Conference paper Open Access

Scaling single-wavelength optical interconnects to 180 Gb/s with PAM-M and pulse shaping

Stefanos Dris; Paraskevas Bakopoulos; Nikolaos Argyris; Christos Spatharakis; Hercules Avramopoulos


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{
  "publisher": "Zenodo", 
  "DOI": "10.5281/zenodo.290544", 
  "title": "Scaling single-wavelength optical interconnects to 180 Gb/s with PAM-M and pulse shaping", 
  "issued": {
    "date-parts": [
      [
        2016, 
        3, 
        7
      ]
    ]
  }, 
  "abstract": "<p>Faced with surging datacenter traffic demand, system designers are turning to multi-level optical modulation with direct detection as the means of reaching 100 Gb/s in a single optical lane; a further upgrade to 400 Gb/s is envisaged through wavelength-multiplexing of multiple 100 Gb/s strands. In terms of modulation formats, PAM-4 and PAM-8 are considered the front-runners, striking a good balance between bandwidth-efficiency and implementation complexity. In addition, the emergence of energy-efficient, high-speed CMOS digital-to-analog converters (DACs) opens up new possibilities: Spectral shaping through digital filtering will allow squeezing even more data through low-cost, low-bandwidth electro-optic components. In this work we demonstrate an optical interconnect based on an EAM that is driven directly with sub-volt electrical swing by a 65 GSa/s arbitrary waveform generator (AWG). Low-voltage drive is particularly attractive since it allows direct interfacing with the switch/server ASIC, eliminating the need for dedicated, power-hungry and expensive electrical drivers. Single-wavelength throughputs of 180 and 120 Gb/s are experimentally demonstrated with 60 Gbaud optical PAM-8 and PAM-4 respectively. Successful transmission over 1250 m SMF is achieved with direct-detection, using linear equalization via offline digital signal processing in order to overcome the strong bandwidth limitation of the overall link (~20 GHz). The suitability of Nyquist pulse shaping for optical interconnects is also investigated experimentally with PAM-4 and PAM-8, at a lower symbol rate of 40 Gbaud (limited by the sampling rate of the AWG). To the best of our knowledge, the rates achieved are the highest ever using optical PAM-M formats.</p>", 
  "author": [
    {
      "family": "Stefanos Dris"
    }, 
    {
      "family": "Paraskevas Bakopoulos"
    }, 
    {
      "family": "Nikolaos Argyris"
    }, 
    {
      "family": "Christos Spatharakis"
    }, 
    {
      "family": "Hercules Avramopoulos"
    }
  ], 
  "type": "paper-conference", 
  "id": "290544"
}
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