RF and Optical Techniques in Communication and Sensor Systems

Modern communication systems use hybrid techniques which involves both radio frequency (RF) and optical systems to transport information. Optical fiber is widely used to transport microwave signals because of its low loss and wide bandwidth. A hybrid communication system consists of a coaxial cable network and optical fiber network. Coaxial cables are used for RF communication whereas optical fibers for optical communication. This integrated RF and optical solution will give more speed, higher bandwidth and better mobility. RF to optical and optical to RF conversion are the key techniques used in any hybrid communication system. We have developed a multipurpose versatile device for hybrid communication system. Utilizing RF and optical techniques, a smart system was also developed for measurement and data transfer for health care applications.
Convergence of optical and RF communication systems result in the transmission of high speed microwave signals over optical fiber. Radio over fiber technologies supports the distribution of broadband RF/wireless signals. Present hybrid communication system is essentially a combination of RF coaxial cable network and optical fiber network. RF to optical and optical to RF conversion is the main techniques used in hybrid communication system. Objective of the present work is to develop RF to optical (optical transmitter) and optical to RF converter (Optical Receiver) modules for various applications in communication systems and its measurements. We have designed and developed a low cost intensity modulated transmitter using DFB laser for analog optical communication link. Optical receiver was developed with a high speed PIN photodiode. Appropriate impedance matching circuit is designed for both transmitter and receiver to achieve wide band frequency response. Transmitter and receiver were designed by modelling the circuits with microwave simulation tool called Ansoft designer. Performance of the system was verified by analyzing transmission and reflection characteristics.