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arXiv · 2507.13128

Phase noise measurement of semiconductor optical amplifiers

Damien Teyssieux·Martin Callejo·Jacques Millo·Enrico Rubiola·Rodolphe Boudot
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Abstract

We introduce a novel measurement method for the phase noise measurement of optical amplifiers, topologically similar to the Heterodyne Mach-Zehnder Interferometer but governed by different principles, and we report on the measurement of a fibered amplifier at 1.55 $μ\mathrm{m}$ wavelength. The amplifier under test (DUT) is inserted in one arm of a symmetrical Mach-Zehnder interferometer, with an AOM in the other arm. We measure the phase noise of the RF beat detected at the Mach-Zehnder output. The phase noise floor of the amplifier decreases proportionally to the reciprocal of the laser power at the amplifier input, down to $-125$ $\mathrm{dBrad^2/Hz}$ at $f=100$ $\mathrm{kHz}$. The DUT flicker noise cannot be measured because it is lower than the background of the setup. This sets an upper bound of the amplifier noise at $-32$ $\mathrm{dBrad^2/Hz}$ at $f=1$ $\mathrm{Hz}$, which corresponds to a frequency stability of $5.2{\times}10^{-17}/τ$ (Allan deviation), where $τ$ is the integration time. Such noise level is lower than that of most Fabry-Perot cavity-stabilized lasers. These results are of interest in a wide range of applications including metrology, instrumentation, optical communications, or fiber links.

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Damien Teyssieux, Martin Callejo, Jacques Millo, Enrico Rubiola, Rodolphe Boudot. 2025-10-02. Phase noise measurement of semiconductor optical amplifiers. https://doi.org/10.1109/jlt.2025.3627489

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