Upstream transmission of WDM/OCDM-PON in a loop-back configuration with remotely supplied short optical pulses

We propose and experimentally demonstrate upstream transmission in a wavelength division multiplexing/optical code division multiplexing (WDM/OCDM) passive optical network (PON) without using any high-cost devices such as mode-locked lasers or LiNbO
₃
external modulators. To make optical network units (ONUs) simple, a loop-back transmission of short optical pulses for OCDM in upstream transmission was investigated. The quality of the short optical pulses, remotely supplied via 23 km of single-mode fiber (SMF), was sufficient for 4-chip OCDM encoding at the ONUs.2WDM/4OCDM signals, generated by multiplexing four OCDM signals using the same wavelength as well as another signal with a different wavelength, showed error-free transmission (bit error rate BER <; 10
^-9
) over a 23 km SMF at 1.25 Gb/s.