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Optical Engineering

Using a discrete thermal model to obtain a linear frequency ramping in a frequency-modulated continuous-wave system
Author(s): Daniel Nordin; Kalevi Hyyppae
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Paper Abstract

The lasing wavelength of a single-section distributed feedback (DFB) laser diode can be modulated by modulating the drive current. This makes it possible to utilize the DFB laser diode in a frequency-modulated continuous wave (FMCW) range and velocity measuring system. In FMCW, the frequency of the laser is ramped, and the frequency difference between the reflected wave and a local-oscillator wave is monitored. For maximum performance the frequency ramping should be linear. Due to thermal phenomena, a linear ramping of the current seldom results in a linear ramping of the optical frequency. We have derived a discrete thermal model, using resistors and capacitors, of our laser module. The thermal model was then used as a starting point to model the frequency behavior of the laser and to derive modulation currents that resulted in a linear frequency ramping at some different modulation frequencies.

Paper Details

Date Published: 1 July 2005
PDF: 6 pages
Opt. Eng. 44(7) 074202 doi: 10.1117/1.1949205
Published in: Optical Engineering Volume 44, Issue 7
Show Author Affiliations
Daniel Nordin, Luleå Univ. of Technology (Sweden)
Kalevi Hyyppae, Luleå Univ. of Technology (Sweden)


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