Accurate determination of transient chirpparameter in high speed digital lightwave transmitters

The authors report a simple yet accurate method for determining the transient α-parameter based on the output pulse and time resolved frequency chirp data. This new method is applied to 10 and 20 Gbit/s Ti:LiNbO3 modulator-based transmitters driven by NRZ data with pseudo-random bit sequence. The calculated time resolved frequency chirp using this newly determined α-parameter closely matched to the measured data. It is also shown that the conventional α-parameter values determined using the electrical signal ratio applied to the modulator section grossly under-estimates the actual values.