Optoacoustics (OA) is overwhelmingly implemented in the Time Domain (TD) to achieve high signal-to-noise ratios (SNR) by maximizing the excitation light energy transient. Implementations in the Frequency Domain (FD) have been proposed, but suffer from low SNR and have not offered competitive advantages over TD methods. It is therefore commonly believed that TD is the optimal way to perform optoacoustics. Here we introduce an optoacoustic concept based on pulse train illumination and FD multiplexing and theoretically demonstrate the superior merits of the approach compared to the TD. Then, using recent advances in laser diode illumination, we launch Frequency Wavelength Multiplexing Optoacoustic Tomography (FWMOT), at multiple wavelengths, and experimentally showcase how FWMOT optimizes the SNR of spectral measurements over TD methods in phantoms and in vivo. We further find that FWMOT offers the fastest multi-spectral operation ever demonstrated in optoacoustics.
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