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A directly modulated and coherently injection-locked WRC-FPLD transmitter is preliminarily employed to perform the 16-QAM-OFDM data transmission by using an OFDM subcarrier amplitude pre-leveling technique. The maximum transmission bit-rate of 20-Gbit/s is reported by fusing the OFDM subcarrier pre-leveling with the coherent injection-locking techniques in such a directly modulated WRC-FPLD. Without pre-leveling the OFDM subcarrier, the coherently injection-locked L-band WRC-FPLD suppresses its mode-partition noise to improve the EVM of the 16-QAM-OFDM data only from 13.52% to 10.2%. The OFDM subcarrier pre-leveling effectively compensate the finite bandwidth and unflattened modulating response of the injection-locked WRC-FPLD to improve the transmission EVM and SNR performances. The received constellation plot reveals that the EVM and SNR of the back-to-back transmitted 16-QAM-OFDM data are significantly improved to 5.58% and 17 dB, respectively. With the use of both injection-locking and pre-leveling techniques, the directly 16-QAM-OFDM modulated WRC-FPLD transmitter can reach the FEC limited BER of 3.8 × 10-3 at a receiving power sensitivity of -10 dBm. The OFDM subcarrier pre-leveling technique helps the WRC-FPLD to reduce the overall BER of 16-QAM-OFDM data by one order of magnitude, providing a minimum BER of 4.5 × 10-5 at a receiving power of -2 dBm.
Date of Publication: April1, 2013