The relationship between OLT, ONU, and ODN in the access network is shown in the figure below. The OLT will collect the information passed by the core network and process it to the ODN, while the information passed by the ONU through the ODN will be collected and processed to the core network. ODN provides optical transmission channels for OLT and. ConceptONU (Optical Network Unit) is a client-side device in the optical network, placed at the client side and used in conjunction with OLT. ONU provides services such as data, IPTV (Internet Protocol Television), and voice (Integrated Access Device), and realizes Ethernet Layer 2 and Layer 3 functions.Functions1. Select to receive the data sent by OLT. 2. Respond to the commands sent by OLT and adjust accordingly. 3. Cache the user's Ethernet data and send the user's Ethernet data to the OLT. 4. User and service multiplexing function: assembling information from each user; connecting individual service interfaces. 5. Transmission multiplexing function: analyze the signals transmitted from the ODN and take out the part belonging to the ONU and arrange the information to be sent to the ODN in a reaso. ConceptODN (Optical Distribution Network) is an optical cable network based on PON equipment. ODN mostly adopts P2MP (point 2 multiple point) topology, as shown in the figure below. There are more nodes in the ODN network and the network management is complicated, so the construction cost of the ODN network is relatively high, up to 50%~70% of the overall investment.FunctionsTo provide optical transmission channels for OLT and ONU. ODN includes five parts: feeder segments, optical distribution points, wiring segments, optical access points, and in-home segments, as shown in the following figure. Feeder section: The feeder section is from the ODF (optical distribution frame) of the local office to the fiber optic cable distribution point. The feeder section is used as the backbone cable to achieve long-distance coverage. Wiring section: From the distribution point. ConceptOLT (Optical Line Terminal) refers to the terminal equipment used to connect fiber optic trunk lines. OLT is equivalent to a switch or router in a traditional communication network. The OLT is also capable of bandwidth allocation for different users' QoS/SLA requirements.FunctionsUplink the upper layer network to complete the uplink access of PON (Passive Optical Network); converge the signals from various services and transmit them to end users according to a certain format. Through the ODN network, it connects the user terminal equipment ONU; sends the signals from users into various service networks according to the service types; and realizes the functions of control, management, and ranging for ONU. OLT can be divided into three parts: core part, service part, an.
