Dynamic Linewidth Measurement Method via an Optical Quadrature Front End

This letter describes a dynamic linewidth characterization method using an optical quadrature front end. The phase noise of the laser is recorded using a real-time oscilloscope in the time domain and the linewidth of the laser can be estimated statistically offline. The major advantage of this technique compared with conventional linewidth measurements in the frequency domain, is that this method enables the dynamic phase noise characterization which is increasingly important for fast wavelength tunable and switched networks employing advanced modulation formats. The dynamic linewidth of an sampled grating distributed Bragg reflector (SG-DBR) laser is characterized by using this method.