In fiber-optic communications, wavelength-division multiplexing (WDM) is a technology which multiplexes a number of optical carrier signals onto a single optical fiber by using different wavelengths of laser light. This technique enables bidirectional communications over a single strand of fiber as well as multiplication of capacity.
Small Form-factor Pluggable (SFP) is a compact, hot-pluggable network interface module format used for both telecommunication and data communications applications. An SFP interface on networking hardware is a modular slot for a media-specific transceiver, such as for a fiber-optic cable or a copper cable. The advantage of using SFPs compared to fixed interfaces is that individual ports can be equipped with different types of transceivers as required, with the majority including optical line terminals, network cards, switches and routers.
A passive optical network (PON) is a fiber-optic telecommunications technology for delivering broadband network access to end-customers. Its architecture implements a point-to-multipoint topology in which a single optical fiber serves multiple endpoints by using unpowered (passive) fiber optic splitters to divide the fiber bandwidth among the endpoints. Passive optical networks are often referred to as the last mile between an Internet service provider (ISP) and its customers. Many fiber ISPs prefer this technology.
Optical Carrier transmission rates are a standardized set of specifications of transmission bandwidth for digital signals that can be carried on Synchronous Optical Networking (SONET) fiber optic networks. Transmission rates are defined by rate of the bitstream of the digital signal and are designated by hyphenation of the acronym OC and an integer value of the multiple of the basic unit of rate, e.g., OC-48. The base unit is 51.84 Mbit/s. Thus, the speed of optical-carrier-classified lines labeled as OC-n is n × 51.84 Mbit/s.
Physical medium dependent sublayers or PMDs further help to define the physical layer of computer network protocols. They define the details of transmission and reception of individual bits on a physical medium. These responsibilities encompass bit timing, signal encoding, interacting with the physical medium, and the properties of the cable, optical fiber, or wire itself. Common examples are specifications for Fast Ethernet, Gigabit Ethernet and 10 Gigabit Ethernet defined by the Institute of Electrical and Electronics Engineers (IEEE).
The physical-layer specifications of the Ethernet family of computer network standards are published by the Institute of Electrical and Electronics Engineers (IEEE), which defines the electrical or optical properties and the transfer speed of the physical connection between a device and the network or between network devices. It is complemented by the MAC layer and the logical link layer. An implementation of a specific physical layer is commonly referred to as PHY.
Ethernet in the first mile (EFM) refers to using one of the Ethernet family of computer network technologies between a telecommunications company and a customer's premises. From the customer's point of view, it is their first mile, although from the access network's point of view it is known as the last mile.
40 Gigabit Ethernet (40GbE) and 100 Gigabit Ethernet (100GbE) are groups of computer networking technologies for transmitting Ethernet frames at rates of 40 and 100 gigabits per second (Gbit/s), respectively. These technologies offer significantly higher speeds than 10 Gigabit Ethernet. The technology was first defined by the IEEE 802.3ba-2010 standard and later by the 802.3bg-2011, 802.3bj-2014, 802.3bm-2015, and 802.3cd-2018 standards. The first succeeding Terabit Ethernet specifications were approved in 2017.
An optical line termination (OLT), also called an optical line terminal, is a device which serves as the service provider endpoint of a passive optical network. It provides two main functions:
- to perform conversion between the electrical signals used by the service provider's equipment and the fiber optic signals used by the passive optical network.
- to coordinate the multiplexing between the conversion devices on the other end of that network.
ITU-T Recommendation G.983 is a family of recommendations that defines broadband passive optical network (BPON) for telecommunications Access networks. It originally comprised ten recommendations, G.983.1 through G.983.10, but recommendations .6–.10 were withdrawn when their content was incorporated into G.983.2. The current view is that the BPON standards are mature, and no further work will be done on them after the 2007 round. The GPON OMCI definition has been revised to stand alone, rather than citing G.983.2.
The passive optical network (PON) uses tree-like network topology. Due to the topology of PON, the transmission modes for downstream and upstream are different. For the downstream transmission, the OLT broadcasts optical signal to all the ONUs in continuous mode (CM), that is, the downstream channel always has optical data signal. One given ONU can find which frame in the CM stream is for it by reading the header of the frame. However, in the upstream channel, ONUs can not transmit optical data signal in CM. It is because that all the signals transmitted from the ONUs converge into one fiber by the power splitter, and overlap among themselves if CM is used. To solve this problem, burst mode (BM) transmission is adopted for upstream channel. The given ONU only transmits optical packet when it is allocated a time slot and it needs to transmit, and all the ONUs share the upstream channel in the time division multiple access (TDMA) mode. The phases of the BM optical packets received by the OLT are different from packet to packet, since the ONUs are not synchronized to transmit optical packet in the same phase, and the distance between OLT and given ONU are random. In order to compensate the phase variation from packet to packet, burst mode clock and data recovery (BM-CDR) is required. Such circuit can generate local clock with the frequency and phase same as the individual received optical packet in a short locking time, for example within 40 ns. Such generated local clock can in turn perform correct data decision. Above all, the clock and data recovery can be performed correctly after a short locking time.
The 10 Gbit/s Ethernet Passive Optical Network standard, better known as 10G-EPON allows computer network connections over telecommunication provider infrastructure. The standard supports two configurations: symmetric, operating at 10 Gbit/s data rate in both directions, and asymmetric, operating at 10 Gbit/s in the downstream direction and 1 Gbit/s in the upstream direction. It was ratified as IEEE 802.3av standard in 2009. EPON is a type of passive optical network, which is a point-to-multipoint network using passive fiber-optic splitters rather than powered devices for fan-out from hub to customers.
10 Gigabit Ethernet is a group of computer networking technologies for transmitting Ethernet frames at a rate of 10 gigabits per second. It was first defined by the IEEE 802.3ae-2002 standard. Unlike previous Ethernet standards, 10GbE defines only full-duplex point-to-point links which are generally connected by network switches; shared-medium CSMA/CD operation has not been carried over from the previous generations of Ethernet standards so half-duplex operation and repeater hubs do not exist in 10GbE. The first standard for faster 100 Gigabit Ethernet links was approved in 2010.
In telecommunications, radio frequency over glass (RFoG) is a deep-fiber network design in which the coax portion of the hybrid fiber coax (HFC) network is replaced by a single-fiber passive optical network (PON). Downstream and return-path transmission use different wavelengths to share the same fiber. The return-path wavelength standard is expected to be 1610 nm, but early deployments have used 1590 nm. Using 1590/1610 nm for the return path allows the fiber infrastructure to support both RFoG and a standards-based PON simultaneously, operating with 1490 nm downstream and 1310 nm return-path wavelengths.
Terabit Ethernet or TbE is Ethernet with speeds above 100 Gigabit Ethernet. The 400 Gigabit Ethernet and 200 Gigabit Ethernet standard developed by the IEEE P802.3bs Task Force using broadly similar technology to 100 Gigabit Ethernet was approved on December 6, 2017. On February 16, 2024 the 800 Gigabit Ethernet standard developed by the IEEE P802.3df Task Force was approved.
10G-PON is a 2010 computer networking standard for data links, capable of delivering shared Internet access rates up to 10 Gbit/s over existing dark fiber. This is the ITU-T's next generation standard following on from GPON or Gigabit-capable PON. Optical fibre is shared by many subscribers in a network known as FTTx in a way that centralises most of the telecommunications equipment, often displacing copper phone lines that connect premises to the phone exchange. Passive optical network (PON) architecture has become a cost-effective way to meet performance demands in access networks, and sometimes also in large optical local networks for "Fibre-to-the-desk".
G.fast is a digital subscriber line (DSL) protocol standard for local loops shorter than 500 meters, with performance targets between 100 Mbit/s and 1 Gbit/s, depending on loop length. High speeds are only achieved over very short loops. Although G.fast was initially designed for loops shorter than 250 meters, Sckipio in early 2015 demonstrated G.fast delivering speeds over 100 Mbit/s at nearly 500 meters and the EU announced a research project.
NG-PON2, Next-Generation Passive Optical Network 2 is a 2015 telecommunications network standard for a passive optical network (PON). The standard was developed by ITU and details an architecture capable of total network throughput of 40 Gbit/s, corresponding to up to 10 Gbit/s symmetric upstream/downstream speeds available at each subscriber.
Higher Speed PON is a family of ITU-T recommendations for data links, capable of delivering shared Internet access rates up to 50 Gbit/s. Higher Speed PON is the first PON system to use digital signal processing, succeeding both single-channel XGS-PON and multi-channel NG-PON2. It provides upgrade paths for legacy PON generations such as GPON, XG-PON, XGS-PON, and 10G-EPON.
