An optical communication module having a roughened bottom of a silicon bench
for
suppressing optical crosstalk. The roughened bottom prevents stray laser beams
from reflecting toward a photodiode. The roughened bottom is further covered with
a photoabsorbent resin, pigment or adhesive for absorbing the stray laser beams
at a bottom. A cladding of a lightwaveguide are narrowed and are painted with a
photoabsorbent resin, pigment or adhesive for absorbing horizontally stray beams
propagating in the cladding.
