In a system for covert sensing and communications a broadband light source is encoded using spread spectrum waveform coding to spread a narrow-band signal over frequency. The modulated broadband light is suitably hidden in additional noise and then split into two portions, a first portion of which illuminates a target, and a second portion of which is delayed and provided as a local oscillator. Light reflected from the target is combined with the local oscillator, detected using heterodyne, homodyne or quasi-homodyne techniques, demodulated and decoded to estimate the phase of the reflected light relative to the transmitted light to provide fine range estimates for the target. Waveform coding allows for time-correlation of the transmitted and received coded waveforms to provide improved resolution for adjusting the delay of the local oscillator to improve the detection schemes. The waveform coding also provides a covert communications channel.