Optical Sensing Systems Based on Depressed Cladding Erbium Doped Fiber

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JOURNAL OF LIGHTWAVE TECHNOLOGY, VOL. 30, NO. 8, APRIL 15, 2012

Optical Sensing Systems Based on Depressed Cladding Erbium Doped Fiber Joao Batista Rosolem, Mauro Biscaro Elias, Livia Alves Ribeiro, and Carlos Kenichi Suzuki (Invited Paper)

Abstract—This work describes new types of optical sensing systems based on Depressed Cladding Erbium Doped Fiber (DC-EDF). Due to the amplification characteristics developed for S-Band uses, this sensing system has high sensitivity, high dynamic range and wide bandwidth. It can be used to monitor static parameters such as force, pressure, displacement and dynamic parameters used in acoustics and vibrations. Two types of sensing systems with different approaches have been studied: the amplifier and the laser sensor. We describe the performance of these sensing systems in S band (1490 and 1510 nm) in static and dynamic conditions. We also appointed for some sensing applications for many areas of interest, such as, electric energy and civil engineering. Index Terms—Depressed cladding fiber, erbium doped fiber, erbium ring laser, fiber bending sensor, fiber loop sensor, S band.

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I. INTRODUCTION

IBER bending or fiber loop sensors have been studied since the eighties involving many different fibers as multimode, single mode and especial curvature fibers [1], [2]. When fiber optic bending sensor is used many physical parameters can be measured, e.g., forces, pressure, vibration, frequencies and other acoustic parameters. Many applications of bending fiber sensors have been reported in [1]. Depressed Cladding Erbium Doped Fiber (DC-EDF) is an interesting special fiber that uses the bending mechanism to obtain optical amplification in S-Band (1480–1525 nm). DC-EDF was developed a few years ago to be used in Dense Wavelength Division Multiplexing (DWDM) channel expansion [3], [4]. It has been pointed out that the behavior of DC-EDF is very sensitive to the bending radius, which is used to suppress the C-Band amplified spontaneous emission (ASE) generated by erbium doped fiber, thus enabling S-Band optical amplification. A method to tune the gain of a double-pass amplifier based on DC-EDF fiber using an adjustable elliptical coil has been reported [4]. DC-EDF is applied particularly in optical amplifiers, however its application as a ring laser cavity has also became a high Manuscript received June 28, 2011; revised October 12, 2011; accepted October 25, 2011. Date of publication October 28, 2011; date of current version March 16, 2012. J. B. Rosolem and L. A. Ribeiro are with the CPqD—Research and Development Center in Telecommunications, Campinas, SP 13086-902, Brazil (e-mail: [email protected]; [email protected]). M. B. Elias and C. K. Suzuki are with State University of Campinas, Campinas, SP 13083-970, Brazil (e-mail: [email protected]; [email protected]). 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.2011.2174139

interesting subject. Some research works [5], [6] have studied these lasers and their mechanism of tunability, as well as, the description of ring laser which the mechanism of tunability is based on standard erbium doped fiber application [7], [8]. By considering the DC-EDF amplification and lasing bend dependence characteristics, this paper analyzes the application of this fiber as a sensor. The bending characteristics of the sensing systems based on DC-EDF promise better sensitivity, dynamic range and bandwidth when they are compared with standard fiber optic bending sensors or other types of fiber optic sensors. They can be used by means of direct detection to monitoring static parameters such as force, pressure, displacement and dynamic parameters used in acoustics and vibrations. We describe the sensing systems using the DC-EDF sensor in two configurations: amplifier sensor and laser sensor. The sensing systems were characterized in S band for both static and dynamic condition. Our purpose is to explore the bending/ amplification or bending/lasing mechanism of DC-EDF in order to obtain a sensor highly sensitive which can be used in many areas of interest, such as, electric energy and civil engineering. II. SENSOR AND SENSING SYSTEMS BASED ON DC-EDF The principle of operation of the proposed fiber sensing systems is based on the DC-EDF which is the sensor itself. The DC-EDF can also be referred to as dual-clad or “W-profile” erbium doped fiber. It has been demonstrated that the ASE of erbium-doped fibers can be suppressed in the C-Band, to take advantage of the S-Band amplification, due to the fundamental mode cutoff of DC-EDF [3]. The design of a DC-EDF has the cutoff wavelength at about 1525 nm and distributed loss in the S-Band much lower than the gain. Distributed fiber loss or distributed fiber gain at S-Band depends on fiber bending to suppress the C-Band ASE in a certain bending radius which is generally smaller than 50 mm. The basic configurations of the DC-EDF sensing systems analyzed in this work are depicted in Fig. 1(a) and (b). In Fig. 1(a) the DC-EDF sensor is used as a double pass amplifier (amplifier sensor). The double pass setup improves the gain performance when compared to a single pass amplification setup [4]. A circulator was used at the sensing system input to couple light in and out of the doped fiber while the erbium-doped fiber is pumped by a co-propagating pump scheme. Pumping is carried out by a 980 nm laser. A Faraday rotator mirror (FRM) was placed at the opposite end of the erbium-doped fiber to assure around 95% reflection back into the amplification circuit. We utilized coarse wavelength division multiplexing (CWDM) S-Band distributed-feedback lasers (DFB) operating

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ROSOLEM et al.: OPTICAL SENSING SYSTEMS BASED ON DEPRESSED CLADDING ERBIUM DOPED FIBER

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Fig. 2. ASE power in the amplifier sensor output, with different R. The Ppump was 18 dBm at 980 nm.

Fig. 1. DC-EDF as sensor used in (a) amplifier sensor (double pass amplifier) and (b) laser sensor (ring laser).

in 1490 and 1510 nm to excite the DC-EDF. Due to CWDM grid standardization [9] there are three wavelengths in the CWDM grid for S band, 1470 nm, 1490 nm and 1510 nm, but only for the last two ones there are significant gain provided by DC-EDF. Fabry–Perot lasers (FP) can also be used as light source although they are not easily available for S band operation. The main mechanism of sensing for the amplifier sensor is the mode suppression by bending the fiber. Since in standard EDF the amplification in the S band is not too efficient in DC-EDF the process the amplification is improved through the suppression of ASE in the C-band region (1525 to 1560 nm). This is carried out by exploiting the fundamental mode cutoff wavelength of the DC-EDF that is dependent of the fiber parameters, such as, depressed index profile, core and cladding radius and the bending fiber radius (R) [10]. For wavelengths above the substantial optical power is transferred from the mode in the the core to the cladding mode. For wavelengths below the progressive reduction of bending fiber radius not only suppress the C band ASE power but it allows tuning the gain in S band according the wavelength of the signal to be amplified. The progressive reduction of bending radius moves the peak gain at S band towards short wavelengths. Fig. 1(b) shows the DC-EDF sensor used as a ring laser (laser sensor). An optical splitter (90/10%) was used at the sensing system output to obtain a sample laser light (10% port) and to connect the counter-propagating ASE power generated by the near end DC-EDF (90% port) in to the far end of DC-EDF. The laser stability and tuning were achieved by using an isolator and a tunable optical filter (FO) in the feedback loop, respectively. The DC-EDF was pumped by a co-propagating pump scheme by using a 980 nm laser. The amplifier sensor configuration is simpler and cheaper than the laser sensor configuration, but the latter is more flexible particularly if a tunable filter is used to choose the operating wavelength inside the S band. In this case it enables the implementation of a WDM sensor network. The mechanism of sensing of the laser sensor proposed in this work is different from the amplifier sensor. The laser

sensor also uses fiber bending to C band ASE suppression but the tunnability is achieved by tuning the optical filter. Laser sensor also needs more S band ASE power to start the process of lasing, it means, the DC-EDF bending radius could not be too small because like in sensor amplifier small bending radius reduces the total ASE power. By the other hand, the optical signal-to-noise ratio (OSNR) of laser sensor should be better than the amplifier sensor, making it more advantageous for sensing signals of low intensity. In some sensing applications, such as acoustic detection, for example, fiber coil Radius R will not suffer large increasing or decreasing. It will remain practically constant. III. SENSING SYSTEMS DESIGN The optimization of the DC-EDF sensing/bending radius mechanism is one critical issue to be considered in order to obtain the best sensor performance in both sensing system. Some numerical and theoretical models have been proposed as a tool for design S band depressed cladding amplifiers [10]–[13], but in general these models are too complex for practical uses and also the main DC-EDF parameters, such as, depressed index profile and depressed cladding radius are not easily to obtain. In this work we designed the sensors based in the DC-EDF experimental characterization data. We are developing a new model to optimize the proposed sensing systems, where we include the main physical sensing parameters, such as, force, pressure and oscillation frequencies. The DC-EDF used in this work employs an Er-La-Al-doped core with 7.6 dB/m pump absorption in 980 nm. The C-Band bending loss exceeds 10 dB/m when a 30 mm coil radius is used. Fig. 2 shows the ASE power in the amplifier sensor output, with different bending radius. In this experiment no input power was injected in the amplifier sensor. The pump power was 18 dBm at 980 nm. It can be observed that the progressive reduction of bending radius diminish the total power, also moves the peak gain at S band towards short wavelengths reducing also the peak power. If the goal is to sense compression force, for example, the R should be determined by the optimized bend radius indicated as the dashed line in Fig. 2, at one specific wavelength. The optimized bend radius is radius for each ASE peak power (the

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Fig. 5. Some examples of spectral lines of the laser sensor.

Fig. 3. Amplified sensor output with dBm, sion forces. Input power dBm at 980 nm, DC-EDF

mm, used to sensing compresnm, m.

Fig. 6. Set up to sensing systems characterization.

Fig. 4. Gain and OSNR versus input power for the sensor amplifier for 1490 and 1510 nm.

ASE peak power coincides with the gain peak of the sensor), but if the sensing parameter is an oscillatory process, such as vibrations or acoustics the best choice for R is in the upward or downward section of the bending curve. Fig. 3 shows one example of amplified sensor output with mm, used for sensing compression forces. The remm was ducing in the radius from the initial value done by compressing the loop fiber. Fig. 4 shows the gain and the OSNR versus input power for the sensor amplifier in two S band wavelengths 1490 and 1510 nm for mm. Measurement of low power signals usually have a poor OSNR, in contrast our sensor shows itself as an important tool for such kind of measurement since as we can observe for high input power the OSNR is high even with low gain signal. The laser sensor can be designed observing the same rules. Since the feedback loop shown in Fig. 1(b) provides enough ASE power, the ring laser will oscillate in the tuned S band frequencies.

Fig. 5 shows some tuned ring laser spectral lines of the laser sensor used in this work. In this case, the DC-EDF length was 12 m long and coiled in a loop radius mm. This change was necessary to obtain enough ASE so that oscillation could be promoted. The spectral operation is limited in a 1495 nm to 1517 nm work range, the former occur due to optical filter tuning range and the latter to the DC-EDF wavelength fundamental mode cutting. The OSNR for the laser sensor is around 38 dB that is slightly higher than the amplifier sensor. IV. SENSING SYSTEM EVALUATION IN STATIC CONDITION The amplifier sensor system was characterized in S-band in static condition, i.e., when the sensed parameter changes in a very low frequency, such as, pressure in dams or forces in civil structures. In the static condition we measured the output signal of amplifier sensor by changing the DC-EDF bending radius (R) using a calibrated compression setup. In order to characterize this sensing systems its output (out) was connected to an optical receiver Rx (photo-detector (PD) plus trans-impedance amplifier (TIA)), followed by an electric amplifier and an oscilloscope (Fig. 6). The S-band DFB laser of amplifier sensor was modulated at 1.9 kHz, with 500 ns pulse duration. The laser sensor was not characterized in the static condition since it could not be modulated like the amplifier sensor. Fig. 7 shows the useful attenuation behavior of amplified sensor for two different DC-EDF radius loops compared with a

ROSOLEM et al.: OPTICAL SENSING SYSTEMS BASED ON DEPRESSED CLADDING ERBIUM DOPED FIBER

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Fig. 7. The useful attenuation behavior of amplified sensor for DC-EDFs with initial bended radius (R) of 24.6 mm and 34.1 mm compared with a simple double pass bend sensor using single mode fiber.

standard single-mode fiber optic loop sensor. The first DC-EDF sensor depicted was 2 m long, with initial bended radius mm, the second one was 10 m long with mm. The signal input power at 1490 nm was dBm, and was 18 dBm at 980 nm. The useful attenuation is defined as the ratio of the amplified pulsed signal in each bending radius by the amplified pulsed signal in the R. The major attenuation point in each curve corresponds to the minimum visible signal in the oscilloscope. For comparison purposes we inserted in the same plot the attenuation of one simple double pass bend sensor using single mode fiber (STM-28) at the wavelength of 1625 nm. This sensor has the initial bended radius of 13.7 mm and 13 fiber loops. We can observe in Fig. 7 that for both DC-EDF initial radius the dynamic range is major than the single-mode fiber. Particularly for the DC-EDF sensor with mm the dynamic range is 6 dB higher than single-mode fiber sensor. Fig. 7 shows a very good result of useful attenuation (16.5 dB in the 34.1–25.7 mm radius variation range) when it is compared with other fiber optic bending sensors [1], [2]. In [1], for example, Sumitomo graded fiber presented useful attenuation of 7 dB for 50 mm radius variation. In a more recently work [2] a useful attenuation of 10 dB was obtained in a standard single mode fiber (SMF-28) in the range from 0.5 to 7.5 mm radius variation from an original bending radius of 8 mm. V. SENSING SYSTEMS EVALUATION IN DYNAMIC CONDITION The sensing systems were also characterized in dynamic condition, i.e., when the sensed parameter changes in a very high frequency, such as, vibration due to the earthquakes or ultrasound vibrations due to the partial discharges in hydro-generators and in high voltage transformers, becoming as an option to the former optical interferometric sensors [14]. A. Amplifier Sensor In the dynamic condition the DC-EDF fiber was mechanically excited by one acoustic transducer whose electrical signal was supplied by an audio signal generator and amplified by an electrical amplifier (Fig. 6). A calibrated Hall sensor was coupled to the acoustic transducer in order to measure the mechanical

Fig. 8. Peak-to-peak voltage in the amplifier sensor output for vibration freat signal wavelengths of (a) quency of 100 Hz versus the radius variation 1490 nm and (b) 1510 nm.

displacement in the DC-EDF radius caused by acoustic transducer. The DC-EDF 10 m long coiled in loop radius mm was oriented in a vertical position (see the inset in Fig. 6) and it was fixed in two points. First the DC-EDF was mechanically excited by the acoustic transducer set at 100 Hz, in different radius variations ranging from 30 to 300 m. Figs. 8(a) and (b) show the linear behavior of the peak-to-peak voltage measured by the optical receiver Rx versus the radius variation at 1490 nm (Fig. 8(a)) and at 1510 nm (Fig. 8(b)) for three input power levels of dBm, dBm and dBm. The S band DFB lasers operated in CW mode (Continuous Wave) in this experiment. Next, the vibration frequency was changed from 10 Hz to 15 kHz and was maintained in 13 m. Fig. 9 shows the spectral performance of DC-EDF amplifier sensor at 1490 and 1510 nm. The behavior of the amplifier sensor is very similar in these two wavelengths. It is possible to observe the formation of resonance peaks in the sensor signal. The spectral behavior is certainly no flat but the sensitivity is very good from low to high frequencies. Fig. 9 also shows that the maximum detectable vibration frequency for the amplifier sensor was around 14 kHz. The spectral response of the fiber bending sensor can be understood using a simplified model of string resonance. The sensor resonance has dependence with some fiber loop parameters such as applied strain, length, radius, points of fixing (acoustic nodes) and fiber material constants [15], [16]. When the fiber loop is tensioned by the acoustic transducer the transverse waves propagate to the fixing end point where they

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Fig. 9. Spectral performance of DC-EDF amplifier sensor from 10 Hz to mm and m. 10 kHz for

JOURNAL OF LIGHTWAVE TECHNOLOGY, VOL. 30, NO. 8, APRIL 15, 2012

Fig. 11. Spectral performance of DC-EDF laser sensor from 5 Hz to 60 kHz mm and m. for

TABLE I COMPARISON BETWEEN THE TWO SENSING TECHNIQUES

Fig. 10. Peak-to-peak voltage in the laser sensor output for vibration frequency at signal wavelengths of 1495 nm, of 100 Hz versus the radius variation 1500 1505 nm and 1510 nm.

are reflected undergoing constructive interference and leading to the resonance frequencies. B. Laser Sensor Similar to the amplifier sensor, the laser sensor was mechanically excited by the acoustic transducer according the setup shown in Fig. 5. First, the DC-EDF fiber was mechanically excited by the acoustic transducer in a frequency of 100 Hz in different ranging from 17 to 727 m. Fig. 10 shows the linear behavior of the peak-to-peak voltage measured in the optical receiver Rx versus the radius variation for four selected wavelengths (1495 nm, 1500 nm, 1505 nm and 1510 nm). Next, the vibration frequency was changed from 5 Hz to 60 kHz and was maintained in 4 m. Fig. 11 shows the spectral performance of DC-EDF laser sensor system at 1495 and 1510 nm. The behavior of the laser sensor is similar for these two wavelengths and also is similar of the behavior of the amplifier sensor. Because of the limitations of the acoustic transducer, the measurements could not extend above 60 kHz. The laser sensor has shown better performance when it is compared with the amplifier sensor in terms of bandwidth, as we can observe in Figs. 9 and 11, but the amplifier sensor has shown better sensitivity as we can observe in Figs. 8(a), (b) and 10, where sensitivity is defined by the rate: peak-to-peak voltage

by maximum . The Table I summarizes the comparison between the two techniques. The better performance of amplifier sensor when compared to the laser sensor, in terms of minimum detectable radius variation and sensitivity can be explained due to the output power provided by amplification is higher than the power provided by lasing process. On the other hand, the laser sensor showed better performance in terms of bandwidth, which can be explained due to its better OSNR high frequencies compared to amplifier sensor. As we can observe in Fig. 11 the laser sensor can detect vibrations at ultrasonic frequencies range ( kHz) what enable its use in many interesting applications, such as in partial discharge detection in power transformers and hydro-generators. The laser sensor ability to detect low frequencies ( Hz) is a promising tool that might be used to detect vibrations in large structures such as bridges and dams. Finally, for the best of our knowledge, the maximum detectable vibration frequency presented in Table I is the highest level measured till this moment [17]–[19], since literature presented the maximum detectable vibration frequency was 4.7 kHz in [12], it was 0.4 kHz in [18] and it was 1.9 kHz in [19]. VI. CONCLUSION This work described new types of optical sensing systems based on Depressed Cladding Erbium Doped Fiber (DC-EDF). Due to the amplification characteristics developed for S-Band applications this sensing system has high sensitivity, high dynamic range and wide bandwidth. They can be used to monitor static parameters such as force, pressure, displacement and dynamic parameters such as in acoustics and vibrations. We also

ROSOLEM et al.: OPTICAL SENSING SYSTEMS BASED ON DEPRESSED CLADDING ERBIUM DOPED FIBER

pointed out some sensing applications for many areas of interest, such as electric energy and civil engineering. Two types of sensing systems have been studied: the amplifier sensor and the laser sensor. We described the sensing systems characterization in S band (1490 to 1510 nm) in two different conditions: static and dynamic. They showed good performances in frequencies from 5 Hz to 60 kHz, particularly the DC-EDF laser sensor. REFERENCES [1] F. Lagakos, J. H. Cole, and J. A. Bucaro, “Microbend fiber-optic sensor,” Appl. Opt., vol. 26, no. 11, pp. 2171–2180, Jun. 1987. [2] N. Q. Nguyen and N. Gupta, “Power modulation based fiber-optic loopsensor having a dual measurement range,” J. Appl. Phys., vol. 106, no. 3, 2009. [3] M. A. Arbore, Y. Zhou, G. L. Keaton, and T. Kane, J. Nagel, S. Namiki, and L. Spiekman, Eds., “36 dB gain in S-band EDFA with distributed ASE suppression,” Opt. Ampl. Their Appl., vol. 77, 2002, Paper PD4.. [4] J. B. Rosolem, A. A. Juriollo, R. Arradi, A. D. Coral, J. C. R. F. Oliveira, and M. A. Romero, “All silica S-Band double-pass erbium-doped fiber amplifier,” IEEE Photon. Technol. Lett., vol. 17, no. 7, pp. 1399–1401, Jul. 2005. [5] C. H. Ye, C. C. Lee, and S. Chi, “A tunable S-band erbium-doped fiber ring laser,” IEEE Photon. Technol. Lett., vol. 15, no. 8, pp. 1053–1054, Aug. 2003. [6] M. Foroni, F. Poli, A. Cucinotta, S. Selleri, and P. Vavassori, “S band erbium-doped fiber ring laser tunable through the active fiber bending losses,” in Proc. OFC/NOEFC, 2007, Paper JThA9. [7] M. Qiu, M. A. Rebolledo, J. M. Alvarez, and M. V. Andres, “Stress modulation and wavelength tuning of an erbium-doped optical fiber laser,” Opt. Lett., vol. 18, pp. 508–510, 1993. [8] N. K. Chen, S. Chi, and S. M. Tseng, “An efficient local fundamentalmode cutoff for thermo-optic tunable Er3+-doped fiber ring laser,” Opt. Exp., vol. 13, pp. 7250–7255, 2005. [9] Spectral Grids for WDM Applications: CWDM Frequency Grid, ITU-T G.694.2, 2002. [10] M. A. Arbore, G. L. Keaton, Y. Zhou, T. Kane, and J. D. Kmetec, “Communication System and Split Band Amplifying Apparatus Using a Depressed Profile Fiber Amplifier,” U.S. Patent WO03/076979, Sep. 18, 2003. [11] K. Thyagarajan and C. Kakkar, “S-band single-stage EDFA with 25-dB gain using distributed ASE suppression,” IEEE Photon. Technol. Lett., vol. 16, pp. 448–450, 2004. [12] L. Vincetti, M. Foroni, F. Poli, M. Maini, A. Cucinotta, S. Selleri, and M. Zoboli, “Numerical modeling of S-band EDFA based on distributed fiber loss,” J. Lightw. Technol., vol. 26, no. 14, pp. 2168–2174, Jul. 2008. [13] C. E. Chan, S. D. Emami, P. Hajireza, H. Y. Beh, S. A. Daud, S. S. Pathmanathan, S. W. Harun, H. Ahmad, and H. A. A. Rashid, “Optimization of fiber length and bending diameter in depressed cladding erbium-doped fiber amplifier,” in Proc. 2009 IEEE 9th Malaysia Int. Conf. Commun., Kuala Lumpur, Malaysia, 2009. [14] C. Macià-Sanahuja, H. Lamela, and J. A. García-Souto, “Fiber optic interferometric sensor for acoustic detection of partial discharges,” J. Opt. Technol., vol. 74, pp. 122–126, 2007. [15] M. N. Zervas and I. P. Giles, “Resonant-loop optical fibre phase modulator,” in Proc. Int. Conf. Opt. Fiber Sens. OSA Techn. Digest Series, 1988, vol. 2, pp. 150–153. [16] S. Knudsen, G. B. Havsgard, O. Christensen, G. Wang, A. B. Tveten, and A. Dandridge, “Bandwidth limitations due to mechanical resonances of fiber-optic air-backed mandrel hydrophones,” in Proc. Int. Conf. Opt. Fiber Sens. OSA Techn. Digest Series, 1997, vol. 16, pp. 544–547. [17] F. Honggang, W. Fan, and Q. Sheng, “Experimental study on vibration frequency response of micro-bend optic-ber sensor,” Chin. Opt. Lett., vol. 7, no. 7, pp. 556–559, 2009.

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[18] N. D. Linze, M. Wuilpart, C. Caucheteur, K. Chah, O. Verlinden, and P. Mégret, “Using a bent optical fiber and polarization-sensitive detection for vibrations measurements,” in Proc. OSA Tech. Dig., 2010, Paper SWD3. [19] Q. Wu, Y. Semenova, P. Wang, and G. Farrell, “The use of a bent singlemode-multimode-singlemode (SMS) fiber structure for vibration sensing,” in Proc. SPIE 21st Int. Conf. Opt. Fiber Sens., 2011, vol. 7753, Paper 7753-174. Joao Batista Rosolem was born in Fartura, SP, Brazil, in 1963. He received the B.S., M.Sc., and Ph.D. degrees in electric engineering from the University of Sao Paulo, Sao Carlos, Brazil, in 1986, 1990, and 2005, respectively. Since 1990, he has been a researcher of CPqD Telecommunication Research and Development Center, Campinas, Brazil. He has been involved in the design and characterization of optical system and research in optical amplifiers and optical sensors. He has also been engaged in the development of trunk and access wavelength division multiplexing (WDM) transmission systems. He is the holder of 3 U.S. patents and more than 7 additional patents are pending in the Brazil. Dr. Rosolem is member of Optical Society of America (OSA) and is author of over 100 journal and conference papers.

Mauro Biscaro Elias was born in Penapolis, Brazil, in 1955. He received the graduation degree in physical from State University of Campinas—Unicamp, Campinas, Brazil, in 1978. In 1980 he received the Master of Science degree in physical from UNICAMP and is completing working toward the Ph.D. degree in mechanical engineering (UNICAMP). From 1980 to 1988, he was General Manager of XTAL Optical Fibers, a Brazilian fiber manufacturer. From 1988 to 1989 he was Optical Fiber Cable Division Manager at Alcatel Cables Brazil. From 1990 to 1995, he was Manager of Optoelectronics Division of Avibras, a Brazilian defense system manufacturer. From 1996–2003 he was Director of Lightwave, a company whose main assignment was to plan optical fiber plants, and supported Tecsat Optical Fiber in its optical fiber operation. From 2004–2008 he was rep of j-fiber in Brazil. In 2008 he joined JáOD (Já! Optical Devices), a company of CPqD.

Livia Alves Ribeiro was born in Santo André, São Paulo, Brazil, on 1980. She received the B.S. and M.Sc. degrees in physics from the University of São Paulo, São Paulo, Brazil in 2002 and 2006, respectively. Since 2007 she is enrolled at National Institute for Spatial Research (INPE), São José dos Campos, Brazil working toward the Ph.D. degree on Distributed Optical Fiber Sensors based on Raman scattering. She has been a partner of Institute for Advance Studies, an Air Force Brazilian institute since 2007. In 2011, she joined as a research of CPqD Telecommunication Research and Development Center, Campinas, Brazil working on optical fiber sensors. Ms. Ribeiro is a member of Optical Society of America (OSA).

Carlos Kenichi Suzuki was born in São Paulo, Brazil, on June 19, 1945. He received the B.S. and M.Sc. degrees in applied physics from São Paulo University, and the State University of Campinas, Campinas, Brazil, in 1969 and 1974, respectively, and the Dr. Eng. degree in applied physics engineering from the University of Tokyo, Japan, in 1981. In 1982, he joined the Optical Fiber Project of Telebras-Unicamp, where he was engaged in the development of optical fiber preform. From 1984 to 1990, he coordinated the international cooperation projects of JICA-Unicamp and METI/ ITIT-Unicamp, developing highly perfect synthetic quartz and high-purity silica glass. From 1990 to 1993, he was a Research Fellow at the Spring-8 Laboratory, Harima, Japan. In 1994, he was a Professor of Materials Engineering in the area of new VAD technology at The State University of Campinas. He is author of over 160 journal and conference papers and holder of 12 patents in Brazil and 1 PCT patent. Dr. Suzuki is a member of the IEEE Photonic Society.

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