This paper presents a method of simulating various noise sources in a Weapons Fire Simulator System which has been modeled as an Optical Communications Channel. This Weapons Fire Simulator System is composed of laser transmitters mounted on weapons that fire blank cartridges, and laser receivers mounted on targets. The laser transmitter sends out "kill" beam pulses to the target whenever blank cartridges are fired. Detection of these pulses at the target signifies a "hit." The entire system along with the optical communication channel is simulated in a general-purpose computer program called SCEPTRE. This analysis package is an efficient means of modeling the communication channel characteristics and determining signal-to-noise ratios as functions of various electrical and physical parameters. Also the SCEPTRE program is a versatile tool for circuit noise calculations.¹ The main advantage is a single SCEPTRE run computes the total noise output from a large number of noise sources distributed throughout the circuit.