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10.2. A Brief Review of Types of Fiber-Optic Sensors  579
       where A x and A y represent the amplitude for the x and y components,
       respectively, while d x and 6 y represent the phase for the x and y components,
       respectively. The transformation from one polarization state to another polar-
       ization state is represented by a 2 x 2 transformation matrix with complex
       components called the Jones matrix.
         On the other hand, in the Mueller calculus, the polarization state is
       represented by the Stokes vector, s = (s t,s 2, s 3, s 4) and transformation is
       represented by a 4 x 4 transformation matrix with real components called the
       Mueller matrix. The basic difference between the Jones calculus and the
       Mueller calculus is that in the Jones approach, all the elements can be complex
       numbers, while in the Mueller approach, all the elements are real numbers.
         Table 10.1 illustrates the polarization state expression in terms of Jones
       vectors and Mueller vectors. Table 10.2 illustrates the most commonly used
       polarization state transformation matrices in terms of Jones matrices and
       Mueller matrices.
         With the Jones and Mueller calculi, the output polarization state can be
       calculated from the input polarization state as well as the transformation
       matrix. Assume that the light passes through a series of optical elements
       consisting of polarizers and retarders. The output state can be obtained by
       sequentially multiplying the vector for the input state by the matrix represen-
       ting each optical element in the order that it encounters them. Mathematically,
       this can be written as
                              7 0 - M / M / _                        (10.6)


                                     Table 10.1
                                                                2
                                                 is
        Polarization for Light Vector E with E x = A xe'5\ £., = A ve >\ S = <5, — 6.., and A  —
                     a             x   x    y   y  ?   x   y ?
       Status of polarization      Jones vector       Stokes (or Mueller) vector
                                         li
                                      [A xe *~\              f  A 2
       Linear polarization:    Jones: a =                      2
                                         e
        transmission axis             L^y  \J       Mueller s- =  A  cos 2ff
                                                               2
        at angle 0 to x axis                                  /I  sin 20
                                                             1   o
                                           A   1             _  2
                                                               A
       Right { + ) and left (-)          V ~
                                          - / ^'^ ^
        circular polarization:  Jones, a =  ,4      Mueller: S =  0
                                       jl_ (? >(<5 JV ±rt/2)   0
       Ax = Ay = /l..\/2, <5 = ±7t/2
                                                                2
                                      _v''2                  _+/! _
                                          Mv
                                      fv4 e  l               " ^ + X? "
       Elliptical polarization  Jones: a =  x   y
                                                                2
                                       A,,e                    A  - A 2
                                      L   J
                                        *           Mueller: s =
                                                              2A^A V cos d
                                                             _2A xA y sin<5
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