Page 214 - Instrumentation Reference Book 3E

198 Fiber optics in sensor instrumentation
optical edge filters (Figure 12.32) (Measures Boheim, G. and K. Fritsch, “Fiber-optic temperature
1992). The spectral properties of the edge filters sensor using a spectrum-modulated semiconductor
are chosen such that the filter operates in the etalon?” SPZE Fiber Optic and Laser Sensors V, 838,
middle of the extreme wavelength shift of the 238-246 (1987)
Bragg grating element and is placed immediately Boheim, G., K. Fritsch, and R. N. Poorman, “Fiber-
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put. Hence, as the Bragg wavelength shifts occur Bosselmann, Th. and R. Ulrich: ”High accuracy posi-
in response to the changing measurand, the tion-sensing with fiber-coupled white-light interfero-
amount of light intensity passed by the edge filter meters,” 2nd International Conference on Optical Fiber
also changes. For a linear filter function Sensors, Stuttgart, 361-364 (1984)
Change, Y. C. and T. M. Shay, “Frequency stabilisation
F(X) = A(X - XO) (12.60) of a laser diode to a Fabry-Perot interferometer,’‘
Opt. Eng., 27, 424427 (1988)
where A is the filter slope response and XO is the Chen, S., B. T. Meggitt, and A. J. Rogers, “Electronically
wavelength for which P(A) is zero. The ratio of the scanned white-light interferometry with enhanced
intensity passed by the fiiter IF to that of the total dynamic range,” Eec. Lett., 26, 1663-1664 (1990)
light intensity IT returned (reference signal) is Chen, S., A. W. Palmer, K.T.V. Grattan, and B. T.
given by: Meggitt, “Study of electronically-scanned optical-
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(12.61) 27, 1032-1304 (1991)
Chen, S., A. W. Palmer, K. T. V. Grattan, and B. T.
Meggitt, “An extrinsic optical fiber interferometric
assuming that the narrow backscattered Bragg sensor that uses multimode optical fiber: system and
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length ratiometric detection system with a Bragg Chen, S.. A. J. Palmer, K. T. V. Grattan, and B. T.
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When tested on a Lexan beam it was shown to Chen, S., B. T. Meggitt, K. T. V. Grattan, and A. W.
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