1. Field
This disclosure is generally related to a passive optical network (PON). More specifically, this disclosure is related to a PON in a Multi-Dwelling Unit (MDU) environment.
2. Related Art
The large bandwidth of an optical fiber has enabled access-service providers to deliver triple-play (video, voice, and high-speed data) services to single family units (SFUs) over a passive optical network (PON). Typically, PONs are used in the “first mile” of the network, which provides connectivity between the service provider's central offices and the premises of the customers. The “first mile” is generally a logical point-to-multipoint network, where a central office serves a number of customers. For example, a PON can adopt a tree topology, wherein one trunk fiber couples the central office to a passive optical splitter/combiner. Through a number of branch fibers, the passive optical splitter/combiner divides and distributes downstream optical signals to customers and combines upstream optical signals from customers (see FIG. 1). Note that other topologies, such as ring and mesh topologies, are also possible.
Transmissions within a PON are typically performed between an optical line terminal (OLT) and optical network units (ONUs). The OLT generally resides in the central office and couples the optical access network to a metro backbone, which can be an external network belonging to, for example, an Internet service provider (ISP) or a local exchange carrier. The ONU can reside in the residence of the customer and couples to the customer's own home network through a customer-premises equipment (CPE).
To deliver services to SFUs, the service provider installs an optical line terminal (OLT) in a central office and an ONU at each home. FIG. 1 presents a diagram illustrating a PON including a central office and a number of SFUs coupled through optical fibers and a passive optical splitter (prior art). A passive optical splitter 102 and optical fibers couple the SFUs to a central office 101. Passive optical splitter 102 can reside near end-user locations to minimize the initial fiber deployment costs. Central office 101 can couple to an external network 106, such as a metropolitan area network operated by an Internet service provider (ISP). Although FIG. 1 illustrates a tree topology, a PON can also be based on other topologies, such as a logical ring or a logical bus. Note that, although in this disclosure many examples are based on Ethernet PONs (EPONs), embodiments of the present invention are not limited to EPONs and can be applied to a variety of PONs, such as ATM PONs (APONs), gigabit PONs (GPONs, which are PONs using a variant of a generic framing protocol), and wavelength division multiplexing (WDM) PONs.
The SFU approach becomes difficult in a Multi-Dwelling Unit (MDU) environment. An MDU can be an apartment building, condominium, hotel, or other buildings that are subdivided into multiple residences. MDU presents challenging requirements to access service providers, such as maintenance of secure and stable communications among all subscribers, service isolation to prevent inter-service congestion, and provisioning and enforcement of service level agreements for sensitive traffic such as cellular backhaul (often found on rooftops). Additionally, it is often impractical to replace the building communication infrastructure. Hence, current MDU solutions often utilize existing copper wiring within the building for delivering high bandwidth triple-play services to individual customers. Within a PON, such an MDU approach relies on an ONU that is capable of supporting multiple subscribers (users). An MDU-enabled ONU can provide interfaces for the fiber connection to the OLT located at the central office along with multiple copper wire connections to individual residences.