An optical coherence tomography (OCT) system for imaging a sample, the OCT system comprising: an optical circuit comprising an interferometer , the optical circuit being configured to probe the sample and generate an analog OCT signal representative of the sample; and a digitization circuit configured to receive, down convert and digitize the analog OCT signal, thereby outputting a digitized down converted signal, wherein the digitalization circuit comprises : an analog to digital converter configured to digitize the analog OCT signal, thereby obtaining a digital OCT signal, and a frequency down converter located downstream of the analog-to-digital converter and configured to down convert the digital OCT signal into the digitized down converted signal, the .frequency down converter comprising: a local oscillator configured for generating a local oscillator signal having a spectrum centered around a local frequency, and a mixer (44; 64,66) operatively connected to the local oscillator and configured to receive the digital OCT signal and mix the digital OCT signal with the local oscillator signal to obtain the digitized down converted signal, characterized in that the OCT system further comprises a servo-loop configured to maintain the local oscillator frequency close to a frequency of the digital OCT signal. an optical circuit comprising an interferometer , the optical circuit being configured to probe the sample and generate an analog OCT signal representative of the sample; and a digitization circuit configured to receive, down convert and digitize the analog OCT signal, thereby outputting a digitized down converted signal, wherein the digitalization circuit comprises : an analog to digital converter configured to digitize the analog OCT signal, thereby obtaining a digital OCT signal, and a frequency down converter located downstream of the analog-to-digital converter and configured to down convert the digital OCT signal into the digitized down converted signal, the .frequency down converter comprising: a local oscillator configured for generating a local oscillator signal having a spectrum centered around a local frequency, and a mixer (44; 64,66) operatively connected to the local oscillator and configured to receive the digital OCT signal and mix the digital OCT signal with the local oscillator signal to obtain the digitized down converted signal, an analog to digital converter configured to digitize the analog OCT signal, thereby obtaining a digital OCT signal, and a frequency down converter located downstream of the analog-to-digital converter and configured to down convert the digital OCT signal into the digitized down converted signal, the .frequency down converter comprising: a local oscillator configured for generating a local oscillator signal having a spectrum centered around a local frequency, and a mixer (44; 64,66) operatively connected to the local oscillator and configured to receive the digital OCT signal and mix the digital OCT signal with the local oscillator signal to obtain the digitized down converted signal, a local oscillator configured for generating a local oscillator signal having a spectrum centered around a local frequency, and a mixer (44; 64,66) operatively connected to the local oscillator and configured to receive the digital OCT signal and mix the digital OCT signal with the local oscillator signal to obtain the digitized down converted signal, characterized in that the OCT system further comprises a servo-loop configured to maintain the local oscillator frequency close to a frequency of the digital OCT signal. <EOS>