ABSTRACT
Electroabsorption modulators (EAM) are suitable for use in compact fiber optical transmitters for high speed and efficiency. This chapter introduces the fundamental operation of traveling-wave (TW) optical modulators suitable for binary intensity modulation in high-speed fiber optical communications. It discusses the microwave properties as well as different implementations of transmission lines (TML). The optical absorption process in EAMs is either based on the bulk Franz-Keldysh effect or the quantum-confined Stark-effect. For optimum performance of a TW device the optical and the electrical waves should propagate at the same velocity. The TML attenuation is usually the dominating bandwidth limitation for TW-EAMs. Due to the low conductivity of p-InP the voltage over the intrinsic layer is lower than the voltage on the modulator electrode. This can cause a significant penalty on the transfer function if the intrinsic layer is chosen to be too thin.
