Output Signal Characteristics of Optical Fiber Feed Direct Digital RF Transmitter Using SFP+ Module

1-bit band-pass delta-sigma transmitter can generate RF signal from 1-bit data stream which can be fed by optical fiber link designed for Internet usage. It has been reported that the RF signal in the first Nyquist zone can be transmitted from the 1-bit transmitter using fiber link with SFP+ E/O and O/E modules. In this case, the RF frequency which derives from the transmitter is below the half of sampling clock frequency. In order to enhance the transmitted RF frequency, direct digital RF transmitter was proposed in which the image signal component in higher-order Nyquist zone can be extracted from the 1-bit data stream. In this paper, the transmission of image signal of 1-bit delta-sigma transmitter with optical fiber link is discussed. A comparison of image signals characteristics between single-mode 1310 nm fiber link with clock and data recovery and multi-mode 850 nm link without clock and data recovery is carried out. The direct digital RF transmitter with 1310 nm optical fiber feed shows superior performance than that with 850 nm fiber feed.