Novel approaches to optical reflectometry

The author reviews the fundamentals of optical reflectometry, including the standard optical time-domain reflectometry (OTDR) measurement. Some novel reflectometry schemes are described, including a spread-spectrum approach to long-range OTDR, as well as new optical frequency-domain reflectometry (OFDR) techniques that have proven useful for high-resolution measurements. These novel reflectometry techniques are suitable for testing both fiber links and small components. The spread-spectrum technique allows improved dynamic range without sacrificing resolution. High-speed modulators and detectors now allow the extension of OFDR techniques to high frequencies. Resulting measurements show a large dynamic range and resolution better than 4 mm.>