TABLE OF CONTENTS Recently, there have been proposals for using semiconductor lasers as sources of millimetre-wave signal for mobile broadband communication systems [ [2], [3], [71]]. Increasing interest in millimetre-wave fibre-radio systems has also lead to the investigation of optical signal-processing techniques for microwave and millimetre-wave signal generation by Lowery and Gurney [ [72]]. In microwave and millimetre-wave applications, the laser diode should be matched to the signal generator to minimise reflections due to impedance mismatch [ [73]]. In addition, high levels of RF power are required to overcome the losses associated with the electrical cable, bias tee, and laser mount.
Matching networks are often preferred to the conventional method of connecting a chip resistor (43-48 ?) in series with the laser diode [ [67]]. The reason is matching networks provide better power transfer between the signal generator and laser diode. Broadband operation, however, becomes more difficult to achieve. There have been numerous reports of matching techniques for laser diode transmitters. Narrowband techniques (typically 10-15% of signal bandwidth) include quarter-wave transformers (QWT) [ [74]] and stub tuning [ [64]]. Broadband techniques (100% or more of signal bandwidth) include the pseudo-bandpass LC ladder network [ [75]] and the resonant circuit step transformer [ [69]]. In practice, the matching is degraded due to the parasitics, and there are also constraints imposed by the matching elements themselves, e.g. realisation of transmission-line segments in microstrip are limited to impedances between 10 and 120
