Rapid and precise absolute distance measurements at long range

• Published in: Nature photonics Vol. 3; no. 6; pp. 351 - 356
• Main Authors: Coddington, I, Newbury, N. R, Swann, W. C, Nenadovic, L
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 01.06.2009; Nature Publishing Group
• Subjects: Applied and Technical Physics; Exact sciences and technology; Fiber lasers; Fundamental areas of phenomenology (including applications); Lasers; Measurements common to several branches of physics and astronomy; Metrology, measurements and laboratory procedures; Optical elements, devices, and systems; Optics; Physics; Physics and Astronomy; Quantum Physics; Reflectors, beam splitters, and deflectors; Remote sensing; Spatial dimensions (e.g.: position, lengths, volume, angles, displacements, including nanometer-scale displacements); Laser ranging; Multimode laser; Reflectors; Multifrequency laser; Measuring methods; Time-of-flight method; Distance measurement; Manufacturing; Remote sensing; Fiber lasers
• ISSN: 1749-4885; 1749-4893
• DOI: 10.1038/nphoton.2009.94

The ability to determine absolute distance to an object is one of the most basic measurements of remote sensing. High-precision ranging has important applications in both large-scale manufacturing and in future tight formation-flying satellite missions, where rapid and precise measurements of absolute distance are critical for maintaining the relative pointing and position of the individual satellites. Using two coherent broadband fibre-laser frequency comb sources, we demonstrate a coherent laser ranging system that combines the advantages of time-of-flight and interferometric approaches to provide absolute distance measurements, simultaneously from multiple reflectors, and at low power. The pulse time-of-flight yields a precision of 3 µm with an ambiguity range of 1.5 m in 200 µs. Through the optical carrier phase, the precision is improved to better than 5 nm at 60 ms, and through the radio-frequency phase the ambiguity range is extended to 30 km, potentially providing 2 parts in 10 13 ranging at long distances. Using two coherent broadband fibre-laser frequency comb sources, a coherent laser ranging system for absolute distance measurements is demonstrated. Its combination of precision, speed and long range may prove particularly useful for space-based sciences.