Figure 4

(a) Active characterization setup including a 980 nm laser pump source together with a polarization controller to ensure the fundamental TE mode is coupled into the Al₂O₃:Er³⁺ DBR laser, an OSA to monitor the DBR laser output, a temperature control feedback loop to modify and monitor the temperature of the system, and a TIA to amplify the electrical signal that is then monitored by the oscilloscope. (b) Optical spectrum of the DBR laser recorded by the OSA, showing >30 dB SMSR. (c) The subtraction between the original binary data for signal generator and the received binary data from Ge photodetector gives all zero, showing data transmission without error bit.