@staticmethod
def calc_delta(beta_01, beta_02):
    """Calculate the measure of asymmetry for the parameters given
        for two waveguides. [8]_

        Parameters
        ----------
        beta_01 :
            The first term of the propagation constant of the first
            waveguide. :math:`[km^{-1}]`
        beta_02 :
            The first term of the propagation constant of the second
            waveguide. :math:`[km^{-1}]`

        Returns
        -------
        :
            Value of the asymmetry measure. :math:`[km^{-1}]`

        Notes
        -----

        .. math:: \\delta_{a12} = \\frac{1}{2} (\\beta_{01} - \\beta_{02})

        References
        ----------
        .. [8] Govind Agrawal, Chapter 2: Fibers Couplers,
           Applications of Nonlinear Fiber Optics (Second Edition),
           Academic Press, 2008, Page 57.

        """
    return 0.5 * (beta_01 - beta_02)
