Photonics-Based Scheme to Generate Broadband Signal with Controllable Negative Signal-to-Noise Ratio

A photonics-based scheme for generating broadband signals with controllable negative signal-to-noise ratio (SNR) is proposed and experimentally verified. By introducing an amplified spontaneous emission (ASE) light source and a programmable optical filter (POF), wideband noise signals with tunable power and shape are achieved. The optically carried RF signal and the noise are coupled in the optical domain. After photodetection, the wideband signal with negative SNR will be generated. A feedback mechanism based on a differential evolution (DE) algorithm is introduced to control the POF, enabling the dynamic adjustment of the signal's SNR. A concept of experiment is taken. The radio frequency (RF) signals with SNR tuning from -3 to -7 dB over a 1-GHz bandwidth are experimentally generated. The SNR error is less than <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\pm \mathbf{0.1}\ \mathbf{dB}$</tex>. The experimental performance of the proposed system for the communication application is verified.