Abstract: By using a non-linear guided wave optical time domain reflectometry (OTDR) technique, specific features of an optoelectronic integrated device may be probed by detecting the reflections and back-scattering of a short light pulse along a waveguide interconnect. An integrated optical correlator in the form of a second harmonic generation (SHG) waveguide and a photodetector array detects and measures ultra-short pulses for optical ranging. Used with a standard CCD camera, the direct images of the autocorrelation of compressed Nd-Yag pulses (FWHM of 5 ps) have been monitored at video rates. Used with a cooled CCD camera for OTDR, reflections from samples have been observed with an interfeature resolution of about 0.15 mm in GaAs, limited by the FWHM of the laser pulses. Appropriate signal processing can increase the positioning resolution to better than 50 .mu.m. Additional applications are demonstrated, including the monitoring of fiber lengths (to within 30 .mu.m in real time) and temperature sensing.