Abstract
The coherent transmission technology using digital signal processing and advanced modulation formats, is bringing networks closer to the theoretical capacity limit of optical fibres, the Shannon limit. The in-phase/quadrature electro-optic modulator that encodes information on both the amplitude and the phase of light, is one of the underpinning devices for the coherent transmission technology. Ideally, such modulator should feature a low loss, low drive voltage, large bandwidth, low chirp and compact footprint. However, these requirements have been only met on separate occasions. Here, we demonstrate integrated thin-film lithium niobate in-phase/quadrature modulators that fulfil these requirements simultaneously. The presented devices exhibit greatly improved overall performance (half-wave voltage, bandwidth and optical loss) over traditional lithium niobate counterparts, and support modulation data rate up to 320 Gbit s−1. Our devices pave new routes for future high-speed, energy-efficient, and cost-effective communication networks.
Highlights
The coherent transmission technology using digital signal processing and advanced modulation formats, is bringing networks closer to the theoretical capacity limit of optical fibres, the Shannon limit
This technology is expected to penetrate into the rapidly growing, capacityhungry short reach links, such as metro and data-centre interconnects, where an in-phase/quadrature (IQ) modulator must be operated in a small space, while featuring low loss, low drive voltages, and large bandwidths[8,9,10]
Tremendous efforts have been made to realise small-footprint and high-performance IQ modulators in various material platforms, including silicon (Si), indium phosphide (InP), polymers, and plasmonics[15,16,17,18,19,20,21,22,23,24,25,26,27,28,29,30,31,32]. These platforms normally offer the advantages of compact footprints and large bandwidths, each type of modulator has its limitations, including large Vπ (Si), high optical loss, nonlinear response (InP), or doubts over long-term stability
Summary
The coherent transmission technology using digital signal processing and advanced modulation formats, is bringing networks closer to the theoretical capacity limit of optical fibres, the Shannon limit. The in-phase/quadrature electro-optic modulator that encodes information on both the amplitude and the phase of light, is one of the underpinning devices for the coherent transmission technology Such modulator should feature a low loss, low drive voltage, large bandwidth, low chirp and compact footprint. To keep up with this everincreasing demand, the digital coherent transmission technology has been introduced for long-haul communication links and is allowing networks to approach the maximum achievable capacity of optical fibres, known as the Shannon limit[3,4,5,6,7] This technology is expected to penetrate into the rapidly growing, capacityhungry short reach links, such as metro and data-centre interconnects, where an in-phase/quadrature (IQ) modulator must be operated in a small space, while featuring low loss, low drive voltages, and large bandwidths[8,9,10]. QPSK modulation up to 220 Gbit s−1 (110 Gbaud), and 16 QAM modulation up to 320 Gbit s−1 (80 Gbaud), are successfully demonstrated
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