An OLT (Optical Line Terminal) is a key component in passive optical networks (PONs). It is typically located at the service provider's facility and is connected to the PON network. Some key functions of the OLT are:
Aggregating traffic - The OLT aggregates traffic from many end users onto the operator's core network. It acts as the central hub of a PON network.
Managing ONU connections - The OLT manages connections and traffic for many ONUs (Optical Network Units). It assigns upstream/downstream wavelengths to ONUs.
Delivering services - Using PON technology like GPON or XGS-PON, the OLT delivers high bandwidth services like internet, VoIP, IPTV to end users.
Uplink interfaces - OLTs have high capacity uplink ports like 10G or 100G Ethernet to connect to the operator's metro/core network.
Downlink PON ports - These ports connect to the passive optical distribution network using protocols like GPON, XGS-PON, EPON, 10G-EPON.
Power budgeting - The OLT manages the optical power budget between itself and connected ONUs. It sends signals downstream and receives upstream.
Layer 2 features - OLTs support Layer 2 functions like VLAN tagging, QoS, priority queuing for traffic management.
Equipment management - The OLT can be managed remotely by the operator's back office software via protocols like SNMP.
Service provisioning - The OLT provisions and activates subscriber services on specific ONUs based on commands from the management system.
Security - OLT provides security functions like encryption, access control, isolation between subscribers.
Control plane processor - This manages and configures the system, protocols, ONU connectivity, services etc.
Switch fabric - High capacity switching matrix to connect line cards and route traffic.
PON line cards - These provide the PON ports and optics to connect to the passive optical network. Modern OLTs support point-to-multipoint PON technologies like XGS-PON, GPON, EPON, 10G EPON.
Uplink line cards - These provide ports and optics for connectivity to metro or core networks. Common interfaces are 10G, 40G and 100G Ethernet.
Management and I/O interfaces - This includes ports for management, synchronization, console access, expansion etc.
Support for PON protocols like XGS-PON, XG-PON, GPON, EPON, 10G-EPON. Compliance with standards ensures interoperability.
Traffic management features like hierarchical QoS, queueing, shaping, policing.
Multicast support - IGMP snooping and proxy, video replication.
Security functions for access control lists, stateful firewalls etc.
Remote management using protocols like CLI, Netconf, SNMP and web UIs.
Orchestration integrations to activate on-demand services.
In summary, the OLT sits at the heart of passive optical access networks. It aggregates traffic, manages ONU connectivity, delivers high bandwidth services, supports advanced networking features, and enables remote management and orchestration. OLT capabilities like XGS-PON, low latency, fast protection switching, and software programmability enable next-gen access network applications.