Time division multiplexing (TDM-PON) systems such as BPON and GPON are currently deployed to bring broadband services to subscribers globally. Although traditional TDM based PONs combine the high capacity of optical fiber and the low maintenance cost of a passive outside plant infrastructure, this architecture has severe limitations in speed, distance and number of subscribers, due to power losses associated with passive splitter and the bandwidth sharing.

As more broadband applications appear, demands from end-users will soon outgrow the capacity of systems being deployed today and upgrading TDM-based optical access networks will be a major challenge. There is consensus in the industry that WDM is the ideal solution to extend the capacity of optical networks without drastically changing the currently deployed fiber infrastructure. WDM-PON can provide a virtual point-to-point link to each end-user over a PON without complicated MAC protocols, that simplifies tasks of network management, protection, and security to the level of traditional point-to-point networks.

Fig. 1

The biggest hurdle for WDM-PON is not technical but economic. WDM-PON delivers a single wavelength both upstream and downstream to a single home or office- a task that can be accomplished today using wavelength-specific distributed feedback (DFB) lasers or tunable lasers. However, it’s simply cost prohibitive to locate a DFB laser at every residence. One of the critical technology breakthroughs required to enable the mass deployment WDM-PON systems is the generation of multiple wavelengths from a compact and cost effective laser source.

Peleton’s MCLAs represent the ideal solution and can be effectively deployed as a seed source in a number of WDM-PON architectures. Two OLT architectures utilizing MCLA light source are shown in Fig. 1 and 2. At the OLT, each channel can be modulated using Reflective Semiconductor Optical Amplifiers (RSOA) or injection locked Fabry-Perot lasers, and then the channels can be routed from the OLT to the appropriate ONUs and backward by a wavelength demultiplexing/multiplexing device located at the splitting point. By using RSOA at the ONU, the same wavelength channel may be used for upstream and downstream communication simultaneously, allowing universal colorless ONUs to be deployed. Because of the very high quality laser performance provided by MCLAs, many options for modulation format and speed can be implemented..

Fig 2.