fiber (MMF) sensors have been extensively developed and utilized in various sensing applications for decades. Traditionally, the performance of MMF sensors was improved by conventional methods that focused on structural design and specialty fibers. However, in recent years, the blossom of machine learning techniques has opened up new aven...

We implement a single-end-access reflectometric configuration for tactile sensing, incorporating a fiber Bragg grating (FBG) inscribed in a polymer optical fiber (POF). The folded architecture of the single-mode-multimode-single-mode structure effectively mitigates the generation of interference patterns, which are commonly induced by multimodal in...

We develop a new configuration of distributed strain and temperature sensing technology called double-slope-assisted Brillouin optical correlation-domain reflectometry. Its loss-independent operation is demonstrated through simplified simulation and proof-of-concept experiments using a standard silica single-mode fiber.

Brillouin optical correlation-domain analysis (BOCDA) utilizing low-coherence light sources offers high-resolution distributed strain and temperature sensing. However, conventional BOCDA requires dual-end injection of pump and probe light into the sensing fiber. To overcome this limitation, low-coherence Brillouin optical correlation-domain reflect...

We investigate the spatial resolution of direct-modulation Brillouin optical correlation-domain reflectometry (BOCDR) by exploring the impact of modulation amplitude and frequency. Our findings reveal that optimal resolution improvement is attained through an initial increase in modulation amplitude, followed by modulation frequency adjustment. The...

Abstract Fibre‐optic distributed Brillouin sensing that utilises correlation‐domain techniques often requires an optical delay fibre in the reference path to control the correlation peak order in the sensing fibre. Nonetheless, a suboptimal delay fibre length can result in decreased performance. In this work, as a first step towards clarifying the...

We demonstrate that fiber Bragg gratings in polymer optical fibers can lead to reflection peaks in any wavelength range when exciting high-order propagation modes, which can enhance the design of sensing systems for specific applications.

We present a new approach for measuring fiber tip temperature using low-coherence Brillouin optical correlation-domain reflectometry, which eliminates the need for an independent reference path and does not entail specific processing of the fiber tip.

We extend the measurement range of optical correlation-domain reflectometry (OCDR) by modulating the laser output frequency at two frequencies, while preserving spatial resolution. We demonstrate distributed reflectivity sensing with a ten-fold extended measurement range.

A simple, inexpensive, and high-sensitivity temperature and strain sensor based on a single-mode--multimode--single-mode (SMS) structure with core offset is developed and experimentally characterized. This sensor does not require specialty fibers and can be fabricated using a standard fiber fusion splicer. The dependencies of the temperature and st...

We present a method for measuring the transmission loss of an optical fiber using simplified optical correlation-domain reflectometry. By intentionally lowering the spatial resolution of the system, we observe the Rayleigh scattered signal for the first time without the need for a frequency shifter. Using this method, we simultaneously measure the...

The spatial resolution of direct-modulation Brillouin optical correlation-domain reflectometry is studied with respect to modulation amplitude and frequency. Results suggest that optimal resolution improvement is achieved by increasing modulation amplitude first, followed by frequency.

We show that the systematic error unique to Brillouin optical correlation-domain reflectometry (BOCDR) can be effectively suppressed by use of low-coherence light, and demonstrate distributed strain measurement with ~3 cm spatial resolution.

Compressed sensing (CS) is proposed in Brillouin optical correlation-domain reflectometry (BOCDR) to enhance the effective repetition rate at any single position along an optical fiber. Through the random selection of modulation frequencies applied to the laser source in each epoch that the entire fiber is traversed and the reconstruction of the un...

We present a method for measuring the transmission loss of an optical fiber using simplified optical correlation-domain reflectometry. By intentionally lowering the spatial resolution of the system, we observe the Rayleigh scattered signal for the first time without the need for a frequency shifter. Using this method, we simultaneously measure the...

In simplified optical correlation-domain reflectometry (OCDR) without the use of an electrical spectrum analyzer (ESA), the noise floor of the reflectivity distribution is distorted in long-range measurement, which sometimes causes significant errors in the distributed reflectivity measurement. Herein, we experimentally analyze the distorted noise...

A cost-effective method for estimating the Brillouin frequency shift (BFS) of the whole sensing fiber without using an electrical spectrum analyzer is developed. The Brillouin gain spectrum is down-converted and low-pass-filtered, and its total transmitted power is used to estimate the BFS. The strain dynamic range of this method is experimentally...

In this paper, a fiber-optic sensor based on Brillouin optical correlation-domain reflectometry (BOCDR) with a high repetition rate and real-time signal processing function is demonstrated with the assistance of swallow neural networks (NNs) constituted of no more than three hidden layers. In the proposed scheme, the signal processing time for ever...

Modal interference in a multimode fiber (MMF) has been utilized to develop simple sensors for various physical parameters. Herein, first, we investigate the dependencies of the core diameter and the numerical aperture (NA) of the MMF on the performance of multimode-interference-based strain and temperature sensing. We find that larger core diameter...

We characterize fiber gratings inscribed line-by-line in perfluorinated graded-index polymer optical fibers (PFGI-POFs) for tactile sensing. First, we measure the dependence of the wideband transmitted light spectrum on the distance between the fiber grating and an object composed of metal or rubber, clarifying that the spectral power is significan...

A simple, stable, and high-sensitivity temperature sensor based on multimode interference (MMI) in a polymer optical fiber (POF) with higher-order mode excitation has been developed. In a single-mode--multimode--single-mode (SMS) structure, one end of the multimode POF with physical-contact (PC) connectors is connected to a silica single-mode fiber...

We propose a newly configured optical correlation-domain reflectometry (OCDR) without the use of an electrical spectrum analyzer (ESA) for high-speed distributed reflectivity measurement with an enhanced spatial resolution. First, the operation of ESA-free OCDR is analyzed by numerical simulation, the results of which show the potential of the conf...

We propose a new scheme for polarization-sensitive distributed fiber-optic sensing, called polarization optical correlation-domain reflectometry (POCDR), and experimentally demonstrate its fundamental operations. In this scheme, the states of polarization (SOPs) of reference lights are controlled so that they are uniformly distributed on the Poinca...

Optical correlation-domain reflectometry (OCDR), which is known as one of the fiber-optic techniques for distributed reflectivity sensing, conventionally included an acousto-optic modulator, a reference path, and erbium-doped fiber amplifiers in its setup. In this work, by removing all of these components simultaneously, we develop a super-simplifi...

Various types of fiber-optic temperature sensors have been developed on the basis of modal interference in multimode fibers, which include not only glass fibers but also polymer optical fibers (POFs). Herein, we investigate the spectral patterns of the modal interference in multi-core POFs (originally developed for imaging) and observe their unique...

A strain-insensitive high-sensitivity temperature sensor based on multimode interference in a specialty fiber with a square core is developed and experimentally investigated. A 25-cm-long square-core fiber is used as a multimode fiber (MMF) of a single-mode--multimode--single-mode structure and the temperature dependence of its transmitted spectrum...

A strain-insensitive temperature sensor based on multimode interference using standard multimode fibers (MMFs) is proposed according to the comprehensive study of the characteristics of the MMFs. The temperature and strain dependences on the core diameter, numerical aperture (NA), and the length of the MMF section in the single-mode--multimode--sin...

Brillouin optical correlation-domain sensing enables high-speed Brillouin gain spectrum (BGS) measurement at random positions along the optical fiber. To extract the Brillouin frequency shift (BFS) that reflects the real-time strain information, machine learning methods of principal components analysis (PCA) and support vector machine (SVM) are use...

Brillouin optical correlation-domain reflectometry (BOCDR) is known as one of the distributed fiber-optic strain/temperature sensing techniques. Recently, a high-speed BOCDR configuration with no measurable strain limit has been developed, but only a sampling rate of 50 Hz has been experimentally demonstrated, limited by the use of a commercial mic...

Optical fibers have been used massively in communications, specifically silica fibers for long‐distance communications and polymer optical fibers (POFs) for household use. Despite their numerous advantages, the use of optical fibers with high power signals can result in their permanent damage. In recent years, researchers have been studying this un...

A variety of fiber-optic temperature sensors based on inline Mach–Zehnder interferometry (MZI) have been implemented for their ease of fabrication and cost efficiency, but it is difficult to control the length of the sensing area (i.e. the fiber section with sensitivity). Herein, we develop a new temperature sensor based on inline MZI by connecting...

We experimentally analyze the distorted noise floor peculiar to the kilometer-order range distributed reflectivity measurement by high-speed optical correlation-domain reflectometry. We also show that this noise floor can be compensated by appropriate filtering.

We propose a new scheme for polarization-sensitive distributed fiber-optic sensing, termed as polarization optical correlation-domain reflectometry (POCDR). We experimentally demonstrate its fundamental operations by measuring full states of polarization.

This article presents a review of the fuse effect in polymer optical fibers (POFs) and its sensing applications. First, the propagation mechanisms and the characteristics of the POF fuse are discussed, showing that its optical threshold power and propagation velocity are much lower than those of silica fiber fuse. In addition, it is shown that the...

The general neural networks (NNs) based on classification convert the Brillouin frequency shift (BFS) extraction in Brillouin-based distributed sensing to a problem in which the possible BFS output of the sensing system belongs to a finite number of discrete values. In this paper, we demonstrate a method of applying NNs with adaptive BFS incrementa...

Light detection and ranging (LiDAR) technology has recently been attracting considerable attention, but it is still difficult to achieve distributed reflectivity sensing and vibration detection simultaneously at high speed. To tackle this issue, we develop a new LiDAR configuration by extending fiber-optic correlation-domain reflectometry to the sp...

Brillouin optical correlation-domain reflectometry (BOCDR) is a fiber-optic distributed sensing technique with single-end accessibility and high spatial resolution. In BOCDR, the measured Brillouin gain spectrum (BGS) distribution is generally given by a convolution of the intrinsic BGS distribution and the beat-power spectrum. In most conventional...

Aging degradation and seismic damage of civil infrastructures have become a serious issue for society, and one promising technology for monitoring their conditions is optical fiber sensing. Glass optical fibers have been predominantly used for the past several decades to develop fiber sensors, but currently polymer or plastic optical fibers (POFs)...

In standard single-end-access Brillouin optical correlation-domain reflectometry (BOCDR), the systematic error caused by the phase difference between amplitude modulation (AM) and frequency modulation (FM) in the light source can be up to tens of megahertz, causing considerable errors in strain and temperature measurement. In this letter, we develo...

We put forward a new theory on Brillouin optical correlation-domain reflectometry (BOCDR) based on arbitrary waveform modulation. We derive a universal representation for the spatial resolution using the foot convexity of the beat spectrum. This result well explains the previous results based on sinusoidal modulation, and thus our theory is the con...

We develop a new concept of two-end-access Brillouin optical correlation-domain reflectometry and numerically show its effectiveness on compensation of the systematic measurement error caused by the phase delay between amplitude and frequency modulations.

We analyze the operation of Brillouin optical correlation-domain reflectometry based on arbitrary-waveform modulation of optical frequency. We provide a general expression for spatial resolution, which is proportional to the foot convexity of the beat-power spectrum.

We show that 1-°C drift of laser temperature yields strain error of ~8 με in Brillouin optical correlation-domain reflectometry. We do not require laser thermal control, leading to cost reduction and downsizing of the system.

We demonstrate distributed measurement of the polarization beat length along single-mode optical fibers (SMFs) using slope-assisted Brillouin optical correlation-domain reflectometry (BOCDR) with high spatial resolution, long measurement range, high sampling rate, and single-end accessibility. The beat lengths of SMFs wound on mandrels with radii o...

Fiber‐optic sensing is resistant to electromagnetic interference; therefore, electromagnetic field sensing using fiber‐optic sensors is challenging. Herein, the first demonstration of fiber‐optic intrinsic electromagnetic field sensing based on modal interferometry with the highest reported sensitivity is presented (here, to be intrinsic means that...

Brillouin optical correlation-domain reflectometry (BOCDR) is one of the fiber-optic Brillouin-based distributed sensing techniques for strain and temperature with single-end accessibility. Since the first proposal of the basic concept in 2008, the performance of BOCDR has been drastically improved from a variety of aspects including high-speed ope...

Brillouin optical correlation-domain reflectometry (BOCDR) generally suffers from the trade-off relationship between the spatial resolution and the measurement range. In this work, we perform a proof-of-concept demonstration of a chirp modulation scheme to extend the measurement range of BOCDR. In this scheme, optical frequency is modulated using a...

This feature issue of Optics Express contains 17 articles expanding on recent advances in optical sensors presented at the eighth Asia-Pacific Optical Sensors Conference (APOS 2019) held in Auckland, New Zealand, from November 19 to 22, 2019. These articles span sensing for real-time positioning, refractive indices, strain, gas, and temperature usi...

To achieve high torque density and high power density of rotary ultrasonic motors (USMs), in this article, we develop a rod-shaped transducer operating in torsional/bending (T/B) modes and excite two elliptical motions on its bilateral ends to drive the rotor orthogonally pressed onto the transducer. Here, the torsional vibration, the driving struc...

We present a method for generating cascaded forward Brillouin scattering (CFBS) on the basis of a counter-propagated pump-probe technique with backward stimulated Brillouin scattering used as its seed. The CFBS, induced by forward stimulated Brillouin scattering (FSBS), is generated via the energy transfer from the probe light to other acoustic res...

We present the first report on reflectometric optical fiber sensing based on mechanically induced cascaded long-period grating (LPG) structure. This method utilizes in-house designed mechanical casings and a bare fiber. When a fiber is sandwiched between the casings and pressed by tightening screws, an LPG is induced due to a photo-elastic effect....

We show that 1 °C drift of laser temperature yields a strain error of ∼8 με in Brillouin optical correlation-domain reflectometry. Under the assumption that the strain measurement accuracy is +/–20 με (severe requirement), +/–2.5 °C drift of the laser temperature can be permitted for proper system operation. We prove this prediction by performing d...

To enhance the torque and output power of rod-shaped piezoelectric rotary motors, in this study, we employ alumina to substitute the metal parts of transducers considering that the high Young's modulus of alumina may avoid preload-induced vibration reduction and enable the transducers to generate high driving force. Besides, alumina exhibits a rela...

Slope-assisted Brillouin optical correlation-domain reflectometry (SA-BOCDR) is one of the high-speed distributed strain sensing techniques, but its strain dynamic range has been limited to approximately 0.15%, which is far from being sufficient for some practical applications. In this paper, we clarify that, unlike widely used time-domain techniqu...

Brillouin optical correlation‐domain reflectometry (BOCDR) is one of the fibre‐optic distributed strain and temperature sensing systems. Conventionally, BOCDR has been implemented using three erbium‐doped fibre amplifiers (EDFAs) to enhance the signal‐to‐noise ratio (SNR) of the measurement. However, the use of multiple EDFAs has restricted the siz...

We develop a new noise suppression technique to perform distributed strain and temperature sensing based on a higher-speed configuration of Brillouin optical correlation-domain reflectometry even when a polymer optical fiber (POF) is used as a sensing fiber. We acquire the spectral difference between with and without reference light, leading to sel...

We observe multimodal interference in single-mode-multimode-single-mode sensors comprising short polymer optical fibers (POFs) with lengths from 100 mm down to 7 mm. Characteristic spectral peaks/dips are observed not in the conventionally used telecom band but around 1000 nm. We find that the dip wavelength depends on temperature but that the sens...