TABLE OF CONTENTS Microwave signals are traditionally transmitted via coaxial cables and waveguides, which are very lossy and suffer from electromagnetic interference. Fibre-optic links offer a good alternative because of low-loss, high bandwidth, and immunity to electromagnetic interference. In recent years, much effort has been devoted to optical generation of millimetre-wave (mm-wave) signals for applications such as fibre-fed wireless communication systems and phased array antennas [ [1], [2]]. In novel radio-over-fibre systems, integration between optical and microwave devices may be required [ [3] [4] [5]]. Therefore, equivalent circuit models of optical devices are handy simulator tools that can be combined with existing circuit models of microwave devices for design and optimisation in such systems.
Microwave circuit techniques are well-established in the microwave research community and equivalent circuit models of microwave devices have been extensively used for design and modelling purposes for many years now [ [6], [7]]. However, well-accepted circuit models of laser diodes are still rare compared to that of microwave devices. In this chapter, an introduction of a lumped-element circuit model, based on the laser rate equations, is first presented. Lumped-element circuit models of laser diodes have been used for many different applications in recent years [ [8] [9] [10] [11] [12] [13] [14] [15] [16] [17] [18] [19] [20] [21]]. These equivalent circuit models based on lumped-elements are useful in the fast emerging research area of microwave photonics because of the insight they provide and for their simplicity [ [22],
