s_{D_2E}(t).\end{aligned}$$ Furthermore we see that the long wavelength (LW) limit defined as the leading $x$ term of the response (\[eq:sED2\]) is given by $$\begin{aligned}
\label{eq:sedlw}
s_{ED}^{LW}(t) & = & F^{s}({\bf n}_{ED})\,
h_{s}^{0}\,\cos{\left[ \omega\left(t - \frac{{{\boldsymbol \Omega}}\cdot{\bf x}_{E}}{{\rm v}}\right) + \phi_{0} \right]}\end{aligned}$$ so the corresponding Michelson interferometer $M^{LW}$ will not discern $h^{s}$, $h^{st}$ and $h^{sl}$ signals whatever orientation of the two arms ${\bf n}_{ED_1}$ and ${\bf n}_{ED_2}$ is (note that the same is true for some other responses e.g. the Sagnac interferometer $S(t)=s_{ED_1}(t-2L) + s_{D_1D_2}(t-L) + s_{D_2E}(t)- s_{ED_2}(t-2L) - s_{D_2D_1}(t-L) - s_{D_1E}(t)$). However beyond the LW limit the responses of the Michelson interferometers $M$ are different due to the orientation–dependent higher frequency terms which potentially enable to discriminate between the modes. On the other hand the difference between ${\rm v}=1$ and ${\rm v}\neq 1$ case shows up already in the LW limit, for instance, in the massive Brans-Dicke theory as the corrections $\sim{{\boldsymbol \Omega}}\cdot{\bf x}_{E}\left(\frac{m}{\omega}\right)^2$ in the signal’s phase.

Summary
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The analysis of the response of the laser interferometer to passing gravitational waves is a starting point in the gravitational waves detection experiments. Especially at the present moment of awaiting the first detection by the advanced detectors there is a 