Abstract
High sampling-rate digital-to-analog converters (DAC) are usually applied in optical fiber communication systems for the signal generation with advanced modulation formats such as four-level pulse amplitude modulation (PAM4). There exist various imperfections for high sampling-rate DACs. Clock tone leakage (CTL) is one of the imperfections and may seriously degrade the bit error rate (BER) performance, especially for single-carrier transmission systems. In this paper, we study a low-complexity time-domain averaging (TDA) based CTL compensation (TDA-CTLC) method for short-reach PAM4 transmission. By numerical simulation, we investigate the impacts of chromatic dispersion, CTL interference-to-signal power ratio (ISPR), and vertical resolution of the analog-to-digital converter on the BER performance. The results exhibit that the TDA-CTLC enabled PAM4 transmission system in the presence of a wide range of ISPR has a similar BER performance with the one without CTL interference. Moreover, we experimentally evaluate the compensation performance of the TDA-CTLC in a directly-modulated laser-based short-reach PAM4 transmission system. Up to −4 dB ISPR can be compensated with a slight BER performance degradation due to nonlinear distortions.
Highlights
Driven by upcoming high-speed services such as the Internet of Things, virtual reality, the fifthgeneration applications, and cloud computing, the ever-increasing bandwidth demands continue to fuel the need for faster physical transmission technologies with low cost and power consumption in data center interconnects (DCI) and access networks [1], [2]
The interfered PAM4 signal with an interference-to-signal power ratio (ISPR) of 0 dB is transmitted over 2-km single-mode fiber (SMF) link, the recovered signal is sampled by the analog-to-digital converter (ADC) with 8-bit resolution
We investigated a low-complexity time-domain averaging (TDA)-CTL compensation (CTLC) method for the short-reach PAM4 transmission system
Summary
Driven by upcoming high-speed services such as the Internet of Things, virtual reality, the fifthgeneration applications, and cloud computing, the ever-increasing bandwidth demands continue to fuel the need for faster physical transmission technologies with low cost and power consumption in data center interconnects (DCI) and access networks [1], [2]. A 2-tap least mean square(LMS) based adaptive notch filter was proposed and employed in both short-reach 100 Gbit/s PAM4 and DMT systems for CTL compensation (CTLC) [13], [15]. It requires massive multipliers for hardware implementation with high-level parallelism. In our previous work [16], two simple CTLC methods were proposed and experimentally investigated in a 100 Gbit/s DMT transmission system with 2-km single-mode fiber (SMF) link. We investigate the low-complexity online TDA-based CTLC method in a directly-modulated laser (DML) based short-reach PAM4 transmission system with IMDD for intra-DCI.
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