Johansson, Leif Albin; (2002) Broadband millimetre-wave radio over fibre systems. Doctoral thesis (Ph.D.), University College London (United Kingdom).

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Abstract

This thesis concerns the generation and transmission of millimetre wave modulated optical signals for broadband radio over fibre applications. The millimetre wave modulated optical source used for this application should be able to produce single sideband modulation with high modulation depth and high power to overcome the fibre chromatic dispersion and attenuation for transmission distances longer than a few kilometres. In addition to these demands, the source should have long-term stability and the potential for low cost. Previous sources do not satisfy these demands. In this work, a novel millimetre wave modulated optical source is demonstrated, the first millimetre wave modulated optical injection phase-lock loop. It is shown how stable and efficient generation of single sideband modulated optical signals can be accomplished using standard components and how this source can be used for transmission of broadband millimetre wave modulated optical signals over up to 65 km of unamplified standard singlemode fibre. Experimental results are presented on the generation of a single sideband modulated optical signal with high spectral purity- -93 dBc/Hz at 10 kHz offset and -107 dBc/Hz at 2 MHz offset, wide locking range- more than 30 GHz and wide tuneability- potentially from 4 GHz to more than 60 GHz. This source has been used for optical transmission of a 140 Mbit/s amplitude shift keyed modulated 36 GHz carrier over 25 km of unamplified standard single mode fibre and over 65 km using optical amplification. The source has also been used to demonstrate optical transmission of a 68 Mbit/s DPSK modulated 36 GHz carrier over 65 km unamplified standard single mode fibre, using a modulated reference. This is the longest demonstrated unamplified transmission of broadband (>10 Mb/s) millimetre wave radio over fibre transmission and the widest bandwidth reference modulation applied to either an OPLL or an OIL based heterodyne system.

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