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QKD: Mostly finish sections except for offset gear mesh

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jaseg 2024-09-09 16:01:16 +02:00
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chapter-qkd/chapter.tex
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@ -1018,43 +1018,46 @@ perspectives, and Figure\ \ref{qkd_fig_lab_mesh_section} shows a section view.
mesh schema in Figure\ \ref{qkd_fig_offset_lab_schema}.}
\end{figure}
The offset labyrinth design already achieves a high level of security through its complex passthrough shape, but its
construction provides some challenges. First, with increasing offset, the step size of one mesh ring's diameter to the
next increases as well. Even if we only use, say, four mesh rings, this results in a large outer diameter. Second, fiber
passthrough in the plain offset configuration is possible, but the fiber must be wound in a spiral to pass the two
meshes' rings alternating from one side to the other because the side with more space alternates from ring to ring.
The offset labyrinth design already achieves a high level of security through its complex passthrough shape, but only
small offset distances are feasible since large offsets quickly lead to impractically large mesh sizes. Where the pitch
from one tab ring to the next is roughly constant in concentric labyrinth meshes, and determined only by clearances and
the amount of inter-mesh space necessary for power and data feedthroughs as well as mechanical stability. In offset
meshes, on the other hand, this pitch increases by the offset distance. Even for a small offset this quickly adds up to
an unwieldy total mesh size.
Both of these disadvantages can be worked around using a design where the two meshes interlock like gears. This does
mean that the two meshes' rotation must be synchronized, but it allows for a tighter spacing even when using an offset
design. Additionally, in a gear setup, the wide sides of the inter-mesh zones can be aligned to lie on the same side, so
fiber passthrough can be realized more easily without the need to spiral the fiber around the axes of rotation.
In this section, we conceptually introduce a solution to this problem that allows for larger offsets using a design
where the two meshes interlock like gears. This does mean that the two meshes' rotation must be synchronized, but it
increases the design space of offset labyrinth meshes. For instance, in a gear setup, the wide sides of the inter-mesh
zones can be aligned to lie on the same side, so fiber passthrough can be realized more easily even without the need to
spiral the fiber around the axes of rotation.
\subsection{Mesh synchronization}
For geared meshes to work, both speed and phase of the rotation of the two meshes must be synchronized to a small error.
In this setup, the mesh tabs act like gear teeth. Depending on the ratio between both meshes' tap counts, the two
meshes do not have to rotate at the same rate of rotation. Instead, harmonic ratios are possible.
meshes do not have to rotate at the same rate of rotation and harmonic ratios are possible. Additionally, unlike actual
gears which need to constantly maintain an area of contact, both co-rotating and counter-rotating setups are possible.
\begin{figure}
\centering
\subcaptionbox[Offset labyrinth mesh assembly render]{\figureattrib{render_side_1.png}}{\includegraphics[width=\textwidth]{\scaledgraphics{render_side_1.png}}}
\subcaptionbox[Offset labyrinth mesh assembly render]{\figureattrib{render_side_2.png}}{\includegraphics[width=\textwidth]{\scaledgraphics{render_side_2.png}}}
\subcaptionbox[Offset gear labyrinth mesh assembly render]{\figureattrib{render_side_1.png}}{\includegraphics[width=\textwidth]{\scaledgraphics{render_side_1.png}}}
\subcaptionbox[Offset gear labyrinth mesh assembly render]{\figureattrib{render_side_2.png}}{\includegraphics[width=\textwidth]{\scaledgraphics{render_side_2.png}}}
\caption{
Renderings of the complete offset labyrinth mesh assembly with interlocking labyrinth.
Renderings of the complete offset labyrinth gear mesh assembly.
}
\end{figure}
\begin{figure}
\centering
\includegraphics[width=\textwidth]{gear_plan_1.eps}
\caption[Offset overlapping gear mesh assmbly schema]{\figureattrib{gear_plan_1.svg}}
\caption[Offset gear mesh assmbly schema]{\figureattrib{gear_plan_1.svg}}
\end{figure}
\begin{figure}
\centering
\includegraphics[width=\textwidth]{gear_plan_2.eps}
\caption[Offset overlapping gear mesh schedule]{\figureattrib{gear_plan_2.svg}}
\caption[Offset gear mesh schedule]{\figureattrib{gear_plan_2.svg}}
\end{figure}
\section{Outlook}