Transmission of a 56 Gbit/s PAM4 signal with low-resolution DAC and pre-equalization only over 80 km fiber in C-band IM/DD systems for optical interconnects
Mingzhu Yin, Dongdong Zou, Wei Wang, Fan Li, Zhaohui Li
Abstract
A low-cost intensity modulation and direct detection scheme using a 4-bit digital-to-analog converter for 56 Gbit/s pre-equalized PAM-4 generation at the transmitter and without receiver side post-equalization over 80 km single-mode fiber transmission in a C-band is experimentally demonstrated in this Letter. Pre-equalization includes pre-emphasis for channel response, a modified Gerchberg–Saxton algorithm with five iterations for chromatic dispersion compensation, and a noise shaping technique implemented by a five-tap finite impulse response filter for quantization noise suppression. Enabled by the pre-equalization techniques, the bit error rate of the received signal without post-equalization can reach the hard-decision forward error correction threshold with <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"> <mml:mrow class="MJX-TeXAtom-ORD"> <mml:mo>−</mml:mo> </mml:mrow> <mml:mrow class="MJX-TeXAtom-ORD"> <mml:mn>2</mml:mn> </mml:mrow> <mml:mspace width="thickmathspace"/> <mml:mrow class="MJX-TeXAtom-ORD"> <mml:mi mathvariant="normal">d</mml:mi> <mml:mi mathvariant="normal">B</mml:mi> <mml:mi mathvariant="normal">m</mml:mi> </mml:mrow> </mml:math> receiver optical power. The experimental results indicate that our proposed scheme is a promising candidate for the standardization of 400 GbE wavelength division multiplexing-based long-haul distance data center interconnects.