Google Research

Long-Reach Wavelength-Routed TWDM PON: Technology and Deployment

  • Adam Edwin Taylor Barratt
  • Cedric Lam
  • Claudio DeSanti
  • Daoyi Wang
  • Joy Jiang
  • Junyan Geng
  • Liang Du
  • Shuang Yin
  • Tao Zhang
  • Xiangjun Zhao
Journal of Lightwave Technology (2019)


Abstract—We present a long-reach wavelength-routed time-wavelength division multiplexing (TWDM) passive optical network (PON) architecture (LRWR-PON) and its commercial implementation, that supports up to 768 users per fiber strand and up to 50 km transmission distance. The increased reach allows central offices to become more flexible and fewer in quantity, while the increased aggregation reduces the size and number of optical cables needed, enabling smaller trenches to be used. LRWR-PON also contains eight additional point-to-point wavelengths on each fiber to support wireless sites and/or high-speed dedicated bandwidth applications, greatly simplifying converged network designs. Multiple new optical components and modules have been developed to implement our novel architecture. These include a Cyclic Arrayed Waveguide Grating to passively aggregate and distribute access wavelengths in the field, an integrated optical amplifier and multiplexer combination device to aggregate optical line terminal (OLT) channels and extend the system reach, several dense wavelength division multiplexing OLT optics, and a colorless time- wavelength division multiplexing optical network terminal employing ultra-low cost tunable burst-mode lasers. Our analysis shows the simplification of the civil construction enabled by LRWR-PON greatly outweighs the increased optical component complexity. To date, we have conducted a successful field trial with 606 real-life customers for more than 9 months and we have been rolling out this system in new Google Fiber markets for production services.

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