Abstract
Client-side optics are facing an ever-increasing upgrading pace, driven by upcoming 5G related services and datacenter applications. The demand for a single lane data rate is soon approaching 200 Gbps. To meet such high-speed requirement, all segments of traditional intensity modulation direct detection (IM/DD) technologies are being challenged. The characteristics of electrical and optoelectronic components and the performance of modulation, coding, and digital signal processing (DSP) techniques are being stretched to their limits. In this context, we witnessed technological breakthroughs in several aspects, including development of broadband devices, novel modulation formats and coding, and high-performance DSP algorithms for the past few years. A great momentum has been accumulated to overcome the aforementioned challenges. In this article, we focus on IM/DD transmissions, and provide an overview of recent research and development efforts on key enabling technologies for 200 Gbps per lane and beyond. Our recent demonstrations of 200 Gbps short-reach transmissions with 4-level pulse amplitude modulation (PAM) and discrete multitone signals are also presented as examples to show the system requirements in terms of device characteristics and DSP performance. Apart from digital coherent technologies and advanced direct detection systems, such as Stokes–vector and Kramers–Kronig schemes, we expect high-speed IM/DD systems will remain advantageous in terms of system cost, power consumption, and footprint for short reach applications in the short- to mid- term perspective.
Highlights
INTENSITY modulation direct detection (IM/DD) technology had been the dominating solution in all segments of fiberoptic communication networks since its first generation
We have experimentally explored the potential of using FFE and decision-feedback equalizer (DFE) for 200 Gbps/lane IM/DD transmissions with PAM4, and our experimental setup is shown in Figure 3 [71]
Advanced modulation formats, coding, and digital signal processing (DSP) schemes can improve the system efficiency and transmission performance, to further push forward the single lane rate with given system bandwidth. With such a significant progress during the past years, it is expected that novel technology candidates will converge into feasible solutions to fulfill the requirements for future high-speed client-side optics, where IM/DD transmissions are still dominating
Summary
INTENSITY modulation direct detection (IM/DD) technology had been the dominating solution in all segments of fiberoptic communication networks since its first generation. These hybrid schemes can be categorized as advanced direct-detection solutions [16] These schemes effectively employ complex vector modulation and/or polarization division multiplexing in a self-coherent manner to improve the transmission data rate and distance, and have shown a certain level of potentials as a way to forward in some application scenarios. These advanced DD schemes can be treated as a compromise between the digital coherent and IM/DD solutions, having a clear tradeoff between the transmission performance and system complexity.
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