LPI in pulsed laser space communications

The use of space optics with lightwave beams is being considered for various types of long range communication links. Most of these links are being designed with pulsed laser transmissions, usually in the form of a coded pulse position modulated (PPM) format. Closely associated with the design of the communication link itself may be a corresponding requirement for LPI (low probability of intercept). This occurs when an intercepting optical receiver is present to determine the source location by interrogating the light field. This paper formulates a basic LPI study for a pulsed laser PPM optical link with a co-located direct detection intercepting receiver. The latter is considered to be a form of optical radiometer using continuous threshold testing to detect the presence of the transmitting laser.