Optimized Silicon QPSK Modulator With 64-Gb/s Modulation Speed

We demonstrate a compact silicon quadrature phase-shift keying (QPSK) modulator consisting of two nested Mach–Zehnder interferometers with a size of 4.5-mm². TheVΠ · Lof the modulator is 1.4V · cmwith an insertion loss of 8 dB. In addition, 64-Gb/s QPSK modulation is achieved with an error vector magnitude (EVM) of 24.4% and bit error rate (BER) of 2.1×10⁻⁵$at the received optical power of$-$10 dBm after the device and an EVM of 31.7% and BER of 8.4$×10⁻⁴at the received optical power of 0 dBm after 10-km single-mode fiber transmission. The estimated power consumption is 7.1 pJ/bit for the 64-Gb/s QPSK modulation.