Linear measurement of weak 1.57 mu m optical pulse train by heterodyne autocorrelation

A technique for measuring optical pulses, using heterodyne autocorrelation rather than a nonlinear process, is proposed. This method gives not only the pulse width, but also information about optical phase in a simple way. Practical measurement is demonstrated with linearly chirped weak optical pulse train from an actively model-locked external-cavity semiconductor laser. Pulse width and chirp are quantified. (C) 1996 American Institute of Physics.