耐高温光纤光栅传感器的研究
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摘要
光纤布拉格光栅(Fiber Bragg Grating—FBG)传感器由于具有波长编码测量、抗电磁干扰、抗腐蚀、结构简单、尺寸小等优点而被广泛地应用于传感领域。然而，由于FBG并不是一个永久性的结构，当长时间工作在高温环境下时FBG会消失或被“洗掉”。因此，FBG传感器一般只能适用于较低温度的环境。为了将其应用扩展到高温领域，急需研制耐高温光纤光栅。
本论文采用高温退火工艺对特种掺杂光纤光栅进行热处理，利用杂质扩散效应造成纤芯中化学组分的空间周期性分布，由此形成纤芯折射率的空间周期性调制，成功地制作出化学组分光栅(chemical-composition grating—CCG)。由于其折射率调制是靠纤芯中化学组分的周期性分布形成的，因此这种光纤光栅具有极好的热稳定性，能够耐1000℃以上高温。在此基础上研究了CCG的温度响应和应变响应特性，研究了温度对CCG应变响应特性的影响。结果表明CCG在室温至1100℃范围内具有良好的温度响应特性，能够用于高温测量。CCG应变响应系数不随温度变化，其应变响应系数与普通光栅相当，能够满足高温热结构健康监测需要。
由于CCG的反射率比较低，一般不超过20％，本文还探讨了提高CCG反射率的方法和途径，研究了氢气饱和度、初始光栅强度和紫外激光脉冲能量对CCG反射率的影响。结果表明：要提高CCG反射率，应尽可能地提高氢气饱和度和初始光栅强度，而且在写制初始光栅时应采用尽可能小的激光能量。上述结论对提高CCG反射率具有重要指导意义。
Fiber Bragg grating (FBG) sensors have been widely used in sensing fields due to their distinguishing advantages, such as wavelength-encoded measurement, immunity to electromagnetic interference (EMI), light weight, simple for fabrication and so on. But FBG is not a permanent structure, it will be erased when operating for a long time under a sufficient high temperature. So they are only capable of operating in temperature range below 300℃. In order to extend FBG's sensing applications at higher temperature regions, the sensors with high temperature sustainability should be fabricated.
In this thesis we fabricated high-temperature-resistant chemical-composition gratings (CCGs) by writing FBGs in Ge/F codoped fiber with 193 nm eximer laser followed by special annealing procedure. The refractive index modulation of the CCGs is caused by a change in the chemical composition, hence these gratings show extremely high thermal stability at temperature up to 1100℃. The temperature and strain response of CCGs were investigated. The experimental results indicate that the temperature response of the CCGs has a fairly good performance. Further, the CCGs show strain coefficient that is about the same with normal FBGs. It is expected that the CCGs are suitable for health monitoring of the high temperature structure.
In order to increase the reflectivity of the CCGs, we also investigated effects of hydrogen concentration, initial grating strength and UV laser pulse energy on the reflectivity of the CCGs. It is found that improving the initial grating reflectivity, enhancing the hydrogen concentration or using lower pulse energy in the initial grating inscription help to increase the reflectivity of the CCGs.
本论文采用高温退火工艺对特种掺杂光纤光栅进行热处理，利用杂质扩散效应造成纤芯中化学组分的空间周期性分布，由此形成纤芯折射率的空间周期性调制，成功地制作出化学组分光栅(chemical-composition grating—CCG)。由于其折射率调制是靠纤芯中化学组分的周期性分布形成的，因此这种光纤光栅具有极好的热稳定性，能够耐1000℃以上高温。在此基础上研究了CCG的温度响应和应变响应特性，研究了温度对CCG应变响应特性的影响。结果表明CCG在室温至1100℃范围内具有良好的温度响应特性，能够用于高温测量。CCG应变响应系数不随温度变化，其应变响应系数与普通光栅相当，能够满足高温热结构健康监测需要。
由于CCG的反射率比较低，一般不超过20％，本文还探讨了提高CCG反射率的方法和途径，研究了氢气饱和度、初始光栅强度和紫外激光脉冲能量对CCG反射率的影响。结果表明：要提高CCG反射率，应尽可能地提高氢气饱和度和初始光栅强度，而且在写制初始光栅时应采用尽可能小的激光能量。上述结论对提高CCG反射率具有重要指导意义。
Fiber Bragg grating (FBG) sensors have been widely used in sensing fields due to their distinguishing advantages, such as wavelength-encoded measurement, immunity to electromagnetic interference (EMI), light weight, simple for fabrication and so on. But FBG is not a permanent structure, it will be erased when operating for a long time under a sufficient high temperature. So they are only capable of operating in temperature range below 300℃. In order to extend FBG's sensing applications at higher temperature regions, the sensors with high temperature sustainability should be fabricated.
In this thesis we fabricated high-temperature-resistant chemical-composition gratings (CCGs) by writing FBGs in Ge/F codoped fiber with 193 nm eximer laser followed by special annealing procedure. The refractive index modulation of the CCGs is caused by a change in the chemical composition, hence these gratings show extremely high thermal stability at temperature up to 1100℃. The temperature and strain response of CCGs were investigated. The experimental results indicate that the temperature response of the CCGs has a fairly good performance. Further, the CCGs show strain coefficient that is about the same with normal FBGs. It is expected that the CCGs are suitable for health monitoring of the high temperature structure.
In order to increase the reflectivity of the CCGs, we also investigated effects of hydrogen concentration, initial grating strength and UV laser pulse energy on the reflectivity of the CCGs. It is found that improving the initial grating reflectivity, enhancing the hydrogen concentration or using lower pulse energy in the initial grating inscription help to increase the reflectivity of the CCGs.
引文
[1] 何经雷．新型光敏光纤与耐高温布喇格光栅研究(博士论文)．杭州：浙江大学，2007．
[2] K.O. HilI, Y. Fujii, D.C. Johnson, and B.S. Kawasaki. Photosensitivity in optical fiber waveguides: Application to reflection filter fabrication. Applied Physics Letters, 1978, 32:647-649.
[3] B.S. Kawasaki, K.O. Hill, D.C. Johnson, and Y. Fujii. Narrow-band Bragg reflectors in optical fibers. Optical Letter, 1978, 3:66-68.
[4] G. Meltz, W.W. Morey, W.H. Glenn. Formation of Bragg gratings in optical fibers by a transverse holographic method. Optics Letters, 1989,14:823-825.
[5] K.O. Hill, B. Malo, F. Bilodeau, D.C. Johnson, and J. Albert. Bragg gratings fabricated in monomode photosensitive optical fibre by UV exposure through a phase mask Applied Physics Letters, 1993, 62:1035-1037.
[6] K.O. Hill, B. Malo, K.A. Vineberg, F. Bilodeau, D.C. Johnson, and Skinner. Efficient mode conversion in telecommunication fiber using externally written gratings. Electron Lett, 1990, 26:1270-1272.
[7] 宋世德．长周期光纤光栅的特性及传感应用研究(博士论文)．大连：大连理工大学，2006．
[8] A.M. Vengsarkar, P.J. Lemaire, J.B. Judkins, VBhatia, T. Erdogan and J. E.Sipe. Long-period fiber gratings as band-rejection filters. Conf. Optic. Fiber Commun., OFC'95, San Diego, CA, 1995.
[9] E.M. Dianov, VLKarpov, A.S. Kukov, O. LMedvedkov, A.M. Prokhorov, VN. Protopopov and S.A. Vasilev. Gain spectrum flattening of Erbium-doped fiber amplifier using long-period grating in photosensitivity and quadratic nonlinearity in glass wa}eguide fundamentals and applications. OSA Tech. Dig. Series, 1995, 22:14-17.
[10] A.M. Vengsarkar, J.R. Pedrazzani, J.B. Jukins P.J. Lemaire, M.S. Bergano, and C. K Davidson. Long period fiber grating based gain equalizers. Opt. Lett., 1996, 21:336-338.
[11] 刘海涛．光纤光栅制作工艺及其在光纤传感中的应用研究(博士论文)．上海：上海交通大学，2007．
[12] V Mirzrahi, T. Erdogan, D.J. Digiovanni, et al. Four channel fibre grating demultiplexer. Electron. Lett.,1994, 30:780.
[13] F. Bilodeau, D.C. Johnson, S. Theriault, et al.. An all-fiber dense wavelength-division multiplexer/demultiplexer using photoimprinted. Bragg gratings IEEE Photonics Technology Letters, 1995, 7(4):388.
[14] J.A.R.Williams, LBennion, K. Sugden and N.J. Dpran. Fibre dispersion compensation using a chirped in-fibre. Bragg grating Electron .Lett.,1994, 30:985.
[15] Peter, D.S. Onishchukov, G Hodel, W Weber, H. P. 570 fs pulses from a Pr~(3+) doped fibre laser modelocked by pump pulse induced cross-phase modulation. Electronics Letters Volume, 1994, 30(19):1595-1596.
[16] A. Othonos and KKalli. Fibre Bragg Gratings: Fundamentals and applications in telecommunication and sensing. Artech House, Boston, 1999.
[17] Guan BO, Tam HY, Tao XM, et al.. Highly stable fiber Bragg gratings writer in hydrogen-loaded fiber. IEEE PHOTONICS TECHNOLOGY LETTERS, 2000, 12 (10):1349-1351
[18] Guan BO, Tam HY, Lu C, et al.. Postfabrication wavelength trimming of fiber Bragg gratings written in H-2-loaded fibers. IEEE PHOTONICS TECHNOLOGY LETTERS, 2001, 13 (6): 591-593.
[19] Y. Shen, J. Xia, T. Sun and K. T. V. Grattan. High temperature sustainability of strong FBGs written into Sb/Ge co-doped photosensitive fiber — decay mechanisms involved during annealing. Optics Letters, 2004, 29:554-556.
[20] Y. Shen, J. Xia, T. Sun and K. T. V. Grattan. Photosensitive Indium doped germano-silica fiber for strong FBGs with high temperature sustainability. IEEE Photonic Tech. Lett., 2004, 16:1319-1321.
[21] Brambilla G, Rutt H. Fiber Bragg gratings with enhanced thermal stability. APPLIED PHYSICS LETTERS, 2002, 80(18):3259-3261.
[22]Fokine M. Thermal stability of chemical composition gratings in fluorine-germanium-doped silica fibers. OPTICS LETTERS, 2002, 27(12):1016-1018.
[23] Trpkovski S , Kitcher DJ, Baxter GW, et al.. High-temperrature-resistant chemical composition Bragg gratings in Er~(3+)-doped optical fiber. OPTICS LETTERS , 2005, 30(6): 607-609.
[24] D.L.Williams, B. J. Ainslie, J. R Armitage, J. R. Kashyap, and R. Campbell. Enhanced UV photosensitivity in boron codoped germanosilicate fibers. Electronics Letters,1993,29:45-47.
[25] M. M. Broer, R. L. Cone, J.R.Simpson. Ultraviolet-induced distributed-feedback gratings in Ce~(3+)-doped silica optical fibers. Optics Letter, 1991, 16:1391-1393.
[26] F. Bilodeau, D.C.Johnson, B.Malo, K. A. Vineberg, K. O. Hill, T.F.Morse, A. Kilian, and L.Reinhart. Ultraviolet-light photosensitivity in Er~(3+)-Ge-doped optical fiber. Optics Letters, 1990, 15:1138-1140.
[27] Atkins, R. M. Mizrahi, V. Erdogan, T. 248 nm induced vacuum UV spectral changes in optical fibre preform cores: support for a colour centre model of photosensitivity. Electronics Letters,1993, 29(4):385-387.
[28] R. M. Mizrahi, V. Erdogan, T. 248 nm induced vacuum UV spectral changes in optical fibre preform cores: support for a colour centre model of photosensitivity Atkins. Electronics Letters, 1993, 29(4):385-387.
[29] D. P. Hand, P. St. J. Russel. photoinduced refractive-index changes in germanosilicate fibers. Optics Letters, 1990, 15:102-104.
[30] C. Fiori and R. A. B. Devine. Ultraviolet irradiation induced compaction and photoetching in amorphous thermal SiO_2. Material Research Society Symposium Proceedings, 1986, 61:187-195.
[31] M. GSceats and S. B. Poole. Aust. An Ultra High Resolution Distributed Temperature Sensor. Conf.Opt. Fiber Technol., 1991, 302.
[32] F.P.Payne. Photorefractive gratings in single-mode optical fibers. Electronice Letters,1989, 25:498-499.
[33] N. M. Lawandy. Light induced transport and delocalization in transparent amorphous systems. Optics Communications, 1989, 74:180-184.
[34] Lemaire, P.J.Atkins, R. M. Mizrahi, V. Reed, W. A.. High pressure Hz loading as a technique for achieving ultrahigh UV photosensitivity and thermal sensitivity in GeO_2 doped optical fibres. Electronics Letters,1993, 29(13):1191 — 1193.
[35] F. Bilodeau, B. Malo, J.Albert, D.C.Johnson, and K. 0. Hill. High-return-loss narrowband all-fiber bandpass Bragg transmission filter. Opt.Lett.,1993, 18:953.
[36] B. J. Armitage, J. R. Kashyap, R.Campbell, R.Williams, D. L. Ainsfie. Enhanced UV photosensitivity in boron codoped germanosilicate fibres. Electronics Letters,1993, 29(1) :45.
[37] J.Albert, B. Malo, F. Bilodeau, D.C.Johnson, K. 0. Hill, Y. Hibino, and M. Kawachi. Photosensitivity in Ge-doped silica optical waveguides and fiber with 193nm Light from an ArF eximer laser. Optics Letter, 1994, 19:377-379.
[38] P. E. Dyer, R.J.Farley, R. Giedl, K.C.Byron, and D.Reid, Electron. High reflectivity fiber gratings produced by incubated damage using a 193nm ArF laser. Electronics Letters, 1994, 30:860-862.
[39] T. Erdogan, V. Mizrahi, P. J. Lemaire and D. Monroe. Decay of ultraviolet-induced fiber Bragg gratings. J. Appl. phys., 1994, 76:73-80.
[40] S. R. Baker, H. N. Rourke, V. Baker and D. Goodchild. Thermal decay of fiber Bragg gratings written in boron and germanium codoped silica fiber. IEEE J. Lightwave Technol., 1997, 15:1470-1477.
[41] S. Kannan, J.Z. Y. Guo and P. J. Lemaire. Thermal stability analysis of uv-induced fiber Bragg gratings. IEEE J. Lightwave Technol., 1997, 15:1478-1483.
[42] H. Patrick, S. L. Gilbert, A. Lidgard and M. D. Gallagher. Annealing of Bragg gratings in hydrogen-loaded optical fiber. J. Appl. Phys., 1995, 78:2940-2945.
[43] J. Rathje, M, Kristensen, and J. E. Pedersen. Continuous anneal method for characterizing the thermal stability of ultraviolet Bragg gratings. J. Appl. Phys., 2000, 88:1050-1055.
[44] M. Fokine. Formation of thermally stable chemical composition gratings in optical fibers. Journal of the Optical Society of America B-Optical Physics, 2002, 19(8) : 1759-1765.
[45] Michael Fokine. Underlying mechanisms, applications, and limitations of chemical composition gratings in silica based fibers. Journal of Non-Crystalline Solids,2004, 349:98-104.
[46] M. Fokine. Growth dynamics of chemical composition gratings in fluorine-doped silica optical fibers .Optical Letters, 2002, 27(22):1974-1976.
[47] R. H. Doremus, J.W.Mitchell, R. C. DeVries, R.W.Roberts, and P. Cannon. The diffusion of water in fused silica. Wiley, New York, 1969:667-673.
[48] J. Kirchhof, S. linger, H. J. Pissler, and B. Knappe. Hydrogen-induced hydroxyl profiles in doped silica layers. Optical Fiber Communication Conference, 1995, 8:WP9.
[49] R. H. Doremus. J.Mater. Diffusion of Water in Silica Glass. Journal of Materials Reserch, 1995, 10 (9):2379-2389.
[50] P. B. McGinnis and J. E. Shelby, Diffusion of Water in Vitreous Silica, J. Non-Cryst. Solids, 1994, 179: 185-193.
[51] Michael Fokine. Growth dynamics of chemical composition gratings in fluorine-doped silica optical fibers. Optics Letters, 2002, 27(22):1974-1976.
[52] Michael Fokine. Thermal stability of chemical composition gratings in fluorine-germanium-doped silica fibers. Optics Letters,2002, 27(12):1016-1018.
[53] W. Jost. in Diffusion in solids, Liquids, and Gases. E. Hutchinson, ed., 1952:32-46.
[2] K.O. HilI, Y. Fujii, D.C. Johnson, and B.S. Kawasaki. Photosensitivity in optical fiber waveguides: Application to reflection filter fabrication. Applied Physics Letters, 1978, 32:647-649.
[3] B.S. Kawasaki, K.O. Hill, D.C. Johnson, and Y. Fujii. Narrow-band Bragg reflectors in optical fibers. Optical Letter, 1978, 3:66-68.
[4] G. Meltz, W.W. Morey, W.H. Glenn. Formation of Bragg gratings in optical fibers by a transverse holographic method. Optics Letters, 1989,14:823-825.
[5] K.O. Hill, B. Malo, F. Bilodeau, D.C. Johnson, and J. Albert. Bragg gratings fabricated in monomode photosensitive optical fibre by UV exposure through a phase mask Applied Physics Letters, 1993, 62:1035-1037.
[6] K.O. Hill, B. Malo, K.A. Vineberg, F. Bilodeau, D.C. Johnson, and Skinner. Efficient mode conversion in telecommunication fiber using externally written gratings. Electron Lett, 1990, 26:1270-1272.
[7] 宋世德．长周期光纤光栅的特性及传感应用研究(博士论文)．大连：大连理工大学，2006．
[8] A.M. Vengsarkar, P.J. Lemaire, J.B. Judkins, VBhatia, T. Erdogan and J. E.Sipe. Long-period fiber gratings as band-rejection filters. Conf. Optic. Fiber Commun., OFC'95, San Diego, CA, 1995.
[9] E.M. Dianov, VLKarpov, A.S. Kukov, O. LMedvedkov, A.M. Prokhorov, VN. Protopopov and S.A. Vasilev. Gain spectrum flattening of Erbium-doped fiber amplifier using long-period grating in photosensitivity and quadratic nonlinearity in glass wa}eguide fundamentals and applications. OSA Tech. Dig. Series, 1995, 22:14-17.
[10] A.M. Vengsarkar, J.R. Pedrazzani, J.B. Jukins P.J. Lemaire, M.S. Bergano, and C. K Davidson. Long period fiber grating based gain equalizers. Opt. Lett., 1996, 21:336-338.
[11] 刘海涛．光纤光栅制作工艺及其在光纤传感中的应用研究(博士论文)．上海：上海交通大学，2007．
[12] V Mirzrahi, T. Erdogan, D.J. Digiovanni, et al. Four channel fibre grating demultiplexer. Electron. Lett.,1994, 30:780.
[13] F. Bilodeau, D.C. Johnson, S. Theriault, et al.. An all-fiber dense wavelength-division multiplexer/demultiplexer using photoimprinted. Bragg gratings IEEE Photonics Technology Letters, 1995, 7(4):388.
[14] J.A.R.Williams, LBennion, K. Sugden and N.J. Dpran. Fibre dispersion compensation using a chirped in-fibre. Bragg grating Electron .Lett.,1994, 30:985.
[15] Peter, D.S. Onishchukov, G Hodel, W Weber, H. P. 570 fs pulses from a Pr~(3+) doped fibre laser modelocked by pump pulse induced cross-phase modulation. Electronics Letters Volume, 1994, 30(19):1595-1596.
[16] A. Othonos and KKalli. Fibre Bragg Gratings: Fundamentals and applications in telecommunication and sensing. Artech House, Boston, 1999.
[17] Guan BO, Tam HY, Tao XM, et al.. Highly stable fiber Bragg gratings writer in hydrogen-loaded fiber. IEEE PHOTONICS TECHNOLOGY LETTERS, 2000, 12 (10):1349-1351
[18] Guan BO, Tam HY, Lu C, et al.. Postfabrication wavelength trimming of fiber Bragg gratings written in H-2-loaded fibers. IEEE PHOTONICS TECHNOLOGY LETTERS, 2001, 13 (6): 591-593.
[19] Y. Shen, J. Xia, T. Sun and K. T. V. Grattan. High temperature sustainability of strong FBGs written into Sb/Ge co-doped photosensitive fiber — decay mechanisms involved during annealing. Optics Letters, 2004, 29:554-556.
[20] Y. Shen, J. Xia, T. Sun and K. T. V. Grattan. Photosensitive Indium doped germano-silica fiber for strong FBGs with high temperature sustainability. IEEE Photonic Tech. Lett., 2004, 16:1319-1321.
[21] Brambilla G, Rutt H. Fiber Bragg gratings with enhanced thermal stability. APPLIED PHYSICS LETTERS, 2002, 80(18):3259-3261.
[22]Fokine M. Thermal stability of chemical composition gratings in fluorine-germanium-doped silica fibers. OPTICS LETTERS, 2002, 27(12):1016-1018.
[23] Trpkovski S , Kitcher DJ, Baxter GW, et al.. High-temperrature-resistant chemical composition Bragg gratings in Er~(3+)-doped optical fiber. OPTICS LETTERS , 2005, 30(6): 607-609.
[24] D.L.Williams, B. J. Ainslie, J. R Armitage, J. R. Kashyap, and R. Campbell. Enhanced UV photosensitivity in boron codoped germanosilicate fibers. Electronics Letters,1993,29:45-47.
[25] M. M. Broer, R. L. Cone, J.R.Simpson. Ultraviolet-induced distributed-feedback gratings in Ce~(3+)-doped silica optical fibers. Optics Letter, 1991, 16:1391-1393.
[26] F. Bilodeau, D.C.Johnson, B.Malo, K. A. Vineberg, K. O. Hill, T.F.Morse, A. Kilian, and L.Reinhart. Ultraviolet-light photosensitivity in Er~(3+)-Ge-doped optical fiber. Optics Letters, 1990, 15:1138-1140.
[27] Atkins, R. M. Mizrahi, V. Erdogan, T. 248 nm induced vacuum UV spectral changes in optical fibre preform cores: support for a colour centre model of photosensitivity. Electronics Letters,1993, 29(4):385-387.
[28] R. M. Mizrahi, V. Erdogan, T. 248 nm induced vacuum UV spectral changes in optical fibre preform cores: support for a colour centre model of photosensitivity Atkins. Electronics Letters, 1993, 29(4):385-387.
[29] D. P. Hand, P. St. J. Russel. photoinduced refractive-index changes in germanosilicate fibers. Optics Letters, 1990, 15:102-104.
[30] C. Fiori and R. A. B. Devine. Ultraviolet irradiation induced compaction and photoetching in amorphous thermal SiO_2. Material Research Society Symposium Proceedings, 1986, 61:187-195.
[31] M. GSceats and S. B. Poole. Aust. An Ultra High Resolution Distributed Temperature Sensor. Conf.Opt. Fiber Technol., 1991, 302.
[32] F.P.Payne. Photorefractive gratings in single-mode optical fibers. Electronice Letters,1989, 25:498-499.
[33] N. M. Lawandy. Light induced transport and delocalization in transparent amorphous systems. Optics Communications, 1989, 74:180-184.
[34] Lemaire, P.J.Atkins, R. M. Mizrahi, V. Reed, W. A.. High pressure Hz loading as a technique for achieving ultrahigh UV photosensitivity and thermal sensitivity in GeO_2 doped optical fibres. Electronics Letters,1993, 29(13):1191 — 1193.
[35] F. Bilodeau, B. Malo, J.Albert, D.C.Johnson, and K. 0. Hill. High-return-loss narrowband all-fiber bandpass Bragg transmission filter. Opt.Lett.,1993, 18:953.
[36] B. J. Armitage, J. R. Kashyap, R.Campbell, R.Williams, D. L. Ainsfie. Enhanced UV photosensitivity in boron codoped germanosilicate fibres. Electronics Letters,1993, 29(1) :45.
[37] J.Albert, B. Malo, F. Bilodeau, D.C.Johnson, K. 0. Hill, Y. Hibino, and M. Kawachi. Photosensitivity in Ge-doped silica optical waveguides and fiber with 193nm Light from an ArF eximer laser. Optics Letter, 1994, 19:377-379.
[38] P. E. Dyer, R.J.Farley, R. Giedl, K.C.Byron, and D.Reid, Electron. High reflectivity fiber gratings produced by incubated damage using a 193nm ArF laser. Electronics Letters, 1994, 30:860-862.
[39] T. Erdogan, V. Mizrahi, P. J. Lemaire and D. Monroe. Decay of ultraviolet-induced fiber Bragg gratings. J. Appl. phys., 1994, 76:73-80.
[40] S. R. Baker, H. N. Rourke, V. Baker and D. Goodchild. Thermal decay of fiber Bragg gratings written in boron and germanium codoped silica fiber. IEEE J. Lightwave Technol., 1997, 15:1470-1477.
[41] S. Kannan, J.Z. Y. Guo and P. J. Lemaire. Thermal stability analysis of uv-induced fiber Bragg gratings. IEEE J. Lightwave Technol., 1997, 15:1478-1483.
[42] H. Patrick, S. L. Gilbert, A. Lidgard and M. D. Gallagher. Annealing of Bragg gratings in hydrogen-loaded optical fiber. J. Appl. Phys., 1995, 78:2940-2945.
[43] J. Rathje, M, Kristensen, and J. E. Pedersen. Continuous anneal method for characterizing the thermal stability of ultraviolet Bragg gratings. J. Appl. Phys., 2000, 88:1050-1055.
[44] M. Fokine. Formation of thermally stable chemical composition gratings in optical fibers. Journal of the Optical Society of America B-Optical Physics, 2002, 19(8) : 1759-1765.
[45] Michael Fokine. Underlying mechanisms, applications, and limitations of chemical composition gratings in silica based fibers. Journal of Non-Crystalline Solids,2004, 349:98-104.
[46] M. Fokine. Growth dynamics of chemical composition gratings in fluorine-doped silica optical fibers .Optical Letters, 2002, 27(22):1974-1976.
[47] R. H. Doremus, J.W.Mitchell, R. C. DeVries, R.W.Roberts, and P. Cannon. The diffusion of water in fused silica. Wiley, New York, 1969:667-673.
[48] J. Kirchhof, S. linger, H. J. Pissler, and B. Knappe. Hydrogen-induced hydroxyl profiles in doped silica layers. Optical Fiber Communication Conference, 1995, 8:WP9.
[49] R. H. Doremus. J.Mater. Diffusion of Water in Silica Glass. Journal of Materials Reserch, 1995, 10 (9):2379-2389.
[50] P. B. McGinnis and J. E. Shelby, Diffusion of Water in Vitreous Silica, J. Non-Cryst. Solids, 1994, 179: 185-193.
[51] Michael Fokine. Growth dynamics of chemical composition gratings in fluorine-doped silica optical fibers. Optics Letters, 2002, 27(22):1974-1976.
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