Optical Communication Capacity and Quality to Maximize End-user TCP/IP Throughput

We present an analytic characterization of the steady-state throughput for end-users via optical cable systems when the signal-to-noise ratio (SNR) of the optical communication is given. Our model captures the effect of end-users' transmission control protocols (TCPs) and optical transport systems. We consider various TCPs, namely ultra-high-speed TCPs (UHS-TCPs), high-speed TCPs, and traditional TCPs. For the optical cable systems, we consider forward error correction (FEC), quadrature amplitude modulation, wavelength division multiplexing. We show that the robustness of UHS-TCP against errors enables cable systems to have an additional 2-dB SNR margin, which will provide extra capacity. The evaluation results show that total user throughput by UHS-TCP can be maximized when the optical communication enables some signal errors to remain for users, so-called post-FEC errors. Our model also predicts that the working 100-Tbps transpacific cable FASTER can be upgraded to 130 Tbps when it accepts a smaller margin for error-free service. Further, the model estimates FASTER will be able to provide 160-Tbps service when UHS-TCP is applied.