THE EFFECT OF MODULATOR NONLINEARITY ON MEASUREMENTS OF CHIRP IN ELECTROABSORPTION MODULATORS

Traditional techniques for measuring the chirp in external modulators assume that the optical intensity output of the modulator is a faithfu l representation of the applied voltage. For electroabsorption modulat ors, which can have highly non-linear transmission- vs voltage charact eristics, this is a poor approximation, especially when they are opera ted at high modulation indices. We demonstrate a new technique that ma kes use of the actual measured T(V) for the device under test, and sho w that this new technique permits measurement of chirp in modulators g enerating either NRZ signals or soliton pulses. We apply this techniqu e to both bulk and MQW electroabsorption modulators, and show that tra ditional measurements significantly underestimate the alpha values of these devices.