A passive optical network (PON) is a system for providing network access over “the last mile.” The PON is a point to multi-point network comprised of an optical line terminal (OLT) at a central office, an optical distribution network (ODN), and a plurality of optical network units (ONUs) at the customer premises. Downstream data transmissions may be broadcast to all of the ONUs, while upstream data transmissions may be transmitted to the OLT using various multiple access techniques, such as time division multiple access (TDMA), wavelength division multiple access (WDMA), and frequency division multiple access (FDMA). These multiple access technologies ensure transmissions from the ONUs are received by the OLT without conflicting with one another. The per-user capacity of TDMA-based PONs is inversely proportional to the number of ONUs, partially because the time between one ONU completing its transmission and the next ONU starting transmission, known as the turnaround time, may only allow the transmission speed to scale up to a certain point without any data loss.
WDMA systems use multiple wavelengths of a light to carry multiple data signals. Each of the wavelengths may be assigned to one of the ONUs, allowing for a point-to-point communication path from the ONU to the OLT. The multiple wavelength carrier signals are multiplexed onto an optical fiber before reaching the OLT. The components of a WDMA-based PON system are typically more costly and complex than TDMA PON system components, in part because WDMA PONs use high-precision lasers, optical couplers, optical amplifiers, optical filters, and optical splitters.