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This paper presents a new approach to the optical generation of millimeter-wave signals using a dual-mode multisection distributed feedback semiconductor laser. This simple device is capable of generating high power signals between 40 and 60 GHz with extremely high spectral purity and stability. The two optical modes produced by this laser are heterodyned on an ultrafast photodiode to give a beat signal at the mode difference frequency. The phase noise of the beat signal is greatly reduced by phase-locking the modes using an electrical drive signal applied to the laser at a subharmonic of the beat frequency. Millimeter-wave signals are obtained with a linewidth of less than 10 Hz, a phase noise of less than -85 dBc/Hz at 100 kHz offset, and a locking range of about 500 MHz. Millimeter-wave fiber-radio systems are seen as a major application area for these new compact optical sources.

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Abstract-Optically-powered radio over fiber remote units have been designed and constructed for distributed antenna system applications using separate fibers for power and signal transmission.The feasibility of this approach has been investigated through a series of transmission measurements, based on the IEEE 802.11g wireless local area networking standard at a frequency of 2.5 GHz using 64QAM OFDM modulation at 54 Mb/s. These measurements show that high quality multi-level signal transmission is possible with modest levels of optical power at the central unit. For example, an EVM of around 3 % has been achieved for an RF output power of 0 dBm using a central unit optical power of 250 mW over a link length of 300 m.Index Terms-Distributed antenna systems, power over fiber, radio over fiber, wireless local area networks.

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The diffusion of Be from buried Be-doped layers in GaInAs has been studied for temperatures between 600 and 700 °C. An interstitial-substitutional model is proposed for the diffusion mechanism, which is dependent on growth conditions and consistent with the data presented. Under growth conditions where Be transport is minimized GaInAs junction field-effect transistors have been produced with transconductances in excess of 200 mS mm−1 for a 1-μm gate length.