Comparative signal-to-noise analysis of fibre-optic based optical coherence tomography systems

Abstract

Several optical coherence tomography (OCT) systems are proposed using optical-fibre components and based around Fizeau sensing interferometers. The theoretical signal-to-noise ratio (SNR) is calculated for each of the proposed configurations, using a constant set of assumed values for illumination and detection parameters. The SNR values obtained are compared with values calculated for typical existing configurations based around Michelson interferometers. Fizeau-based systems incorporating a secondary processing interferometer offer the advantage over current interferometer configurations of down-lead insensitivity, which prevents signal fading and reduces thermal fringe drift. The most basic form of the Fizeau system makes inefficient use of optical power, and has a low SNR compared with the widely used Michelson configuration. However, the results of the analysis described in this paper show that the SNR for more sophisticated Fizeau configurations, incorporating optical circulators and balanced detection systems, can be as high as the value for the most sensitive existing fibre-based OCT systems. Fizeau configurations therefore offer the combined advantages of optimized SNR and down-lead insensitivity, indicating their suitability for use in relatively poorly controlled environments such as in-vivo measurements.

Optical coherence tomography today: speed, contrast, and multimodality

“…The path length difference in the external interferometer determines the depth in the sample. [88][89][90] Oh et al used a Michelson interferometer as an external interferometer, a Linnik interferometer at the distal end of the optical fiber probe, and a fiber bundle for 2-D image collection. A spatially and temporally incoherent Xenon arc lamp light source was used.…”

Performance analysis of a swept-source optical coherence tomography system with a quadrature interferometer and optical amplification

“…By extending the noise analysis of SS-OCT [18] with mismatched balanced detection [6,22] to our QSS-OCT system with the SOA inserted into on the sample arm, the mathematical expression of the photocurrent variances for each noise components is [17,21]:…”

“…where, B is the detector bandwidth, NEPh is the noise equivalent photocurrent density of detector, P r = P 0 ⋅ k 1 ⋅ k 2 ⋅ R is the optical power reflected from reference arm arriving at the photodiodes, 2 and P incs = P 0 ⋅ (1 − k 1 ) ⋅ k 2 ⋅ X are the coherent and incoherent optical powers reflected from sample arm arriving at the photodiodes [21], P sp0 is the spontaneous emission power of the SOA arriving at the photodiodes when G =1. β is a balanced factor and β = 1 represents a completed balanced system.…”

“…(1) and (2) for a complex discrete Fourier transform (DFT). Then, the maximum-squared signal power in our system with the dual-balanced quadrature detection is given as [5,21]…”

“…(5) and (6) are written under the assumption of no excess losses in the system. The SNR of our QSS-OCT system with the SOA inserted for weak sample signal amplification is described as [5,21]:…”