5-Mbit/s cat’s-eye modulating retroreflectors

avid Klotzkin he University of Cincinnati epartment of Electrical and Computer Engineering and Computer Science .O. Box 210030 incinnati, Ohio 45221-0030 Abstract. Modulating retroreflectors MRRs couple passive optical retroreflectors with electro-optic modulators to allow free-space optical communication with a laser and pointing-acquisition-tracking system required on only one end of the link. Recently, MRR using multiple quantum well MQW modulators have been demonstrated using a large-area MQW placed in front of the aperture of a corner cube. For a MQW modulator, the maximum modulation rate can range into the gigahertz, limited only by the RC time constant of the device. Most MRR systems have used corner-cube retroreflectors with apertures of about 1 cm, which require large, and hence high-capacitance, modulators. Thus data rates exceeding a few megabits per second are not possible. We describe a new kind of MQW MRR that uses a cat’s-eye retroreflector with the MQW in the focal plane of the cat’s-eye. This system decouples the size of the modulator from the size of the optical aperture and allows much higher data rates. A 45-Mbit/s free space link over a range of 7 km is demonstrated. © 2007 Society of Photo-Optical Instrumentation Engineers. DOI: 10.1117/1.2789634