Superlinear growth of Rayleigh scattering-induced intensity noise in single-mode fibers

TL;DR

This paper investigates how Rayleigh scattering-induced intensity noise in single-mode fibers exhibits superlinear growth with fiber length when using narrow linewidth lasers, challenging previous third-order nonlinear scattering models.

Contribution

It demonstrates that the noise behavior with narrow linewidth lasers deviates from the linear scaling, indicating a different underlying scattering mechanism.

Findings

Noise power scales superlinearly with fiber length up to 10 km in certain frequency ranges.

Bandwidth of the noise plateau is approximately 10 kHz.

Results challenge the third-order nonlinear scattering explanation for the noise.

Abstract

Rayleigh scattering generates intensity noise close to an optical carrier that propagates in a single-mode optical fiber. This noise degrades the performance of optoelectronic oscillators and RF-photonic links. When using a broad linewidth laser, we previously found that the intensity noise power scales linearly with optical power and fiber length, which is consistent with guided entropy mode Rayleigh scattering (GEMRS), a third order nonlinear scattering process, in the spontaneous limit. In this work, we show that this behavior changes significantly with the use of a narrow linewidth laser. Using a narrow linewidth laser, we measured the bandwidth of the intensity noise plateau to be 10 kHz. We found that the scattered noise power scales superlinearly with fiber length up to lengths of 10 km in the frequency range of 500 Hz to 10 kHz, while it scales linearly in the frequency range of 10 Hz to 100 Hz. These results suggest that the Rayleigh-scattering-induced intensity noise cannot be explained by third-order nonlinear scattering in the spontaneous limit, as previously hypothesized.