4 May 1998 Optical replication technique for wideband transient waveform digitization
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In many modern military systems it is necessary to digitize wideband data of bandwidth up to 10 GHz or more at say 8-bit accuracy for subsequent processing by computer. This is currently beyond the capability of any single current electronic A/D converter, and a variety of alternative techniques have been investigated to alleviate this problem. In the laboratory a digital sampling oscilloscope can digitize signals of bandwidth up to at least 50 GHz, but only through the use of a repetitive input waveform. Our technique involves amplitude-modulating a single radar return on to the output of a laser diode, and using of an assembly of single-mode optical fiber delay lines and couplers to replicate this optical waveform in time, effectively converting it into a repetitive (optical) waveform. This repetitive waveform is converted back to the electrical domain through a photodiode, and sampled with a conventional (relatively) low-speed ADC. The latter operates in a Vernier mode, taking successive samples at different elapsed times in the replicated electrical waveforms, so as to build up a complete record of the waveform. The paper discusses the design of the system and various practical issues, and presents preliminary results on its operation.
© (1998) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Alan Johnstone, Alan Johnstone, Meirion F. Lewis, Meirion F. Lewis, Jonathan D. Hares, Jonathan D. Hares, "Optical replication technique for wideband transient waveform digitization", Proc. SPIE 3285, Fabrication, Testing, Reliability, and Applications of Semiconductor Lasers III, (4 May 1998); doi: 10.1117/12.307609; https://doi.org/10.1117/12.307609

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