Abstract
We present theoretical and experimental results which demonstrate the superior sensitivity of swept source (SS) and Fourier domain (FD) optical coherence tomography (OCT) techniques over the conventional time domain (TD) approach. We show that SS- and FD-OCT have equivalent expressions for system signal-to-noise ratio which result in a typical sensitivity advantage of 20-30dB over TD-OCT. Experimental verification is provided using two novel spectral discrimination (SD) OCT systems: a differential fiber-based 800nm FD-OCT system which employs deep-well photodiode arrays, and a differential 1300nm SS-OCT system based on a swept laser with an 87nm tuning range.
Highlights
In the decade since its introduction, optical coherence tomography (OCT) has proven to be an important modality for micrometer-scale imaging [1]
This is significantly higher than the time domain (TD)-OCT SNR of 107 dB predicted from Eq (9), and is consistent with the 126 dB of SNR predicted by Eq (10)
This fall-off phenomenon previously has been observed in swept source (SS)-OCT [7] and in Fourier domain (FD)-OCT [4], and may be addressed by numerically resampling the data to correct for these nonlinearities [16]
Summary
In the decade since its introduction, optical coherence tomography (OCT) has proven to be an important modality for micrometer-scale imaging [1]. Virtually all systems built for clinical and biological use have employed a variable group delay reference arm to coherently gate backscattered light from various depths in a sample. While successful, this time domain (TD) approach is hampered by the relatively complicated optical and mechanical designs needed to scan ~10ps delays at kilohertz rates in order to achieve real-time imaging. The second method, sweptsource OCT (SS-OCT) [2,6,7,8,9], time-encodes wavenumber by rapidly tuning a narrowband source through a broad optical bandwidth. We accomplish this by deriving and experimentally validating an SNR expression for SS-OCT and by showing that SS-OCT and FD-OCT have equivalent SNR expressions
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