Appropriate signal levels must be maintained in any digital optical system
that uses signal level thresholds to encode transmitted information.
Usually a high-level signal represents a logic 1 and a low-level signal
represents a logic 0. In these systems the device characteristics of
importance are power loss and cross talk. Power loss quantifies the
attenuation of optical power in devices. Cross talk represents the
addition of extraneous optical power to signals transmitted by these
devices. ...
...We present a graph-theoretic device model that permits efficient and
complete power analysis of optical systems. By tracking certain
power–related quantities, we can determine the worst–case operating
conditions of a system, and optimal logic thresholds can be computed.
The following discussion assumes either that loss and cross talk are
independent of wavelength or that linewidths are small enough to permit
these variations.