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Proceedings Paper

Dispersive Fourier transform using few-mode fibers for real-time and high-speed spectroscopy
Author(s): Yi Qiu; Chi Zhang; Kenneth K. Y. Wong; Kevin K. Tsia
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Paper Abstract

Dispersive Fourier Transform (DFT) is a powerful technique for real-time and high-speed spectroscopy. In DFT, the spectral information of an optical pulse is mapped into time using group velocity dispersion (GVD) in the dispersive fibers with an ultrafast real-time spectral acquisition rate (>10 MHz). Typically, multi-mode fiber (MMF) is not recommended for performing DFT because the modal dispersion, which occurs simultaneously with GVD, introduces the ambiguity in the wavelength-to-time mapping during DFT. Nevertheless, we here demonstrate that a clear wavelength-to-time mapping in DFT can be achieved by using the few-mode fibers (FMFs) which, instead of having hundreds of propagation modes, support only a few modes. FMF-based DFT becomes appealing when it operates at the shorter wavelengths e.g. 1-μm range, a favorable spectral window for biomedical diagnostics, where low-cost single mode fibers (SMFs) and high-performance dispersion-engineered fibers are not readily available for DFT. By employing the telecommunication SMFs (e.g. SMF28), which are in effect FMFs in the 1-μm range as their cut-off wavelength is ~1260 nm, we observe that a 3nm wide spectrum can be clearly mapped into time with a GVD as high as -72ps/nm and a loss of 5 dB/km at a spectral acquisition rate of 20 MHz. Moreover, its larger core size than the high-cost 1-μm SMFs renders FMFs to exhibit less nonlinearity, especially high-power amplification is implemented during DFT to enhance the detection sensitivity without compromising the speed. Hence, FMF-based DFT represents a cost-effective approach to realize high-speed DFT-based spectroscopy particularly in the biomedical diagnostics spectral window.

Paper Details

Date Published: 30 January 2012
PDF: 6 pages
Proc. SPIE 8218, Optical Fibers and Sensors for Medical Diagnostics and Treatment Applications XII, 82180P (30 January 2012); doi: 10.1117/12.907785
Show Author Affiliations
Yi Qiu, The Univ. of Hong Kong (Hong Kong, China)
Chi Zhang, The Univ. of Hong Kong (Hong Kong, China)
Kenneth K. Y. Wong, The Univ. of Hong Kong (Hong Kong, China)
Kevin K. Tsia, The Univ. of Hong Kong (Hong Kong, China)

Published in SPIE Proceedings Vol. 8218:
Optical Fibers and Sensors for Medical Diagnostics and Treatment Applications XII
Israel Gannot, Editor(s)

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