Impedance matching of laser diodes using packaged microstrip lines: active and passive

Summary form only given. Impedance matching of laser diodes using packaged microstrip structures is discussed for both active and passive matching networks. The first step in accomplishing any reasonable match to driving a laser diode requires a careful measurement of the input impedance of the packaged laser diode. Although the nonlinear behavior of a laser diode presents a frequency dependent impedance and is dependent upon the threshold current, the impedance of the Mitsubishi laser diode used in our case was given as approximately a series resistance of 4 ohms plus an inductance of 3 nanoHenrys for a frequency range of 0.5 GHz to 5 GHz when the laser is modulated above threshold. The task to be accomplished then is to provide a matching circuit to the laser diode providing an efficient throughput of modulator power. An example of a simple single stub matching circuit fabricated on microstrip is shown. The results of both the passive and active matching circuits will be presented