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Proceedings Paper

SNR of swept SLEDs and swept lasers for OCT (Conference Presentation)
Author(s): Bart C. Johnson; Walid Atia; Dale Flanders; Mark Kuznetsov; Brian Goldberg; Nate Kemp; Peter Whitney

Paper Abstract

A back-to-back comparison of a tunable narrow-band SLED (TSLED) and a swept laser are made for OCT applications. Both are 1310 nm sources sweeping at 50 kHz over a 100 nm tuning range and have similar coherence lengths. The TSLED consists of a seed SOA and two amplification SOAs. The ASE is filtered twice by a tunable MEMS Fabry Perot in a polarization multiplexed double-pass arrangement on either side of the middle SOA. This allows very long coherence lengths to be achieved. A fundamental issue with a SLED is that the RIN is proportional to 1/Linewidth, meaning that the longer the coherence length, the higher the RIN. High RIN also leads to increased clock jitter. Most swept source SNR calculations assume that the noise is independent of the amplitude of the signal light: The higher the signal, the higher the SNR. We show that in the case of the TSLED, that the high signal RIN and clock jitter give rise to additional noises that scale with signal power. This leads to an SNR limit in the case of the TSLED: The higher the signal, the higher the noise, so the SNR reaches a limit. While the TSLED has respectable sensitivity, the SNR limit causes noise streaks in an image where the A-line has a high reflectivity point. The laser, which is shot noise limited, does not exhibit this effect. This is illustrated with SNR data and side-by-side images taken with the two sources.

Paper Details

Date Published: 26 April 2016
PDF: 1 pages
Proc. SPIE 9697, Optical Coherence Tomography and Coherence Domain Optical Methods in Biomedicine XX, 96970R (26 April 2016); doi: 10.1117/12.2214468
Show Author Affiliations
Bart C. Johnson, AXSUN Technologies Inc. (United States)
Walid Atia, AXSUN Technologies Inc. (United States)
Dale Flanders, AXSUN Technologies Inc. (United States)
Mark Kuznetsov, AXSUN Technologies Inc. (United States)
Brian Goldberg, AXSUN Technologies Inc. (United States)
Nate Kemp, AXSUN Technologies Inc. (United States)
Peter Whitney, AXSUN Technologies Inc. (United States)


Published in SPIE Proceedings Vol. 9697:
Optical Coherence Tomography and Coherence Domain Optical Methods in Biomedicine XX
Joseph A. Izatt; James G. Fujimoto; Valery V. Tuchin, Editor(s)

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