Accurate determination of transient chirp parameter in high speed digital lightwave transmitters

The authors report a simple yet accurate method for determining the transient a-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 the measured data. It is also shown that the conventional a-parameter values determined using the electrical signal ratio applied to the modulator section grossly underestimates the actual values