Large optical power margin of signal light in OFDR-OCT by using semiconductor optical amplifier

Kota Asaka

doi:10.1117/12.765038

18 February 2008 Large optical power margin of signal light in OFDR-OCT by using semiconductor optical amplifier

Kota Asaka

Proceedings Volume 6847, Coherence Domain Optical Methods and Optical Coherence Tomography in Biomedicine XII; 684711 (2008) https://doi.org/10.1117/12.765038
Event: SPIE BiOS, 2008, San Jose, California, United States

Abstract

We demonstrate a sensitivity improvement in an optical frequency domain reflectometry-optical coherence tomography (OFDR-OCT) system with a discretely swept light source by incorporating a semiconductor optical amplifier (SOA) in a sample arm. With the system, we achieve a high sensitivity of -134.4 dB when we measure the reflective mirror with an A-line rate of 0.25 kHz. This improves the sensitivity (-125.2 dB) by 9.2 dB compared with a system without the SOA. The OCT system without the SOA shows a signal-to-noise ratio (SNR) of 56 dB when the signal light power is attenuated by about 66 dB, and the SNRs of less than 56 dB are obtained at higher attenuation levels. However, an SOA-incorporated OCT system provides the SNR of 56 dB at the much higher attenuation level of 86 dB. This means that using the SOA offers the large signal light power margin of 20 dB needed to obtain SNR of 56 dB. It is shown that the power margin is qualitatively dependent on the optical gain of the SOA. From an experimental analysis of the noises in the SOA-incorporated system, we found that the sensitivity enhancement is mainly limited by the beat noise between the reference light and the amplified spontaneous emission (ASE) of the SOA. We obtained images that show clear cluster structures of enamel crystals near the dentin-enamel junction of an extracted human tooth with our SOA-incorporated discretely swept OFDR-OCT imaging, revealing the potential to achieve a high-speed OCT system with high sensitivity.

Citation Download Citation

Kota Asaka "Large optical power margin of signal light in OFDR-OCT by using semiconductor optical amplifier", Proc. SPIE 6847, Coherence Domain Optical Methods and Optical Coherence Tomography in Biomedicine XII, 684711 (18 February 2008); https://doi.org/10.1117/12.765038

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KEYWORDS

Signal to noise ratio

Optical coherence tomography

Semiconductor optical amplifiers

Signal attenuation

Coherence (optics)

Imaging systems

Biomedical optics

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