Method and apparatus for coherently processing signals from incoherent sources including laser signals

[0021] Referring now to the drawings, wherein like reference numerals refer to like components throughout, FIG. 1 is broadly illustrative of a block diagram of a linear frequency modulated (chirp) laser radar system in accordance with the subject invention that includes a stable optical reference oscillator (SORO) 10 which is used as a narrow bandwidth (BW) local oscillator and is comprised of a low power, CW source of coherent optical radiation which is used as a phase reference for a pair of optical transmit and deramp lasers 12 and 14. A transmit signal consisting of a train of laser pulses, each having a respective random initial phase, is transmitted and received from a target, not shown, via a transmit / receive (T / R) optics subassembly 16. A sample of the incoherent pulse signal from the transmit laser 12 is mixed, i.e. heterodyned, in an optical signal mixer 18 with the SORO 10 providing an output of a phase difference signal corresponding to the phase difference between the