Parallel Fiber Loop Interferometer-Based Self-Interference Cancellation for IBFD Distributed Antenna Systems

Distributed Antenna Systems (DAS) are gaining popularity as a solution for providing cellular coverage and capacity in areas with weak signal strength or high user density. In this paper, we propose and validate a photonics-aided self-interference (SI) cancellation system based on a parallel fiber interferometer and an FBG sensor. To demonstrate an in-band full-duplex communication system based on DAS, we use a dual-polarization Mach-Zehnder modulator (D-Pol MZM) as an SI canceller, coupled in a clockwise direction. Frequency down-conversion after SI cancellation is achieved using an MZM modulated with a local oscillator. An FBG sensor is used to remove the optical carrier after the loop for dispersion compensation. Over a frequency range of 20 GHz to 40 GHz, the system achieves an average SI cancellation depth of 46.07 dB, as shown by the validation results. The system also shows gains of 31.25 dB, 33.28 dB, and 31.96 dB for down-converted signals at 8 GHz, 10 GHz, and 12 GHz, respectively. For big places like stadiums and venues that need to handle many wireless users, the suggested way can be a good option for using IBFD based DAS to communicate.