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Interrogation Techniques for Fiber Grating Sensors and the Theory of Fiber Gratings
Published in Shizhuo Yin, Paul B. Ruffin, Francis T. S. Yu, Fiber Optic Sensors, 2017
In the scheme demonstrated by Kersey et al. [73], shown in Figure 7.34, the arrayed eight interferometric sensors were investigated in a ladder topology with 30-m fiber delay lines for separate sensors. Using a continuous wave (CW) 830-nm diode laser and an acousto-optic modulator, the PRBS was produced to be 31 bits (m = 5) in length with a single bit length of ~145 ns that matched the fiber delay line of 30 m. The measured sensitivity was ~100μ rad/Hz, and the cross-talk levels were determined to be ~60 dB.
Introduction
Published in Arthur H. Hartog, An Introduction to Distributed Optical Fibre Sensors, 2017
Multiplexed sensor systems exist in a variety of topologies. In a ladder topology (Figure 1.4b),a down‐lead fibre conveys the probe light past each of the sensors in turn, providing a fraction of the probe energy to each sensor. The modulated light from each sensor is collected by a return fibre and brought back to the interrogator. Alternatively, in a reflective topology (Figure 1.4c), the probe light travels to each of the sensors and a portion of its energy is modulated and reflected back towards the interrogator. These multiplexed arrangements are to be contrasted with the single‐point sensor (Figure 1.4a), where the sensor is connected directly to the interrogator using one or two fibres.
Two Decades of Multidimensional Systems Research and Future Trends
Published in Krzysztof Gałkowski, Jeff David Wood, Multidimensional Signals, Circuits and Systems, 2001
The presentation here has been exclusively in terms of transfer operators that provide the input/output description. A state-space description can also be pursued for which earlier results arc summarized in ((Bose 1982). Chapter 4) and recent documentations arc extensive (Galkowski 1947). (Obeist 1990). (Zerz & Oberst 1993). It was observed (Oberst 1498) that the solution in a special case of the Cauchy problem was given as early as 1910 in a book (Riquicr 1910). which interestingly contained the essence of the Gröbner basis algorithm not only for polynomials but even for differential operators with coefficients in the differential field of rational functions. An algebraic analysis of linear multidimensional systems has been conducted recently by J. F. Pommaret and A. Quadrat (personal correspondence with the second author. 1998) by exploiting the duality existing between the theory of differential modules and the formal theory of systems of partial differential equations. This module-theoretic approach, also adopted by Oberst in his seminal paper (Oberst 1990), though requiring considerable algebraic machineries, permit clarification and unification of existing tools in multidimensional systems theory. For example, the consequences of various notions of coprimcness (zero, minor, factor) in multivariate polynomial matrix algebra can be better understood by applying module theory. Of course, the prohlem of zero coprimcness and unimodular matrix completion is linked to the Quillen-Suslin proof (1976) of Scrrc's celebrated conjecture that projective modules over polynomial rings are free and the equivalence of minor and factor primeness when matrix elements arc drawn from the ring, гг], follows from the fact that a finitely generated module over such a ring is reflexive, or equivalently, is a second syzygy (Evans & Griffith 1985). The next major result appeared in the form of Susiin's Stability Theorem under which any square unimodular matrix with entries in a multivariate polynomial ring can be expressed as a product of elementary matrices. This result provides the machinery for biorthogonal multiband filter bank realization for perfect reconstruction using the ladder topology. The case when both
Nano-scale area-efficient Gm–C filters using MOS capacitors
Published in International Journal of Electronics Letters, 2019
The above values along with initial filter specifications are used in ‘Nuhertz filter solutions’ (Nuhertz Technologies, 2015) to evaluate the capacitors of the ladder topology as , , , and . For these specifications, the transfer function of the filter is also derived as