Optical communication at the source bandwidth limit

Communicator bandwidth is referred to as the maximum rate at which temporally disjoint optical signals can be produced or detected. An optical communication system usually comprises a laser, a modulator, and a detector. The light is produced by a laser, temporally modulated by a modulator, transmitted through some medium, and temporally demodulated at the receiver. At present, the communication bandwidth tends to be limited by practical constraints on the modulation and detection bandwidths. It is shown that the constraints on the modulation and demodulation rates can be removed so as to obtain a laser bandwidth limited communication system. The two general principles of using low-duty-cycle ultrafast-pulse lasers and spatial modulation with time delays to achieve high modulation rates are demonstrated.