High dynamic range fiber optic links using semiconductor electro absorption modulators

In this paper, we report that large SFDR are obtained in Franz-Keldysh effect (FKE) waveguide modulators by adjusting the DC bias. This is achieved by low-biasing at the null in the third derivative of the transfer curve. Only 3 dB of excess loss is required to gain 22 dB in the dynamic range which is a big improvement over the Mach-Zehnder low-biasing result. This improvement is due to the exponential-like transfer function of the FKE modulator, for which the third-order derivative null is attained at a bias with higher slope efficiency than for the cosine-squared transfer function of the Mach-Zehnder.