The development of optical reflectometers with a spatial resolution in the submillimeter range is reviewed. Optical time-domain reflectometers (OTDRs) and optical low-coherence reflectometers (OLCRs) for nondestructive diagnostics of waveguide devices are discussed. Techniques, system performances, and experimental results are discussed for OTDRs and for OLCRs. Fields of applications for these techniques are indicated, and some preliminary conclusions are presented. A dynamic range of approximately 100 dB and a spatial resolution in the range of 10-60 mu m were achieved with both types of reflectometers. Nondestructive diagnostics on waveguide components and integrated optics circuits are feasible at these performance levels. >