/usr/share/xfig/Libraries/Optics/ is in xfig-libs 1:3.2.6a-1.
This file is owned by root:root, with mode 0o755.
..
/usr/share/xfig/Libraries/Optics/Fiber/
/usr/share/xfig/Libraries/Optics/Fiber/collimator.fig
/usr/share/xfig/Libraries/Optics/Fiber/coupler_large.fig
/usr/share/xfig/Libraries/Optics/Fiber/coupler_small.fig
/usr/share/xfig/Libraries/Optics/Fiber/detector.fig
/usr/share/xfig/Libraries/Optics/Fiber/fiber_straight.fig
/usr/share/xfig/Libraries/Optics/Lens/
/usr/share/xfig/Libraries/Optics/Lens/asheric_1.fig
/usr/share/xfig/Libraries/Optics/Lens/asperic_2.fig
/usr/share/xfig/Libraries/Optics/Lens/biconvex_medium.fig
/usr/share/xfig/Libraries/Optics/Lens/biconvex_strong.fig
/usr/share/xfig/Libraries/Optics/Lens/biconvex_weak.fig
/usr/share/xfig/Libraries/Optics/Lens/convexconcave.fig
/usr/share/xfig/Libraries/Optics/Lens/planconcave_medium.fig
/usr/share/xfig/Libraries/Optics/Lens/planconcave_weak.fig
/usr/share/xfig/Libraries/Optics/Lens/planconvcave_strong.fig
/usr/share/xfig/Libraries/Optics/Lens/planconvex_medium.fig
/usr/share/xfig/Libraries/Optics/Lens/planconvex_strong.fig
/usr/share/xfig/Libraries/Optics/Lens/planconvex_weak.fig
/usr/share/xfig/Libraries/Optics/Mirror/
/usr/share/xfig/Libraries/Optics/Mirror/concave_medium.fig
/usr/share/xfig/Libraries/Optics/Mirror/concave_strong.fig
/usr/share/xfig/Libraries/Optics/Mirror/flat.fig
/usr/share/xfig/Libraries/Optics/Mirror/flat_piezo.fig
/usr/share/xfig/Libraries/Optics/README
/usr/share/xfig/Libraries/Optics/beam.fig
/usr/share/xfig/Libraries/Optics/beamsplitter_cube.fig
/usr/share/xfig/Libraries/Optics/detector.fig
/usr/share/xfig/Libraries/Optics/faraday_isolator.fig
/usr/share/xfig/Libraries/Optics/grating.fig