Filter-assisted direct detection-based field recovery scheme for complex-valued double-sideband signals

Abstract

Double-sideband self-coherent detection (DSB-SCD) can achieve optical field recovery of complex-valued double-sideband (CV-DSB) signals without a local oscillator laser. To date, various proposed DSB-SCD schemes require a high carrier-to-signal power ratio (CSPR) to mitigate the inherent signal-signal beat interference (SSBI) induced by direct detection. Aiming at relaxing the high CSPR requirement for the DSB-SCD, filter-assisted direct detection (FADD) is proposed to retrieve the CV-DSB signals. In this paper, we clarify the concept of the FADD, which uses optical filters in the receiver to achieve optical field recovery of CV-DSB signals via direct detection. The CV-DSB signals can be retrieved at low CSPR with the aid of optical filters. We also propose a novel FADD receiver that uses an optical bandstop filter (OBSF) to obtain CV-DSB signals from self-coherent signals, called OBSF-DD with 90° hybrid. Considering the high complexity of the OBSF-DD with 90° hybrid, a simplified OBSF-DD receiver with 2 × 2 coupler is put forward as well, which uses a 2 × 2 coupler instead of optical hybrid, and three single-ended photodiodes are required to achieve signal reception. By using cost-effective FADD receiver, the proposed FADD scheme provides an effective approach for low CSPR field recovery.