time-slot (multiplexed in the time domain). In this way, the OLT is receiving signals from only one ONU or ONT at any point in time. In the downstream direction, the OLT (usually) continuously transmits (or may burst transmit). ONUs or ONTs see their own data through the address labels embedded in the signal. DOCSIS Provisioning of EPON (DPoE) Data Over Cable Service Interface Specification (DOCSIS) Provisioning of Ethernet Passive Optical Network, or DPoE, is a set of Cable Television Laboratory specifications that implement the DOCSIS service layer interface on existing Ethernet PON (EPON, GEPON or 10G-EPON) Media Access Control (MAC) and Physical layer (PHY) standards. In short it implements the DOCSIS Operations Administration Maintenance and Provisioning (OAMP) functionality on existing EPON equipment. It makes the EPON OLT look and act like a DOCSIS Cable Modem Termination Systems (CMTS) platform (which is called a DPoE System in DPoE terminology). In addition to offering the same IP service capabilities as a CMTS, DPoE supports Metro Ethernet Forum (MEF) 9 and 14 services for the delivery of Ethernet services for business customers. Radio frequency over glass Radio frequency over glass (RFoG) is a type of passive optical network that transports RF signals that were formerly transported over copper (principally over a hybrid fibre-coaxial cable) over PON. In the forward direction RFoG is either a stand-alone P2MP system or an optical overlay for existing PON such as GEPON/EPON. The overlay for RFoG is based on wavelength-division multiplexing (WDM)—the passive combination of wavelengths on a single strand of glass. Reverse RF support is provided by transporting the upstream or return RF onto a separate wavelength from the PON return wavelength. The Society of Cable and Telecommunications Engineers (SCTE) Interface Practices Subcommittee (IPS) Work Group 5, is currently working on IPS 910 RF over Glass. RFoG offers backwards compatibility with existing RF modulation technology, but offers no additional bandwidth for RF based services. Although not yet completed, the RFoG standard is actually a collection of standardized options which are not compatible with each other (they cannot be mixed on the same PON). Some of the standards may interoperate with other PONs, others may not. It offers a means to support RF technologies in locations where only fiber is available or where copper is not permitted or feasible. This technology is targeted towards Cable TV operators and their existing HFC networks. WDM-PON Wavelength-Division Multiplexing PON, or WDM-PON,