Coherence-free photonic notch filter

A new coherence-free photonic notch filter structure is presented. It is based on a Sagnac fibre loop interferometer containing an optical intensity modulator. A notch filter response is obtained by modulating the clockwise and counterclockwise propagating optical waves inside the Sagnac loop at different times. Results demonstrate a robust notch filter operation with a narrow-linewidth laser source, and elimination of phase-induced intensity noise limitations.