Related Experiment Video
Updated: Apr 1, 2026
09:38
Characterizing Far-infrared Laser Emissions and the Measurement of Their Frequencies
Published on: December 18, 2015
12.8K
Coherence enhancement of a chirped DFB laser for frequency-modulated continuous-wave reflectometry using a composite
Optics Letters
|October 1, 2015
Summary
We improved chirped distributed feedback (DFB) lasers for frequency-modulated continuous-wave (FMCW) reflectometry by suppressing noise. This enhances coherence, enabling longer-range measurements with higher resolution.
Area of Science:
- Optics and Photonics
- Laser Physics
- Metrology
Background:
- Frequency-modulated continuous-wave (FMCW) reflectometry requires highly linear frequency chirps from lasers.
- Chirped distributed feedback (DFB) lasers are susceptible to sweep nonlinearity and broadband frequency noise, limiting FMCW performance.
Purpose of the Study:
- To demonstrate efficient coherence enhancement of a chirped DFB laser for FMCW reflectometry.
- To suppress sweep nonlinearity and broadband frequency noise during laser chirp.
Main Methods:
- Implementation of a composite feedback loop to control the laser chirp.
- Characterization of residual frequency error and broadband frequency noise suppression.
Main Results:
- Residual frequency error reduced to 89 kHz (from 44 MHz) for a 50 GHz chirp over 100 ms.
- Achieved 2 mm spatial resolution at 50 m and 17.5 cm resolution at 750 m.
- Extended measurement range by approximately 15 times the intrinsic coherence length.
Conclusions:
- The composite feedback loop effectively suppresses noise and nonlinearity in chirped DFB lasers.
- Enhanced laser coherence significantly improves FMCW reflectometry performance, enabling extended range and resolution.
