OPTICAL CANCELLATION OF OVER-THE-AIR SIGNALS

Abstract

First, we build and demonstrate a scalable cancellation system, which is capable of over-the-air multipath cancellation in radio-frequency communications. The analog system uses fiber-optical signal processing instead of traditional radio frequency approaches to achieve wide instantaneous bandwidth and high precision. Channel matching is performed entirely in the optical domain with variable optical attenuators and tunable optical delays. A singlemode to multimode combiner makes this system scalable. Overall, the system achieved 34 dB of narrowband cancellation and > 29 dB of cancellation across 20 MHz of instantaneous bandwidth. Multipath cancellation contributed more than 10 dB of additional cancellation. Second, we use the optical cancellation system to remove self-interference packets in OFDM packet transmission at center frequencies of 2:208 GHz and 2:46 GHz. All signals are generated, transmitted and received using a software defined radio. We report clear trends of improved bit error rate for the signal of interest and worsened bit error rate for the self-interference signal, with up to 5 orders of magnitude difference in BER at 2:208 GHz and up to 3 orders of magnitude difference in BER at 2:46 GHz. This corresponds to a maximum of 15dB improvement in power penalty with cancellation.