Abstract
Single mode fibers are used for sensing when extreme sensitivity is required or when a well defined polarization of light is needed at a remote sensing point. Most sensors which use single mode fibers are of the intrinsic type (i.e. the action of the measurand on the light occurs within the fiber itself). The sensitivity advantage of single mode fibers arises because they permit the user to construct guided wave interferometers directly from the fiber itself so as to measure small phase changes in light transmitted through the measuring region. This is achieved by comparing the phase of a light wave which has traversed a sensing path with the phase of another light wave originating from the same source but arriving via a protected, reference path. The phase difference can be measured with a sensitivity of ~10−6 of a wavelength [1] and the pathlength for the measuring interaction can be millions of wavelengths long. This leads to a possible measurement resolution for the optical path of one in 1012. Simultaneously, the absence of free space optical paths between sources and detectors eliminates slow alignment drifts which could easily occur if bulk-optical interferometers had been used. In practice, single mode fiber sensors tend to need very stable, highly coherent sources with low phase noise in order to gain full advantage of their potential sensitivity. When such sources are used, absolute calibration of phase difference is normally not possible and a range limit arises from the periodic nature of the interferometer output. These points will be explained later in this chapter. In published research, both of these problems have been avoided by using sources emitting in a broad wavelength range, with some compromise regarding the ultimate sensitivity achievable with any particular sensor. The concluding part of the chapter will be devoted to such devices. Another important point to understand is that this type of sensor ultimately measures optical pathlength. Anything which changes the pathlength will therefore produce a signal. Since there is a multitude of effects which can affect the optical pathlength through a fiber, great care must always be taken to reduce or to compensate for these unwanted changs.
Keywords
Single Mode Fiber Optical Fiber Sensor Fiber Optic Gyroscope Phase Bias Sagnac InterferometerPreview
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References
- 1.Jackson, D. A., Dandridge, A. and Sheem, S. K. (1980) Measurement of small phase shifts using a single mode optical fibre interferometer. Optics Lett., 5, 139.ADSCrossRefGoogle Scholar
- 2.Tatam, R. P., Pannell, C. N., Jones, J. D. C. and Jackson, D. A. (1987) Full polarisation state control utilising linearly birefringent monomode optical fibre. J. Lightwave Technol., LT-5(7), 980.Google Scholar
- 3.Tolansky, S. (1973) An Introduction to Interferometey. Longman, London.Google Scholar
- 4.Petuchowsky, S. J., Giallorenzi, T. G. and Sheem, S. K. (1981) A sensitive fibre optic Fabry Perot interferometer. IEEE J. Quant. Electron., QE-17, 2168.Google Scholar
- 5.Kersey, A. D., Jackson, D. A. and Corke, M. (1983) A simple fibre Fabry Perot sensor. Optics Commun., 45, 71.ADSCrossRefGoogle Scholar
- 6.Stokes, L. F., Chodorow, M. and Shaw, H. J. (1983) Sensitive all-single-mode-fiber resonant ring interferometer. IEEE J. Lightwave Technol., LT-1, 110.Google Scholar
- 7.Meltz, G., Morey, W. W. and Glenn, W. H. (1989) Formation of Bragg gratings in optical fibers by a transverse holographic method. Optics Leu., 14, 823.ADSCrossRefGoogle Scholar
- 8.Yariv, A. (1975) Quantum Electronics, 2nd edn., Wiley, London.Google Scholar
- 9.Jackson, D. A., Priest, R., Dandridge, A. and Tveten, A. B. (1980) Elimination of drift in a single mode optical fibre interferometer using a piezoelectrically stretched coiled fibre. Appl. Optics, 19, 2926.ADSCrossRefGoogle Scholar
- 10.Fritsch, K. and Adamasky, G. (1981) Simple circuit for feedback stabilization of a single mode optical fibre interferometer. Rev. Sci. Instrum., 52, 996.ADSCrossRefGoogle Scholar
- 11.Dandridge, A., Tveten, A. B. and Giallorenzi, T. G. (1982) Homodyne demodulation scheme for fibre-optic sensors using phase generated carrier. IEEE J. Quant. Electron., QE-18, 1647.Google Scholar
- 12.Sheem, S. K., Giallorenzi, T. G. and Koo, K. P. (1982) Optical techniques to solve the fading problem in fibre interferometers. Appl. Optics, 21, 689.ADSCrossRefGoogle Scholar
- 13.Kersey, A. D., Jackson, D. A. and Corke, M. (1983) Demodulation scheme for interferometric sensors employing laser frequency switching. Electron. Lett., 19, 102.CrossRefGoogle Scholar
- 14.Koo, K. P., Tveten, A, B. and Dandridge, A. (1982) Passive stabilisation scheme for fibre interferometers using (3 x 3) fibre directional couplers. Appl. Phys. Lett., 41, 616.Google Scholar
- 15.Cole, J. H., Danver, B. A. and Bucaro, J. A. (1982) Synthetic heterodyne interferometric demodulation. IEEE J. Quant. Electron., QE-18, 694.Google Scholar
- 16.Jackson, D. A., Kersey, A. D., Corke, M. and Jones, J. D. C. (1982) Pseudo-heterodyne detection scheme for optical interferometers. Electron. Lett., 18, 1081.CrossRefGoogle Scholar
- 17.Voges, E., Ostwald, O., Schick, B. and Neyer, A. (1982) Optical phase and amplitude measurements by single sideband homodyne detection. IEEE. J. Quant. Electron., QE-18. 124.Google Scholar
- 18.Kim, B. Y. and Shaw, H. J. (1984) Phase reading all fiber-oplic gyroscope. Optics Lett., 9, 378ADSCrossRefGoogle Scholar
- 19.Leilabadv, P A., Jones, J. D. C., Corke, M. and Jackson, D. A. (1986) J. Phys. E: Sci. Instrum., 19, 143.ADSCrossRefGoogle Scholar
- 20.Webb, D. J. Jones, J. D. C., Taylor, R. M. and Jackson, D. A. (1988) Extended range monomode fibre-optic sensors: spectral and polarisation techniques. Int. J. Opto-electron.,3(3), 213.Google Scholar
- 21.Hocker, G. B. (1979) Fiber-optic sensing of pressure and temperature. Appl. Optics, 18 (9), 1445.ADSCrossRefGoogle Scholar
- 22.Giallorenzi, T. G., Bucaro, J. A., Dandridge, A. et al. (1982) Optical fiber sensor technology. IEEE J. Quant. Electron., QE-18(4), 626.Google Scholar
- 23.Rao, Y. J. and Jackson, D. A. (2000) Principles of Fiber-optic Interferometry, Optical Fiber Sensor Technology 1, Kluwer Academic Publishers, The Netherlands.Google Scholar
- 24.Kumagai, T., Kajioka, H., Ohnuki, W., Akiyama, M. and Saito, S. (1999), Industrial applications of Fiber Optic Gyroscopes, in 13th International Conference on Optical Fiber Sensors, eds. B.Y.Kim and K.Hotate, Proc. SPIE 3746, 64–70.Google Scholar
- 25.Dagenais, D. M., Goldberg, L., Moeller, R. P. and Burns, W. K. (1999), Wavelength stable, high power amplified superfluorescent source for gyroscope application, in 13th International Conference on Optical Fiber Sensors, eds. B.Y.Kim and K.Hotate, Proc. SPIE 3746, 86–89.Google Scholar
- 26.Lefevre, H. (1993) The fiber optic gyroscope, Artech House Inc., Norwood, MA, USAGoogle Scholar
- 27.Dyott, R. B. (1978) The fibre optic Doppler anemometer. IEE J. Microw. Optics Acoust., 2, 13.ADSCrossRefGoogle Scholar