Transmission of wideband analogue signals has long presentednsevere design problems concerning provision of a DC-coupled response.nThe paper presents details of a novel split-spectrum transmission methodnwhich achieves optimum spectral performance by combining separate high-nand low-frequency routes, each employing its own modulation technique.nThe resulting DC-coupled analogue system displays an upper frequencynlimit of 400 MHz with an extremely low long-term DC offset of betternthan 50 ΜV over a 1 km length of optical fibre. Extension of thenupper frequency limit is possible simply by specifying improvednhigh-frequency components and is constrained neither by thenlow-frequency elements nor the spectral-splitting approach adopted
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