Abstract
A highly sensitive and compact cross-correlator in which an Si avalanche photodiode (APD) is used as a two-photon absorber is described, which was developed for the measurement of picosecond-pulse transmission characteristics at 1550 nm. A 10 GHz, 1.7 ps pulse under test is generated from an external-cavity modelocked semiconductor laser, and is transmitted through an 80 km long dispersion-shifted fibre. A 200 fs sampling pulse is obtained from the pulse under test by pulse compression. An Si APD is used as a two-photon absorber for the cross-correlation measurement of the transmitted pulse waveform. The asymmetric pulse-waveform distortion stemming from the dispersion slope is clearly detected by the system.