Signal optimization in glass-fiber self-mixing intra-arterial laser Doppler velocimetry

F.F.M. de Mul, M. van Herwijnen, P. Moes, J. Greve

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    Recently a blood velocimeter was developed, based on the principle of self-mixing in a semiconductor laser. This means that the intensity of the light is modulated by feedback from moving scattering particles, which contains the Doppler shift frequency. Upon feedback the characteristics of the laser diode will change. The threshold current will decrease and an instable region may become present just above the new threshold. It turns out that the amplitude of the Doppler signal is related to the difference in intensity between the situations with and without feedback. This amplitude is highest, but also most unstable, just above feedback. The suppression of reflection from the glass fiber facets is of paramount importance. Using an optical stabilization of the feedback, we are able to optimize the performance of the laser-fiber system and the Doppler modulation depth, and to clarify the behavior with a suitable physical model. The velocimeter has been used in vivo with the glass fiber inserted in normal catheters, but in upstream and in downstream situations. For the latter, the fiber facet in the liquid has been provided with a special side-reflecting device.
    Original languageEnglish
    Title of host publicationOptical Diagnostics of Living Cells and Biofluids
    EditorsDaniel L. Farkas, Robert C. Leif, Alexander V. Priezzhev, Toshimitsu Asakura, Bruce J. Tromberg
    Place of PublicationSan Jose, CA, USA
    Number of pages10
    ISBN (Print)0-8194-2052-2
    Publication statusPublished - 1 Jun 1996
    EventSPIE Photonics West 1996 - San Jose, United States
    Duration: 27 Jan 19962 Feb 1996


    ConferenceSPIE Photonics West 1996
    Country/TerritoryUnited States
    CitySan Jose


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