10 Gbit/s optical receiver of lossless tuned pin-HEMT with h - Electronics Letters

transmitting the packets through a laser, optical fibre, photodetector and demodulator. The BER of the DPA-recovered channel is shown in Fig. 3 . The ideal curve has been measured by connecting the clock directly from the transmitter to the receiver, while the DPA BER has been measured with I , 2 and 4bit preamble lengths. Longer preambles have not been considered because of the increased complexity of the required logic and the small improvement over the 4 bit preamble (see Fig. 2). Our theoretical analysis and experimental measurements suggest the following conclusions: (i) the prototype performance agrees very well with the calculation (compare Fig. 3 with Fig. 2); (ii) the 4 bit DPA has only 1 dB penalty as against the ideal receiver, and the 2bit DPA has only 0.XdB additional penalty; (iii) the DPA performs a clock acquisition from scratch in 5011s (four preamble bits) or 2511s (two preamble bits), outperforming all other clock recovery devices. The better performance of the 4bit DPA over the 2 bit is due to the fact that it averages over four preamble bits instead of two, therefore reducing the effect of noise and jitter. The bit rate of our current prototype is limited by the availability of components (high-resolution delay lines and fast programmable logic devices) and metastability. A much faster fully-custom designed single-chip CMOS implementation of the DPA using 64 preamble bits for 2.5Gbith bit streams is currently being developed.