title: Photonic downconversion based on optical carrier bidirectional reusing in a phase modulator.
abstract: We propose a novel photonic downconversion method based on optical carrier reusing. In the proposed system, the phase modulator (PM) is placed between two narrowband fiber Bragg gratings (FBGs), which are designed to reflect the optical carrier and transmit the optical sidebands. The optical carrier is modulated in the PM in two directions and is not injected into the photodetector (PD). Thus, the utilization ratio of the optical carrier is enhanced and the power saturation in the PD is avoided. Consequently, the system gain can be improved. In addition, a 2×2 optical coupler is cooperated with a balanced PD behind these two FBGs. Resulting from the subtle design of the phase difference, gain is furthermore doubled and intensity noise can be reduced simultaneously. In the experiments, 29 dB gain improvement is measured compared with the traditional dual-series intensity modulators method. The noise floor is reduced by 12.1 dB.
authors.forename: Tianwei
authors.initials: T
authors.lastname: Jiang
authors.forename: Song
authors.initials: S
authors.lastname: Yu
authors.forename: Qian
authors.initials: Q
authors.lastname: Xie
authors.forename: Jian
authors.initials: J
authors.lastname: Li
authors.forename: Wanyi
authors.initials: W
authors.lastname: Gu