Demonstration of 16-channel multiple-access analog optical TDM with 10 ps channel spacing

Many high-bandwidth analog communication systems require the processing of a large number of analog signals such as CATV distribution networks and antenna routing subsystems. Fiber optics technology has the capability to meet the requirements of these applications. Thus far, the vast majority of research on fiber-optic analog communications has concentrated on the modulation of continuous wave (CW) lasers for encoding data, such as sub-carrier multiplexing (SCM). However, since the signals are multiplexed and demultiplexed in the electrical domain, the maximum number of channels is limited in such a system due to intermodulation distortion caused by nonlinearities in the electrical-optical-electrical conversion process. In contrast, the techniques presented in the work are based on the multiplexing and demultiplexing of signals in the optical domain, thereby reducing nonlinear interactions between channels. In our approach, each analog signal is encoded as an envelope onto an optical pulse train. By using ultrashort optical pulses to sample the analog waveforms, multiple channels can be interleaved and combined resulting in TDMA frames of pulsed analog data. The individual channels can then be extracted from the aggregate pulse stream with the use of an ultrafast optical gating device, such as the terahertz optical asymmetric demultiplexer.