Bright seeded and quasi-continuous two-mode intensity squeezing in commercial fiber

Squeezed states of light enable optical measurements with sensitivity beyond the shot noise limit of detection with classical light. Optical fibers represent a major potential platform for quantum squeezed sensing due to the extremely low loss and perfect single-spatial-mode operation. In this work, we demonstrate two-mode intensity squeezing directly within a commercially available optical fiber, based on a four-wave mixing process. The setup operates in a quasi-continuous-wave mode using 15 ns long pulses and relies on standard laser diode sources, telecommunication electro-optic modulators, and simple photo-detectors. The process is seeded by a coherent signal input, generating bright squeezed output states. Absolute noise reduction by 4 dB below the classical shot-noise limit is detected directly with no post-processing, for output signal and idler pulses of 2.4 × 10⁶ photons in average. The results are applicable to quantum interferometry over fiber using simple, readily available components.