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-
${\rm mm}^{2}$
. The
${\rm V}_{\Pi} \cdot {\rm L}$
of the modulator is 1.4
${\rm V} \cdot {\rm cm}$
with 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
$\times$

$10^{-5}$
at the received optical power of
$-$
10 dBm after the device and an EVM of 31.7% and BER of 8.4
$\times$

$10^{-4}$
at 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.