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. 2020 Apr 27;9:71. doi: 10.1038/s41377-020-0272-5

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© The Author(s) 2020

Open Access This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The images or other third party material in this article are included in the article’s Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article’s Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/.

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Fig. 3 — a Light-microscope image of the Tx assembly, realized according to the concept shown in Fig. 1a. The array of Mach-Zehnder modulators (MZMs) is connected to an array InP-based HCSEL (“Laser array”) and to an array of single-mode fibres by PWBs (not visible here); see Fig. 1b, c. The launch powers, measured in the single-mode fibre for maximum transmission of the modulators, are sufficient for transmission over distances typical for data centre and campus-area networks, without the need of optical amplifiers. Launch power variations are mainly attributed to non-ideal coupling to and from the SiP chip; see the Methods section for details. Channel 6* contains an additional on-chip 3 dB splitter for testing, which leads to additional loss; see the Methods section. b Experimental setup for transmission demonstrations using different modulation formats and distances. An arbitrary-waveform generator (AWG) is used to drive the MZMs. In our demonstration, the modulators are operated sequentially via an RF probe delivering the drive signal at the input and another RF probe to provide a 50 Ω termination at the output. The optical signal is sent through up to 10 km of standard SMF and is detected with a photoreceiver that contains a photodetector along with a high-speed transimpedance amplifier. A real-time oscilloscope is used to capture the electric signals for subsequent offline processing. c Eye diagrams for transmission over various distances, with different modulation formats and symbol rates. As expected from the launch powers, Channel 8 shows the widest-open eyes, whereas Channel 6 is distorted by noise. d Estimated bit error ratios (BERs) for transmission over various distances, with different modulation formats and symbol rates. For all experiments, the BER stays below the 7% HD-FEC threshold. The aggregate module line rate amounts to a 448 Gbit/s. Results from back-to-back transmission experiments as well as measured BERs can be found in Supplementary Section S2