300 Mbps photonic QPSK modulator for space applications

Abstract

This paper addresses the evolution of the photonic QPSK modulator setup previously reported. This second generation setup used two laser sources and the bias tee was replaced by a power combiner. As a result, the second setup enables one to reach higher data rates with better stability and modulated signal quality. The improved setup initially achieved a data rate of 50 Mbps in a QPSK scheme with an EVM of 8%. Using a root-raised-cosine filter, it was possible to reduce the EVM to 4.5%. After the EVM analysis, the modulated signal was demodulated through an actual satellite receiver. Using the demodulator, it was possible to measure the BER and verify if the incoming signal was modulated in the correct order. The QPSK modulator achieved finally a bit rate of 300 Mbps. The degradation analysis of the modulator with QPSK modulation and bit rate of 100 Mbps was 0.06 dB. In this case the values of Eb/N0 and BER were 11.36 dB and 10∼7. The obtained results are a consequence of the photonic technology bandwidth and the improvement made in the input and bias circuit.