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JOURNAL OF LIGHTWAVE TECHNOLOGY, VOL. 35, NO. 11, JUNE 1, 2017

Slope-Assisted Brillouin Optical Correlation-Domain
Reflectometry Using Polymer Optical Fibers With
High Propagation Loss
Heeyoung Lee, Neisei Hayashi, Yosuke Mizuno, Member, IEEE, and Kentaro Nakamura, Member, IEEE

Abstract—We have recently developed slope-assisted Brillouin
optical correlation-domain reflectometry (SA-BOCDR) for higher
speed distributed measurement of strain and temperature. However, no reports have been published yet on the use of high-loss
fibers. Here, we implement SA-BOCDR using a high-loss polymer
optical fiber (POF) for the first time. Due to the gradual reduction in the transmitted power along the POF, the measurement
sensitivities are found to depend on sensing position. This uniqueeffect is investigated experimentally, and then a correct POF-based
distributed measurement is performed by compensating this effect.
Index Terms—Brillouin scattering, distributed measurement,
optical fiber sensors, polymer optical fibers.

I. INTRODUCTION
IBER-OPTIC distributed sensing based on Brillouin scattering [1] has been regarded as one of the most important techniques to detect damages of civil infrastructures. A
variety of its configurations developed so far can be classified
into five categories: Brillouin optical time-domain reflectometry(BOTDR) [2]–[5], Brillouin optical correlation-domain reflectometry (BOCDR) [6]–[15], Brillouin optical time-domain analysis (BOTDA) [16]–[21], Brillouin optical frequency-domain
analysis (BOFDA) [22]–[24], and Brillouin optical correlationdomain analysis (BOCDA) [25]–[29]. Each configuration, with
its own advantages and disadvantages, has been extensively
studied to enhance the performance. Here, among them, we
focus on BOCDR, which is the only technique that can simultaneously achieve intrinsically single-end accessibility and highspatial resolution.
Since the first proposal of BOCDR [6], a number of schemes
have been implemented to improve its performance, such as
the measurement range [7], [8], spatial resolution [9], [10], andF

Manuscript received November 25, 2016; revised January 23, 2017; accepted
January 26, 2017. Date of publication February 1, 2017; date of current version
April 20, 2017. This work was supported in part by the JSPS KAKENHI
Grants 25709032, 26630180, and 25007652, and in part by research grants
from the Japan Gas Association, the ESPEC Foundation for Global Environment
Research and Technology, and the Association for Disaster Prevention Research.
H. Lee, Y. Mizuno, and K. Nakamura are with the Institute of Innovative
Research, Tokyo Institute of Technology, Yokohama 226-8503, Japan (e-mail:hylee@sonic.pi.titech.ac.jp; ymizuno@sonic.pi.titech.ac.jp; knakamur@sonic.
pi.titech.ac.jp).
N. Hayashi is with the Research Center for Advanced Science and Technology, The University of Tokyo, Tokyo 153-8503, Japan (e-mail: hayashi@
cntp.t.u-tokyo.ac.jp).
Color versions of one or more of the figures in this paper are available online
at http://ieeexplore.ieee.org.
Digital Object Identifier 10.1109/JLT.2017.2663440

sampling rate [11]. One of the newly developed configurations
is slope-assisted (SA-) BOCDR [12], which uses the powerof the Brillouin gain spectrum (BGS) to derive the Brillouinfrequency shift (BFS), leading to a high sampling rate, losspoint detectability, and beyond-nominal resolution effect [13].
Its fundamental operation has been well investigated when lowloss silica glass fibers are used as fibers under test (FUTs) [12],but no reports have been provided on how the performanceis affected by use of high-loss FUTs, including tellurite glass
fibers [9], chalcogenide fibers [30], and polymer optical fibers(POFs) [14], [15]. At the sacrifice of the shortened measurement
range, the use of such high-loss fibers provides BOCDR withsome advantages, such as stronger Brillouin signals (for tellurite[9] and chalcogenide fibers [30]) (leading to enhanced spatial
resolution), extended upper limit of detectable strain [14] andmuch higher temperature sensitivity [15] (for POFs). Thus, it isof crucial importance to investigate the influence of the use ofhigh-loss fibers on SA-BOCDR operation.
In this work, employing POFs as high-loss fibers, we demonstrate high-speed distributed sensing based on SA-BOCDR. We
show that, in contrast to the case of low-loss silica fibers, thestrain and temperature sensitivities are dependent on sensing
position because the transmitted power is gradually reducedin the POFs. After analyzing this unique effect experimentally,
we show that this effect can be compensated so that a correct
POF-based distributed measurement using SA-BOCDR can be
performed.
II. PRINCIPLESWhen light propagates in an optical fiber, due to the interaction with acoustic phonons, backscattered Stokes light is generated through Brillouin scattering. The central frequency of
the Stokes light spectrum (i.e., BGS) is lowered than that of
the incident light spectrum. This central frequency downshift isreferred to as BFS, which is about ∼10.8 GHz for silica singlemode fibers (SMFs) [1] and ∼2.8 GHz for perfluorinated POFs
[14] when the incident light wavelength is 1550 nm. When strain
or temperature change is applied to the fiber, the BFS shifts tohigher or lower frequency depending on the fiber types. Theirstrain- and temperature-dependence coefficients are reported tobe approximately 500 MHz/% and 1 MHz/K for silica SMFs
[31], [32] and –120 MHz/% and –3 MHz/K for POFs [15],[32]. These dependences have been widely exploited as a basic

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LEE et al.: SLOPE-ASSISTED BRILLOUIN OPTICAL CORRELATION-DOMAIN REFLECTOMETRY USING POLYMER OPTICAL FIBERS

Fig. 1. (a) Schematic of the operating principle of SA-BOCDR. (b) and(c) Power and power-change distributions along (b) a low-loss fiber and (c)a high-loss fiber; with (solid curves) and without (dotted lines) partial strain andheat.

sensing mechanism of fiber-optic distributed Brillouin sensors,
including BOCDR.
BOCDR enables distributed measurement using a so-called
correlation peak inside the FUT [6], [10], [33]. The correlation
peak can be generated by sinusoidally modulating the output frequency of the laser; the position of the correlation peak can bescanned along the FUT by sweeping the modulation frequency
fm . In general, due to the nature of sinusoidal frequency modulation, multiple correlation peaks are periodically generated
along the FUT, which limits the measurement range dm as [10]
dm =

c
,
2nfm

(1)

where c is the velocity of light in vacuum and n is the corerefractive index. The spatial resolution Δz is given by [10]
Δz =

c ΔνB
,
2 π n fm Δf(2)

where ΔνB is the Brillouin bandwidth and Δf is the modulation
amplitude. Note that Eq. (2) holds true only when fm is lower
than ΔνB [10].
Standard BOCDR acquires the whole BGS to derive the BFS
at a single sensing position (as a peak frequency of the BGS)
[6], [10] which is relatively time-consuming. In contrast, SABOCDR operates based on the spectral power change at a fixed
frequency vB 0 by exploiting its one-to-one correspondence tothe BFS (see Fig. 1(a)) [12], which enables high-speed measurement. Note that the BFS of the FUT needs to be mea-

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sured beforehand in SA-BOCDR to optimize the measurement
sensitivity and/or dynamic range. One unique feature of SABOCDR is that its final output (i.e., a power-change distribution
along the FUT) does not directly reproduce the actual BFS
distribution, while the output of standard BOCDR completely
reproduces it. As described in detail in [13], the power-change
distribution in SA-BOCDR basically shows a trapezoidal shape,and only when the length of strained or heated section is equal
to the theoretical spatial resolution, it shows a triangular shape.
In addition, SA-BOCDR has a unique ability to detect strainedor heated sections even shorter than the nominal resolution calculated by Eq. (2) [13].
When a silica SMF with a low propagation loss is used as
an FUT, unless the FUT is extremely long, the Brillouin powershows almost no change irrespective of the sensing position (seeFig. 1(b)). However, when a relatively high-loss fiber is used,even when the FUT is short, the Brillouin power decreases withincreasing distance from the proximal end of the FUT (i.e.,
the pigtail end of the second port of a circulator) as shown in
Fig. 1(c). Note that the final system output of SA-BOCDR isprovided as a power-change distribution, and strain (or heat) is
displayed as a positive shift in the vertical axis. The weakeningof the BGS along the high-loss fiber leads to the reduction in
the spectral slope, finally resulting in the gradual decrease in thestrain and temperature sensitivities.
III. EXPERIMENTAL SETUP
We employed a 15.0-m-long perfluorinated graded-index
POF as an FUT. The POF had a three-layered structure consisting of core, cladding, and overcladding (diameters: 50, 70,
and 490 μm, respectively). A propagation loss of the POF was∼250 dB/km at 1550 nm.
The experimental setup of POF-based SA-BOCDR (refer toFig. 3 in [12]) is basically the same as that of standard BOCDR[6] except for the electrical signal processing. All the light paths
except the FUT are composed of silica SMFs. As a light source,a laser diode at 1550 nm with a bandwidth of ∼1 MHz wasused. Its output was divided into two light beams: pump andreference. The pump light was amplified to ∼25 dBm using
an erbium-doped fiber amplifier (EDFA) and injected into the
FUT. The backscattered Stokes light was amplified to ∼1 dBm
using another EDFA. The reference light was guided through a∼1-km-long delay fiber, amplified to ∼2 dBm, and then coupledwith the Stokes light for heterodyne detection. Using a polarization controller, the polarization state was adjusted so that thesignal-to-noise ratio (SNR) became maximal for each measurement (note that the use of a polarization scrambler for observing
Brillouin signals in POFs causes considerable reduction in SNR[34]). The optical beat signals were converted into electricalsignals using a photo diode and observed using an electrical
spectrum analyzer (ESA).
Subsequently, exploiting the narrow band-pass filtering function of the ESA (video bandwidth: 10 kHz; resolution bandwidth: 10 MHz), the change in the spectral power at vB 0 was
sequentially output to an oscilloscope (OSC). As a preparatory
experiment for determining the vB 0 value and the bandwidth of

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JOURNAL OF LIGHTWAVE TECHNOLOGY, VOL. 35, NO. 11, JUNE 1, 2017

Fig. 3.
Fig. 2.

BGS distribution along the POF.

Local BGS obtained at 1.0 m away from the proximal POF end.

the linear region, we measured the local BGS obtained at 1.0 m
away from the proximal POF end (see Fig. 2). The detailed
measurement conditions are described in the next paragraph.
The BFS was 2.76 GHz at room temperature (25 °C). The optimal vB 0 value was found to be 2.80 GHz, which was set to ahigher frequency than the BFS because the BGS shifts to lower
frequency in POFs with strain and/or heating [15] (unlike thecase of silica-SMF-based SA-BOCDR). The bandwidth of thelinear region (refer to [12] for its definition) was approximately
140 MHz (2.80–2.94 GHz), which corresponds to the strain of
up to ∼1.15% and the temperature change of ∼43 °C in the POF(with light propagation, the BGS is basically weakened in thevertical direction; in other words, if normalized, the BGS shows
an only negligible change depending on the location, leading
to almost no position dependence of the linear range). Here we
discuss the shape of the BGS, which is neither Lorentzian nor
symmetrical. Compared to silica fibers, POFs inherently have amuch wider Brillouin bandwidth (>100 MHz) [14]. Moreover,in general, as the modulation amplitude grows higher, the Brillouin bandwidth becomes wider [10], which deviates the BGS
from a Lorentzian shape. Meanwhile, the asymmetric shapeoriginates from the overlap of the foot of the Rayleigh spectrum[34], which also grows wider by modulation in the same manneras the BGS [10]. Note that the BFS of the POF (∼2.8 GHz) is∼4 times lower than that of silica fibers [14] and that the BGS
is more likely to be overlapped by the Rayleigh spectrum.
In the preceding measurement as well as in the following experiments, the modulation frequency fm and amplitude Δf were
set to 6.15–6.33 MHz and 0.6 GHz, respectively, corresponding
to the measurement range of 18.1 m and the theoretical spatial
resolution of 0.96 m according to (1) and (2). The repetition rate
was set to 100 Hz, and averaging was performed 128 times on
the OSC to improve the SNR.
IV. EXPERIMENTAL RESULTSFirst, to derive the theoretical strain and temperature sensitivities as functions of sensing position, we measured the BGS
distribution along the POF with a constant interval of 1.0 m using standard BOCDR (see Fig. 3). Due to the high propagation
loss in the POF, the peak power of the BGS gradually decreased
with light propagation, which also induced the reduction in its
spectral slope. Note that the BGS is weakened even within thefiber length of the spatial resolution, resulting an unavoidable
measurement error. Here we interpreted the measured sensitivity
as that of the midpoint of the corresponding fiber section.
By differentiating the spectral slope in the linear range(vB 0 = 2.80−2.94 GHz, the theoretical dependence of the sensitivity on sensing position was derived (see Fig. 4(a)). The slope
decreased almost linearly as the sensing position became far
from the proximal POF end with a coefficient of approximately–0.16 dB/GHz/m, which corresponds to the strain sensitivity
dependence of –1.99 × 10–2 dB/%/m and the temperature sensitivity dependence of –5.22 × 10–4 dB/ °C/m. Subsequently,
we measured the spectral power dependence on sensing position when the temperature of the POF was locally changed to
60 °C. The spectral powers were measured when 1.0-m-longsections (4 sections; 2.0–3.0, 5.0–6.0, 8.0–9.0, 11.0–12.0 m
distant from the proximal POF end) were heated, and plotted as functions of temperature (see Fig. 4(b)). The measured
data were in good agreement with the theoretical trends (indicated by dotted lines) obtained from the BGS distributions (seeFig. 3). The spectral powers were almost linearly dependent
on temperature, and their coefficients were found to decrease
with increasing distance from the proximal POF end. For eachsection, the temperature sensitivity was calculated and plotted
as a function of sensing position (see Fig. 4(c)). The dependence coefficient was −4.98 × 10−4 dB/◦ C/m (corresponding
to −2.10 × 10−2 dB/%/m for strain), which is in good agreement with the theoretical value calculated from the BGS distribution (−5.22 × 10−4 dB/◦ C/m).
Finally, we demonstrated distributed measurement of strain
and temperature along the POF using SA-BOCDR. The structure of the FUT is depicted in Fig. 5(a). A 1.0-m-long section(close to the nominal spatial resolution) was strained for 1%,
and another 1.0-m-long section was heated to 60 °C. The measured power-change distribution is shown in Fig. 5(b). At the
expected sections, the power changes corresponding to the strain
and the temperature change were observed, which moderately
agrees with the theoretical dotted line considering the sensitivity dependence on sensing position and the trapezoidal effectof SA-BOCDR [13]. Thus, the applied strain and temperaturechange were correctly detected. The measurement errors originate from the signal fluctuations caused by the low SNR, which
can be improved by increasing the number of averaging, increasing the pump power, or optimizing the low-pass filteringfunction of the ESA.

LEE et al.: SLOPE-ASSISTED BRILLOUIN OPTICAL CORRELATION-DOMAIN REFLECTOMETRY USING POLYMER OPTICAL FIBERS

2309

Fig. 4. (a) Sensitivity plotted as a function of sensing position for theoretical analysis. The dotted line is a linear fit. (b) Spectral powers plotted as functions oftemperature; measured at four different sections in the POF. The dotted lines are theoretical trends. (c) Temperature sensitivity plotted as a function of sensing
position. The dotted line is a linear fit.

Fig. 5. (a) Structure of the fiber under test for final demonstration. (b) Powerchange distributions along the sensing fiber. The dotted line is a theoreticaltrend.

V. CONCLUSION
We investigated the performance of SA-BOCDR using a
POF with a relatively high propagation loss (∼250 dB/km
at 1550 nm). The measurement sensitivity was shown to be
dependent on the sensing position in the POF. The dependence coefficients were −2.10 × 10−2 dB/%/m for strain and−4.98 × 10−4 dB/◦ C/m for temperature, which agreed wellwith the theoretical predictions. By compensating this influence,
we successfully demonstrated a distributed strain and temperature measurement along the POF with a spatial resolution of∼1 m. We believe that these results will be an important archivein implementing SA-BOCDR using high-loss fibers, especially
POFs, for high-speed distributed strain and temperature sensing
with high flexibility and high temperature sensitivity.

REFERENCES[1] G. P. Agrawal, Nonlinear Fiber Optics. San Diego, CA, USA: Academic,
1995.
[2] T. Kurashima, T. Horiguchi, H. Izumita, S. Furukawa, and Y. Koyamada,“Brillouin optical-fiber time domain reflectometry,” IEICE Trans. Commun., vol. E76-B, no. 4, pp. 382–390, Apr. 1993.

[3] Q. Li, J. Gan, Y. Wu, Z. Zhang, J. Li, and Z. Yang, “High spatial resolution BOTDR based on differential Brillouin spectrum technique,” IEEE
Photon. Technol. Lett., vol. 28, no. 14, pp. 1493–1496, Jul. 2016.
[4] F. Wang, W. Zhan, X. Zhang, and Y. Lu, “Improvement of spatial resolution
for BOTDR by iterative subdivision method,” J. Lightw. Technol., vol. 31,
no. 23, pp. 3663–3667, Dec. 2013.
[5] D. Iida and F. Ito, “Detection sensitivity of Brillouin scattering near Fresnel
reflection in BOTDR measurement,” J. Lightw. Technol., vol. 26, no. 4,
pp. 417–424, Feb. 2008.
[6] Y. Mizuno, W. Zou, Z. He, and K. Hotate, “Proposal of Brillouin opticalcorrelation-domain reflectometry (BOCDR),” Opt. Exp., vol. 16, no. 16,
pp. 12148–12153, Aug. 2008.
[7] Y. Mizuno, Z. He, and K. Hotate, “Measurement range enlargement inBrillouin optical correlation-domain reflectometry based on temporal gating scheme,” Opt. Exp., vol. 17, no. 11, pp. 9040–9046, May 2009.
[8] Y. Mizuno, Z. He, and K. Hotate, “Measurement range enlargementin Brillouin optical correlation-domain reflectometry based on doublemodulation scheme,” Opt. Exp., vol. 18, no. 6, pp. 5926–5933, Mar. 2010.
[9] Y. Mizuno, Z. He, and K. Hotate, “Distributed strain measurement using
a tellurite glass fiber with Brillouin optical correlation-domain reflectometry,” Opt. Commun., vol. 283, no. 11, pp. 2438–2441, Feb. 2010.
[10] Y. Mizuno, W. Zou, Z. He, and K. Hotate, “Operation of Brillouin opticalcorrelation-domain reflectometry: Theoretical analysis and experimental
validation,” J. Lightw. Technol., vol. 28, no. 22, pp. 3300–3306, Nov.
2010.
[11] Y. Mizuno, N. Hayashi, H. Fukuda, K. Y. Song, and K. Nakamura,“Ultrahigh-speed distributed Brillouin reflectometry,” Light, Sci. Appl.,
vol. 5, Dec. 2016, Art. ID e16184.
[12] H. Lee, N. Hayashi, Y. Mizuno, and K. Nakamura, “Slope-assisted Brillouin optical correlation-domain reflectometry: Proof of concept,” IEEE
Photon. J., vol. 8, no. 3, Jun. 2016, Art. ID 6802807.
[13] H. Lee, N. Hayashi, Y. Mizuno, and K. Nakamura, “Operation of slopeassisted Brillouin optical correlation-domain reflectometry: Comparisonof system output with actual frequency shift distribution,” Opt. Exp.,
vol. 24, no. 25, pp. 29190–29197, Dec. 2016.
[14] Y. Mizuno and K. Nakamura, “Experimental study of Brillouin scatteringin perfluorinated polymer optical fiber at telecommunication wavelength,”Appl. Phys. Lett., vol. 97, no. 2, Jul. 2010, Art. ID 021103.
[15] Y. Mizuno and K. Nakamura, “Potential of Brillouin scattering in polymer
optical fiber for strain-insensitive high-accuracy temperature sensing,”
Opt. Lett., vol. 35, no. 23, pp. 3985–3987, Dec. 2010.
[16] T. Horiguchi and M. Tateda, “BOTDA-nondestructive measurement of
single-mode optical fiber attenuation characteristics using Brillouin interaction: Theory,” J. Lightw. Technol., vol. 7, no. 8, pp. 1170–1176, Aug.
1989.
[17] Y. Peled, A. Motil, L. Yaron, and M. Tur, “Slope-assisted fast distributed
sensing in optical fibers with arbitrary Brillouin profile,” Opt. Exp., vol. 19,
no. 21, pp. 19845–19854, Oct. 2011.
[18] Y. Dong et al., “High-spatial-resolution fast BOTDA for dynamic strain
measurement based on differential double-pulse and second-order sideband of modulation,” IEEE Photon. J., vol. 5, no. 3, Jun. 2013, Art. ID
2600407.
[19] M. A. Soto, S. L. Floch, and L. Thévenaz, “Bipolar optical pulse coding
for performance enhancement in BOTDA sensors,” Opt. Lett., vol. 21,
no. 14, pp. 16390–16397, Jul. 2013.

2310[20] R. Bernini, A. Minardo, and L. Zeni, “Dynamic strain measurement in
optical fibers by stimulated Brillouin scattering,” Opt. Lett., vol. 34, no. 17,
pp. 2613–2615, Sep. 2009.
[21] Y. Dong, P. Xu, H. Zhang, Z. Lu, L. Chen, and X. Bao, “Characterizationof evolution of mode coupling in a graded-index polymer optical fiber byusing Brillouin optical time-domain analysis,” Opt. Exp., vol. 22, no. 22,
pp. 26510–26516, Nov. 2014.
[22] D. Garus, K. Krebber, and F. Schliep, “Distributed sensing technique basedon Brillouin optical-fiber frequency-domain analysis,” Opt. Lett., vol. 21,
no. 17, pp. 1402–1404, Sep. 1996.
[23] A. Wosniok, Y. Mizuno, K. Krebber, and K. Nakamura, “L-BOFDA: A
new sensor technique for distributed Brillouin sensing,” in Proc. 5th Eur.
Workshop Opt. Fibre Sens., Krakow, Poland, 2013, vol. 8794, pp. 8794–
8798.
[24] R. Bernini, A. Minardo, and L. Zeni, “Dstributed sensing at centimeterscale spatial resolution by BOFDA: Measurements and signal processing,”
IEEE Photon. J., vol. 4, no. 1, pp. 48–56, Feb. 2012.
[25] K. Hotate and T. Hasegawa, “Measurement of Brillouin gain spectrum
distribution along an optical fiber using a correlation-based technique—Proposal, experiment and simulation,” IEICE Trans. Electron., vol. E83-C,
no. 3, pp. 405–412, Mar. 2000.
[26] Y. H. Kim, K. Lee, and K. Y. Song, “Brillouin optical correlation domain
analysis with more than 1 million effective sensing points based on differential measurement,” Opt. Exp., vol. 23, no. 26, pp. 33241–33248, Dec.
2015.
[27] W. Zou, C. Jin, and J. Chen, “Distributed strain sensing based on combination of Brillouin gain and loss effects in Brillouin optical correlation
domain analysis,” Appl. Phys. Exp., vol. 5, no. 8, Jul. 2012, Art. ID 082503.
[28] R. Cohen, Y. London, Y. Antman, and A. Zadok, “Brillouin optical correlation domain analysis with 4 millimeter resolution based on amplified
spontaneous emission,” Opt. Exp., vol. 22, no. 10, pp. 12070–12078, May
2014.
[29] J. H. Jeong, K. Lee, K. Y. Song, J. M. Jeong, and S. B. Lee, “Differential
measurement scheme for Brillouin optical correlation domain analysis,”
Opt. Exp., vol. 20, no. 24, pp. 27094–27101, Nov. 2012.
[30] K. S. Abedin, “Observation of strong stimulated Brillouin scatteringin single-mode As2Se3 chalcogenide fiber,” Opt. Exp., vol. 13, no. 25,
pp. 10266–10271, Dec. 2005.
[31] T. Horiguchi, T. Kurashima, and M. Tateda, “Tensile strain dependence ofBrillouin frequency shift in silica optical fibers,” IEEE Photon. Technol.
Lett., vol. 1, no. 5, pp. 107–108, May 1989.
[32] T. Kurashima, M. Tateda, and M. Tateda, “Thermal effects on the Brillouinfrequency shift in jacketed optical silica fibers,” Appl. Opt., vol. 29, no. 15,
pp. 2219–2222, May 1990.
[33] K. Hotate and Z. He, “Synthesis of optical-coherence function and its
applications in distributed and multiplexed optical sensing,” J. Lightw.
Technol., vol. 24, no. 7, pp. 2541–2557, Jul. 2006.
[34] Y. Mizuno, N. Hayashi, and K. Nakamura, “Polarisation state optimisationin observing Brillouin scattering signal in polymer optical fibres,” IEICEElectron. Lett., vol. 49, no. 1, pp. 56–57, Jan. 2013.

Heeyoung Lee was born in Seoul, South Korea, on August 21, 1990. She
received the B.E. degree in mechanical engineering from Kyungpook National
University, Daegu, South Korea, in 2014. Since 2015, she has been working
toward the M.E. degree in fiber-optic sensors at Tokyo Institute of Technology,
Tokyo, Japan.
Her research interests include fiber-optic sensing and polymer optics.
Ms. Lee is a Member of the Japanese Society of Applied Physics.

JOURNAL OF LIGHTWAVE TECHNOLOGY, VOL. 35, NO. 11, JUNE 1, 2017

Neisei Hayashi was born in Gunma, Japan, on April 13, 1988. He received the
B.E. degree in advanced production from Gunma National College of Technology, Maebashi, Japan, in 2011, and the M.E. and Dr. Eng degrees in information
processing from Tokyo Institute of Technology, Tokyo, Japan, in 2013 and 2015,
respectively.
From 2013 to 2015, he was involved in polymer fiber sensing for his Dr.
Eng. degree with Tokyo Institute of Technology. Also from 2013 to 2015, he
was a Research Fellow (DC1) of the Japan Society for the Promotion of Science (JSPS). Since 2016, he he has been continuing to study fiber sensing asa Research Fellow (PD) of JSPS with The University of Tokyo, Tokyo, Japan.
His research interests include fiber-optic sensing, polymer optics, and nonlinear
optics.
Mr. Hayashi recived the TELECOM System Technology Award for Student in 2012, the Seiichi Tejima Doctoral Dissertation Award in 2015, and the
NF Foundation R&D Encouragement Award in 2016. He is a Member of theJapanese Society of Applied Physics and the Institute of Electronics, Information, and Communication Engineers of Japan.

Yosuke Mizuno (M’14) was born in Hyogo, Japan, on October 13, 1982. Hereceived the B.E., M.E., and Dr. Eng. degrees in electronic engineering fromThe University of Tokyo, Tokyo, Japan, in 2005, 2007, and 2010, respectively.
From 2007 to 2010, he was involved in Brillouin optical correlation-domainreflectometry for his Dr. Eng. degree with The University of Tokyo. From 2007
to 2010, he was a Research Fellow (DC1) of the Japan Society for the Promotionof Science. From 2010 to 2012, as a Research Fellow (PD) of JSPS, he worked
on polymer optics with Tokyo Institute of Technology, Tokyo, Japan. In 2011,
he stayed with BAM Federal Institute for Materials Research and Testing, Germany, as a Visiting Research Associate. Since 2012, he has been an AssistantProfessor with the Precision and Intelligence Laboratory (currently, Instituteof Innovative Research), Tokyo Institute of Technology, where he is active infiber-optic sensing, polymer optics, and ultrasonics.
Dr. Mizuno received the Funai Research Award in 2010, the Ando Incentive
Prize for the Study of Electronics in 2011, the NF Foundation R&D Encouragement Award in 2012, the Tokyo Tech Challenging Research Award in 2013,
the Konica Minolta Imaging Science Award in 2014, the Japanese Society ofApplied Physics (JSAP) Young Scientist Presentation Award in 2015, and the
ESPEC Prize for the Encouragement of Environmental Studies in 2016. He isa Member of the IEEE Photonics Society, the JSAP, and the Institute of Electronics, Information, and Communication Engineers of Japan.

Kentaro Nakamura (M’00) was born in Tokyo, Japan, on July 3, 1963. Hereceived the B.E., M.E., and Dr. Eng. degrees from Tokyo Institute of Technology, Tokyo, Japan, in 1987, 1989, and 1992, respectively.
Since 2010, he has been a Professor with the Precision and Intelligence Laboratory (currently, Institute of Innovative Research), Tokyo Institute of Technology. His research interets include applications of ultrasonic waves, measurementof vibration and sound using optical methods, and fiber-optic sensing.
Prof. Nakamura received the Awaya Kiyoshi Award for encouragement ofresearch from the Acoustical Society of Japan (ASJ) in 1996, and the Best Paper Awards from the Institute of Electronics, Information and Communication
Engineers (IEICE) in 1998 and from the Symposium on Ultrasonic Electronics
in 2007 and 2011, respectively. He also received the Japanese Journal of Applied Physics Editorial Contribution Award from the Japan Society of Applied
Physics (JSAP) in 2007. He is a Member of the IEEE, the ASJ, the JSAP, theIEICE, and the Institute of Electrical Engineers of Japan.