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Bismuth core fibers
Materials Letters 186 (2017) 308–310
Contents lists available at ScienceDirect
Materials Letters journal homepage: www.elsevier.com/locate/matlet
crossmark
Bismuth core fibers ⁎
Guowu Tang, Min Sun, Wangwang Liu, Qi Qian , Guoquan Qian, Kaimin Huang, Dongdan Chen, ⁎ Zhongmin Yang
State Key Laboratory of Luminescent Materials and Devices, Special Glass Fiber and Device Engineering Technology Research and Development Center of Guangdong Province, Guangdong Provincial Key Laboratory of Fiber Laser Materials and Applied Techniques, and Institute of Optical Communication Materials, South China University of Technology, Guangzhou 510640, China
A R T I C L E I N F O
A BS T RAC T
Keywords: Fiber optics Optical fiber Magnetic materials Fiber optic sensors
Elemental bismuth (Bi) exhibits a high magnetoresistance as a typical example of semimetal, which has significant application in information technologies. Silicate glass-clad Bi core fibers were fabricated by a molten core method and maintained core diameter of 100–150 µm and overall diameter of 300–450 µm. X-ray diffraction (XRD) and micro-Raman spectra showed the core to be highly crystalline with no observed secondary phases. Electro-probe micro-analyzer (EPMA) measurements confirmed a very well-defined core-clad interface. Demonstration of fibers with high magnetoresistance core materials and the potential integration with current state of the art technologies represents the first step in providing the building blocks for all-fiber sensors.
1. Introduction Fiber optics research has attracted much attention during recent years by the integration of materials that are traditionally not used in fiber optics [1,2]. Semiconductors, metals, new dielectric materials, and metamaterials have been integrated into fibers by high-pressure chemical vapor deposition (HPCVD), pressure-assisted melt filling (PAMF), or molten core approach, which provide a novel class of one-dimensional photonic devices that are flexible and even potentially wearable [3–8]. The HPCVD method can be easily adapted to deposit various materials into a range of pore size, which can be used to fabricate semiconductor and metallic wires microstructured optical fibers [9]. However, the lengths of fiber are limited due to the slow deposition rate [10]. Compared with the HPCVD technique, the PAMF method is useful for applications where long lengths of low loss fiber are required. However, the high temperature process does result in significant diffusion of oxygen from the cladding glass into the core material during the drawing process, which may ultimately place a limit on the minimum obtained core sizes [11]. The molten core method has been widely employed to the fabrication of several types of multimaterial fibers [1,11,12]. The cladding glass acts as a crucible that both contains the core material as it melts and serves as the cladding for the resultant optical fiber upon drawing [12]. In general, a core phase, which can be particulate or bulk, crystalline, polycrystalline or even amorphous, is sleeved inside a glass cladding and molten at the draw temperature of ⁎
the cladding glass. It is versatile, practical, and yields long lengths of multimaterial fibers. Already, multiple materials with disparate photonic, optoelectronic, acoustic, piezoelectric, and thermomechanical, superconducting properties have been monolithically integrated into the same fiber, which is paving the way to a new generation of multimaterial fiber endowed with unique functionalities delivered at optical fiber length scales and costs [8–13]. It is well-known that the semimetals are new platforms to realize a huge magnetoresistance, an effect that has been pursued intensively in emerging materials in recent years, because of their significant applications in sensing and information technologies [14]. Elemental Bi exhibits a high magnetoresistance as a typical example of semimetals [15]. Fiber optic sensing technologies stand to benefit from the pursuit of all-fiber optoelectronics. As for example, magnetic fiber optic sensors typically require the use of a magnetostrictive material such as Metglas or Terfenol-D that is bonded to an optical fiber or incorporated into a laser ablated micro-slot in the fiber [16]. However, core materials with high magnetoresistance have not been integrated into fibers for all-fiber sensors. In this work, a high magnetoresistance material of Bi was successfully integrated into fibers by a molten core method. Demonstration of fibers with high magnetoresistance core materials and the potential integration with current state of the art technologies represents the first step in providing the building blocks for all-fiber sensors.
Corresponding authors. E-mail addresses: [email protected] (Q. Qian), [email protected] (Z. Yang).
http://dx.doi.org/10.1016/j.matlet.2016.10.050 Received 10 May 2016; Received in revised form 29 September 2016; Accepted 11 October 2016 Available online 12 October 2016 0167-577X/ © 2016 Elsevier B.V. All rights reserved.
Materials Letters 186 (2017) 308–310
G. Tang et al.
2. Experiments 2.1. Sample preparation Bi powder of 99.99% purity (Aladdin Industrial Corporation, Shanghai, China) was filled in a silica glass tube with diameter of 3 mm. Then the glass tube was heated at 700 °C for 30 min under vacuum condition, after which they were cooled to room temperature. Then, a 5-cm-long Bi rod with diameter of 3 mm was obtained by removing the silica glass tube. The Bi rod was filled in a 5-cm-long commercial Pyrex 3.3 borosilicate glass tube with outer diameter of 8 mm and inner diameter of 3 mm. The continuous Bi core fibers were drawn at about 860 °C by using an optical fiber draw tower under an argon atmosphere. 2.2. Characterization Fibers were cleaved and polished and their cross sections were characterized with an electro-probe micro-analyzer (EPMA-1600, Shimadzu, Kyoto, Japan). The element distribution of the fiber cross section was performed using the EPMA operated at 20 kV under vacuum atmosphere. The crystalline phase in fiber core was identified by X-ray powder diffractometer (X'Pert PROX, Cu Kα). Micro-Raman spectra were recorded by a Raman spectrometer (Renishaw in Via, London, UK) excited by a 532 nm laser.
Fig. 2. XRD patterns of the Bi powder and Bi core in fiber.
3. Results Fig. 1(a) shows the electron micrograph image of a fiber end face with a 125-μm-diameter core and 275-μm-diameter cladding. There exist no vacuum bubbles and microcracks and the boundary between core and cladding is clear. In order to determine element distribution of the fiber core and clad after fiber drawing, EPMA measurements were performed on the cross section of the fiber. Figs. 1(b) and (d) show the elements of Si and O distribute in the cladding region, while the element Bi distributes in the core region (Fig. 1(c)). The distribution boundary of each element forms a circle and exhibits similar size as that of the fiber core as shown in Fig. 1(a). These results indicate that the core-clad structure of fiber is preserved completely. The XRD patterns of the Bi powder and Bi core in fiber are shown in Fig. 2. It can be observed that all the reflection peaks in the pattern of the Bi powder can be well-indexed to the hexagonal bismuth phase (JCPDS No. 05-0519). The XRD pattern of the fiber core is also provided in Fig. 2. Clearly observed are peaks of fiber core well-indexed to the crystallographic reflections of Bi powder suggesting that the phase purity of the core that solidifies from the melt as the fiber cools. The results indicate that the high degree of crystallinity of Bi core was obtained after the fiber drawing. Fig. 3 presents the Micro-Raman spectra for the Bi powder and Bi core in the fiber. As can be seen, the Raman bands peak at 69 and
Fig. 3. Micro-Raman spectra from the Bi powder and Bi core in fiber.
93 cm−1, which can be assigned to the Eg and to the A1g first-order Raman modes of semimetallic bismuth [17]. It is worth noting that the fiber core shows the very similar Raman spectra to those of the Bi powder, indicating high degree of crystallinity and phase purity in Bi core. The EPMA, XRD, and micro-Raman spectra showed that little oxygen diffused into the core region due to the fibers drawn at relative lower temperature. 4. Discussion The challenge to integrate functional materials into multimaterial
Fig. 1. (a) Electron image of the Bi core fiber in cross section, (b)–(d) the EPMA images of the fiber in local cross section.
309
Materials Letters 186 (2017) 308–310
G. Tang et al.
fibers are the melting point and volatilization temperature of core material, heating rate, draw temperature, draw speed, core to clad ratio, and the coefficients of thermal expansion (CTE) of the materials and their chemical compatibilities [10,16,18]. The melting point and boiling point of Bi are 271.5 and 1564 °C, respectively. And the multimaterial fibers were drawn at 860 °C, which is higher than the melting point of Bi but lower than its boiling point. Therefore, the glass cladding can be directly drawn into fibers where the core precursor phase is molten, which goes “along for the ride” and ultimately solidified as the fibers cool [9]. The magnitude of the residual stresses in the as-drawn fibers is due to the unmatched CTE between glass cladding and core material. And the large residual stresses in the fibers will cause significant cracking and fiber breakage. The CTE of the Bi and silicate glass cladding are 1.1×10−4 and 3.3×10−6 K−1, respectively. It was found that smaller core to glass cladding ratios tended to reduce the tendency of glass cracking [16]. What is more, the raise of heating temperature was kept slow and gradation.
Distinguished Young Scientists (61325024), the High-level Personnel Special Support Program of Guangdong Province (2014TX01C087), Fundamental Research Funds for the Central Universities (2015ZP019), the Science and Technology Project of Guangdong (2015B090926010), China State 863 Hi-tech Program (2014AA041902) and NSFC (61535014 and 51302086). References [1] M.A. Schmidt, A. Argyros, F. Sorin, Adv. Opt. Mater. 4 (2016) 13. [2] G. Tao, A.F. Abouraddy, A.M. Stolyarov, Y. Fink, Multimaterial fibers. In: Lab-onFiber Technology, Springer International Publishing, 2015. pp. 1–26. [3] P.J.A. Sazio, A. Amezcua-Correa, C.E. Finlayson, J.R. Hayes, T.J. Scheidemantel, N.F. Baril, B.R. Jackson, D.J. Won, F. Zhang, E.R. Margine, V. Gopalan, V.H. Crespi, J.V. Badding, Science 311 (2006) 1583. [4] J. Ballato, T. Hawkins, P. Foy, R. Stolen, B. Kokuoz, M. Ellison, C. McMillen, J. Reppert, A.M. Rao, M. Daw, S.R. Sharma, R. Shori, O. Stafsudd, R.R. Rice, D.R. Powers, Opt. Express 16 (2008) 18675. [5] P. Dragic, T. Hawkins, P. Foy, S. Morris, J. Ballato, Nat. Photonics 6 (2012) 629. [6] G. Tang, Q. Qian, X. Wen, X. Chen, W. Liu, M. Sun, Z. Yang, Opt. Express 23 (2015) 23624. [7] A. Tuniz, K.J. Kaltenecker, B.M. Fischer, M. Walther, S.C. Fleming, A. Argyros, B.T. Kuhlmey, Nat. Commun. 4 (2013) 2706. [8] H.W. Lee, M.A. Schmidt, R.F. Russell, N.Y. Joly, H.K. Tyagi, P. Uebel, P.S.J. Russell, Opt. Express 19 (2011) 12180. [9] G. Tang, Q. Qian, X. Wen, G. Zhou, X. Chen, M. Sun, D. Chen, Z. Yang, J. Alloy. Compd. 633 (2015) 1. [10] S. Morris, J. Ballato, Bull. Am. Ceram. Soc. 92 (2013) 24. [11] A.C. Peacock, J.R. Sparks, N. Healy, Laser Photonics Rev. 8 (2014) 53. [12] A.C. Peacock, U.J. Gibson, J. Ballato, Adv. Phys.: X 1 (2016) 1. [13] D. Homa, G. Pickrell, G. Kaur, Mater. Lett. 121 (2014) 101. [14] C. Shekhar, A.K. Nayak, Y. Sun, M. Schmidt, M. Nicklas, I. Leermakers, U. Zeitler, Y. Skourski, J. Wosnitza, Z. Liu, Y. Chen, W. Schnelle, H. Borrmann, Y. Grin, C. Felser, B. Yan, Nat. Phys. 11 (2015) 645. [15] F.Y. Yang, K. Liu, K. Hong, D.H. Reich, P.C. Searson, C.L. Chien, Science 284 (1999) 1335. [16] D. Homa, G. Kaur, G. Pickrell, B. Scott, C. Hill, Mater. Lett. 133 (2014) 135. [17] K. Trentelman, J. Raman Spectrosc. 40 (2009) 585. [18] A.F. Abouraddy, M. Bayindir, G. Benoit, S.D. Hart, K. Kuriki, N. Orf, O. Shapira, F. Sorin, B. Temelkuran, Y. Fink, Nat. Mater. 6 (2007) 336.
5. Conclusions In conclusion, a new kind of multimaterial fibers with Bi core and silicate glass cladding was fabricated by a molten core method. The Bi core was found to be highly high degree of crystallinity and phase purity. Fiber optic sensing technologies stand to benefit from the pursuit of all-fiber optoelectronics. This study constitutes a proof-ofconcept that magnetic fiber optic sensors require the use of a high magnetoresistance material of Bi can be incorporated into fibers by using conventional fiber fabrication techniques, which is significant to the field of multimaterial fibers. Acknowledgments This research was supported by China National Funds for
310
Contents lists available at ScienceDirect
Materials Letters journal homepage: www.elsevier.com/locate/matlet
crossmark
Bismuth core fibers ⁎
Guowu Tang, Min Sun, Wangwang Liu, Qi Qian , Guoquan Qian, Kaimin Huang, Dongdan Chen, ⁎ Zhongmin Yang
State Key Laboratory of Luminescent Materials and Devices, Special Glass Fiber and Device Engineering Technology Research and Development Center of Guangdong Province, Guangdong Provincial Key Laboratory of Fiber Laser Materials and Applied Techniques, and Institute of Optical Communication Materials, South China University of Technology, Guangzhou 510640, China
A R T I C L E I N F O
A BS T RAC T
Keywords: Fiber optics Optical fiber Magnetic materials Fiber optic sensors
Elemental bismuth (Bi) exhibits a high magnetoresistance as a typical example of semimetal, which has significant application in information technologies. Silicate glass-clad Bi core fibers were fabricated by a molten core method and maintained core diameter of 100–150 µm and overall diameter of 300–450 µm. X-ray diffraction (XRD) and micro-Raman spectra showed the core to be highly crystalline with no observed secondary phases. Electro-probe micro-analyzer (EPMA) measurements confirmed a very well-defined core-clad interface. Demonstration of fibers with high magnetoresistance core materials and the potential integration with current state of the art technologies represents the first step in providing the building blocks for all-fiber sensors.
1. Introduction Fiber optics research has attracted much attention during recent years by the integration of materials that are traditionally not used in fiber optics [1,2]. Semiconductors, metals, new dielectric materials, and metamaterials have been integrated into fibers by high-pressure chemical vapor deposition (HPCVD), pressure-assisted melt filling (PAMF), or molten core approach, which provide a novel class of one-dimensional photonic devices that are flexible and even potentially wearable [3–8]. The HPCVD method can be easily adapted to deposit various materials into a range of pore size, which can be used to fabricate semiconductor and metallic wires microstructured optical fibers [9]. However, the lengths of fiber are limited due to the slow deposition rate [10]. Compared with the HPCVD technique, the PAMF method is useful for applications where long lengths of low loss fiber are required. However, the high temperature process does result in significant diffusion of oxygen from the cladding glass into the core material during the drawing process, which may ultimately place a limit on the minimum obtained core sizes [11]. The molten core method has been widely employed to the fabrication of several types of multimaterial fibers [1,11,12]. The cladding glass acts as a crucible that both contains the core material as it melts and serves as the cladding for the resultant optical fiber upon drawing [12]. In general, a core phase, which can be particulate or bulk, crystalline, polycrystalline or even amorphous, is sleeved inside a glass cladding and molten at the draw temperature of ⁎
the cladding glass. It is versatile, practical, and yields long lengths of multimaterial fibers. Already, multiple materials with disparate photonic, optoelectronic, acoustic, piezoelectric, and thermomechanical, superconducting properties have been monolithically integrated into the same fiber, which is paving the way to a new generation of multimaterial fiber endowed with unique functionalities delivered at optical fiber length scales and costs [8–13]. It is well-known that the semimetals are new platforms to realize a huge magnetoresistance, an effect that has been pursued intensively in emerging materials in recent years, because of their significant applications in sensing and information technologies [14]. Elemental Bi exhibits a high magnetoresistance as a typical example of semimetals [15]. Fiber optic sensing technologies stand to benefit from the pursuit of all-fiber optoelectronics. As for example, magnetic fiber optic sensors typically require the use of a magnetostrictive material such as Metglas or Terfenol-D that is bonded to an optical fiber or incorporated into a laser ablated micro-slot in the fiber [16]. However, core materials with high magnetoresistance have not been integrated into fibers for all-fiber sensors. In this work, a high magnetoresistance material of Bi was successfully integrated into fibers by a molten core method. Demonstration of fibers with high magnetoresistance core materials and the potential integration with current state of the art technologies represents the first step in providing the building blocks for all-fiber sensors.
Corresponding authors. E-mail addresses: [email protected] (Q. Qian), [email protected] (Z. Yang).
http://dx.doi.org/10.1016/j.matlet.2016.10.050 Received 10 May 2016; Received in revised form 29 September 2016; Accepted 11 October 2016 Available online 12 October 2016 0167-577X/ © 2016 Elsevier B.V. All rights reserved.
Materials Letters 186 (2017) 308–310
G. Tang et al.
2. Experiments 2.1. Sample preparation Bi powder of 99.99% purity (Aladdin Industrial Corporation, Shanghai, China) was filled in a silica glass tube with diameter of 3 mm. Then the glass tube was heated at 700 °C for 30 min under vacuum condition, after which they were cooled to room temperature. Then, a 5-cm-long Bi rod with diameter of 3 mm was obtained by removing the silica glass tube. The Bi rod was filled in a 5-cm-long commercial Pyrex 3.3 borosilicate glass tube with outer diameter of 8 mm and inner diameter of 3 mm. The continuous Bi core fibers were drawn at about 860 °C by using an optical fiber draw tower under an argon atmosphere. 2.2. Characterization Fibers were cleaved and polished and their cross sections were characterized with an electro-probe micro-analyzer (EPMA-1600, Shimadzu, Kyoto, Japan). The element distribution of the fiber cross section was performed using the EPMA operated at 20 kV under vacuum atmosphere. The crystalline phase in fiber core was identified by X-ray powder diffractometer (X'Pert PROX, Cu Kα). Micro-Raman spectra were recorded by a Raman spectrometer (Renishaw in Via, London, UK) excited by a 532 nm laser.
Fig. 2. XRD patterns of the Bi powder and Bi core in fiber.
3. Results Fig. 1(a) shows the electron micrograph image of a fiber end face with a 125-μm-diameter core and 275-μm-diameter cladding. There exist no vacuum bubbles and microcracks and the boundary between core and cladding is clear. In order to determine element distribution of the fiber core and clad after fiber drawing, EPMA measurements were performed on the cross section of the fiber. Figs. 1(b) and (d) show the elements of Si and O distribute in the cladding region, while the element Bi distributes in the core region (Fig. 1(c)). The distribution boundary of each element forms a circle and exhibits similar size as that of the fiber core as shown in Fig. 1(a). These results indicate that the core-clad structure of fiber is preserved completely. The XRD patterns of the Bi powder and Bi core in fiber are shown in Fig. 2. It can be observed that all the reflection peaks in the pattern of the Bi powder can be well-indexed to the hexagonal bismuth phase (JCPDS No. 05-0519). The XRD pattern of the fiber core is also provided in Fig. 2. Clearly observed are peaks of fiber core well-indexed to the crystallographic reflections of Bi powder suggesting that the phase purity of the core that solidifies from the melt as the fiber cools. The results indicate that the high degree of crystallinity of Bi core was obtained after the fiber drawing. Fig. 3 presents the Micro-Raman spectra for the Bi powder and Bi core in the fiber. As can be seen, the Raman bands peak at 69 and
Fig. 3. Micro-Raman spectra from the Bi powder and Bi core in fiber.
93 cm−1, which can be assigned to the Eg and to the A1g first-order Raman modes of semimetallic bismuth [17]. It is worth noting that the fiber core shows the very similar Raman spectra to those of the Bi powder, indicating high degree of crystallinity and phase purity in Bi core. The EPMA, XRD, and micro-Raman spectra showed that little oxygen diffused into the core region due to the fibers drawn at relative lower temperature. 4. Discussion The challenge to integrate functional materials into multimaterial
Fig. 1. (a) Electron image of the Bi core fiber in cross section, (b)–(d) the EPMA images of the fiber in local cross section.
309
Materials Letters 186 (2017) 308–310
G. Tang et al.
fibers are the melting point and volatilization temperature of core material, heating rate, draw temperature, draw speed, core to clad ratio, and the coefficients of thermal expansion (CTE) of the materials and their chemical compatibilities [10,16,18]. The melting point and boiling point of Bi are 271.5 and 1564 °C, respectively. And the multimaterial fibers were drawn at 860 °C, which is higher than the melting point of Bi but lower than its boiling point. Therefore, the glass cladding can be directly drawn into fibers where the core precursor phase is molten, which goes “along for the ride” and ultimately solidified as the fibers cool [9]. The magnitude of the residual stresses in the as-drawn fibers is due to the unmatched CTE between glass cladding and core material. And the large residual stresses in the fibers will cause significant cracking and fiber breakage. The CTE of the Bi and silicate glass cladding are 1.1×10−4 and 3.3×10−6 K−1, respectively. It was found that smaller core to glass cladding ratios tended to reduce the tendency of glass cracking [16]. What is more, the raise of heating temperature was kept slow and gradation.
Distinguished Young Scientists (61325024), the High-level Personnel Special Support Program of Guangdong Province (2014TX01C087), Fundamental Research Funds for the Central Universities (2015ZP019), the Science and Technology Project of Guangdong (2015B090926010), China State 863 Hi-tech Program (2014AA041902) and NSFC (61535014 and 51302086). References [1] M.A. Schmidt, A. Argyros, F. Sorin, Adv. Opt. Mater. 4 (2016) 13. [2] G. Tao, A.F. Abouraddy, A.M. Stolyarov, Y. Fink, Multimaterial fibers. In: Lab-onFiber Technology, Springer International Publishing, 2015. pp. 1–26. [3] P.J.A. Sazio, A. Amezcua-Correa, C.E. Finlayson, J.R. Hayes, T.J. Scheidemantel, N.F. Baril, B.R. Jackson, D.J. Won, F. Zhang, E.R. Margine, V. Gopalan, V.H. Crespi, J.V. Badding, Science 311 (2006) 1583. [4] J. Ballato, T. Hawkins, P. Foy, R. Stolen, B. Kokuoz, M. Ellison, C. McMillen, J. Reppert, A.M. Rao, M. Daw, S.R. Sharma, R. Shori, O. Stafsudd, R.R. Rice, D.R. Powers, Opt. Express 16 (2008) 18675. [5] P. Dragic, T. Hawkins, P. Foy, S. Morris, J. Ballato, Nat. Photonics 6 (2012) 629. [6] G. Tang, Q. Qian, X. Wen, X. Chen, W. Liu, M. Sun, Z. Yang, Opt. Express 23 (2015) 23624. [7] A. Tuniz, K.J. Kaltenecker, B.M. Fischer, M. Walther, S.C. Fleming, A. Argyros, B.T. Kuhlmey, Nat. Commun. 4 (2013) 2706. [8] H.W. Lee, M.A. Schmidt, R.F. Russell, N.Y. Joly, H.K. Tyagi, P. Uebel, P.S.J. Russell, Opt. Express 19 (2011) 12180. [9] G. Tang, Q. Qian, X. Wen, G. Zhou, X. Chen, M. Sun, D. Chen, Z. Yang, J. Alloy. Compd. 633 (2015) 1. [10] S. Morris, J. Ballato, Bull. Am. Ceram. Soc. 92 (2013) 24. [11] A.C. Peacock, J.R. Sparks, N. Healy, Laser Photonics Rev. 8 (2014) 53. [12] A.C. Peacock, U.J. Gibson, J. Ballato, Adv. Phys.: X 1 (2016) 1. [13] D. Homa, G. Pickrell, G. Kaur, Mater. Lett. 121 (2014) 101. [14] C. Shekhar, A.K. Nayak, Y. Sun, M. Schmidt, M. Nicklas, I. Leermakers, U. Zeitler, Y. Skourski, J. Wosnitza, Z. Liu, Y. Chen, W. Schnelle, H. Borrmann, Y. Grin, C. Felser, B. Yan, Nat. Phys. 11 (2015) 645. [15] F.Y. Yang, K. Liu, K. Hong, D.H. Reich, P.C. Searson, C.L. Chien, Science 284 (1999) 1335. [16] D. Homa, G. Kaur, G. Pickrell, B. Scott, C. Hill, Mater. Lett. 133 (2014) 135. [17] K. Trentelman, J. Raman Spectrosc. 40 (2009) 585. [18] A.F. Abouraddy, M. Bayindir, G. Benoit, S.D. Hart, K. Kuriki, N. Orf, O. Shapira, F. Sorin, B. Temelkuran, Y. Fink, Nat. Mater. 6 (2007) 336.
5. Conclusions In conclusion, a new kind of multimaterial fibers with Bi core and silicate glass cladding was fabricated by a molten core method. The Bi core was found to be highly high degree of crystallinity and phase purity. Fiber optic sensing technologies stand to benefit from the pursuit of all-fiber optoelectronics. This study constitutes a proof-ofconcept that magnetic fiber optic sensors require the use of a high magnetoresistance material of Bi can be incorporated into fibers by using conventional fiber fabrication techniques, which is significant to the field of multimaterial fibers. Acknowledgments This research was supported by China National Funds for
310