The Dense Optical Interface Module (DOIM) is a byte-wide optical
link developed for the Run II upgrade of the CDF silicon tracking system
[1].  The module consists of a transmitter with a laser-diode array for
conversion of digitized detector signals to light outputs, a 22 m optical
fiber ribbon cable for light transmission, and a receiver converting the
light pulses back to electrical signals.  We report on the design feature,
characteristics, and radiation tolerance.