Chirp Characterization of External Modulators With Finite Extinction Ratio Using Linear Optical Sampling

We demonstrate a network monitoring technique for the frequency chirping of external modulators based on linear optical sampling. We present ??-parameter waveforms of digital data modulation from simultaneously measured amplitude and phase. Digital data modulation was compared to sinusoidal modulation to demonstrate the measurement capabilities. The high sensitivity of our technique was used to resolve the detailed impact of a 23-dB extinction ratio on the chirp of a Mach-Zehnder modulator. Unlike some previous methods, a monochromator or optical fiber with known dispersion are not required.