Microwave Signal Generation Using Self-Heterodyning of a Fast Wavelength Switching SG-DBR Laser
Available at: https://digitalcommons.calpoly.edu/theses/19
Date of Award
MS in Electrical Engineering
Microwave signal generation is demonstrated using a single-chip fast wavelength-tunable SG-DBR laser. Microwave signals are established by a delayed self-heterodyne technique. The optical frequency of the laser is square-wave modulated between two closely spaced wavelengths. These two wavelengths are made time coincident using a fiber based Mach-Zehnder interferometer. From the interferometer, the difference frequency is detected and amplified. The optical difference frequency takes on the form of a microwave signal that can be seen on an electrical spectrum analyzer. The hardware structure of the high-speed wavelength switching SG-DBR package is shown. The wavelength switching architecture and temperature robustness of the laser will also be presented.
Microwave signals up to 17 GHz have been generated by frequency modulating the phase section of the laser. Measured from the microwave signal spectral width, laser linewidth values as narrow as 10 MHz have been achieved for low back mirror current inputs. Linewidth results with respect to device DC bias conditions are also presented. Time resolved frequency step measurements have shown inherent thermal transients of approximately 200 ns upon wavelength switching. From the square wave switching profile, switching times of approximately 24 ns were achieved.