In telecommunications, the term access network indicates the part of the network intended for the connection between individual users and the switching center and more generally, the connection between a subscriber and their service provider. Its key components are the physical carriers and the central transmission equipment.



Asymmetric Digital Subscriber Line: Class of transmission technologies used for digital access to high-speed transmission over twisted pair, specifically in the last leg of the telephone network (or access network).

The ADSL is characterized by an asymmetric bandwidth: greater download (from 640 kbit / s to several tens of Mbit / s) lower in the upload (from 128 kbit / s to 1 Mbit / s).



Angled Physical Contact: Type of optical connector whose end face is characterized by a cut of about 8 °, rather than being perpendicular to the axis.
This cut reduces the reflection of light towards the apparatus generating the pulse. The APC offers the lowest return loss rate for high bandwidth applications and long haul links.



Loss of signal strength during transmission between two points. Expresses the overall loss of an optical system, measured in decibels at specific wavelengths.



The quantity of information that can be transmitted per unit of time in a physical mean of transport (fiber/copper).



As a mean of transmission of information signals used in electric communications, the coaxial cable consists of a single copper conductor at the center of the cable (core) and a dielectric element (insulator), which separates the central core from an external screen consisting of braided metal wires, ensuring the insulation between the two conductors. The metal shield helps to block electrical interferences.



Device used in optical fiber systems with one or more input fiber and one or several output fiber.  Its logical function is to allocate the power of a signal of an input connection between two or more output connections, and vice versa.



The location in which (where) the permutation of the signal generator from the unit to various customers occurs.



The decibel (one-tenth of a Bel) is the logarithmic unit of measurement used to express the relationship between two values ​​of homogeneous quantities. The logarithmic scale allows you to easily manage very large sizes with dynamics.



Physical phenomenon that accounts for the distortion that a signal undergoes as it passes through the transmission medium. The dispersion causes the attenuation and dilatation of the light pulses during their passage through an optical fiber.



Primary section of a fiber optic network (backbone) used to connect the most important nodes (cities, islands etc).



Dense Wave Division Multiplexing, a technique used to increase the transmission capacity of an optical fiber network. Multiple streams of information are sent within a single optical fiber to different wavelengths, thus minimizing interference between them.



Family of local technologies (LAN) and the protocols used to connect devices to a defined area.



A rigid element (ceramic) within the body of the connector that aligns and supports the fiber inside the connector.



A quantity that relates periodic phenomena or repetitive processes. The frequency is the number of events that are repeated in a given unit of time.  It is measured in Hertz, where 1 Hertz = 1 event per second.



Fiber to the Building:  A fiber connection from the central platform to the base of a building, in which there is a beam splitter.



Fiber To The Cabinet:  A fiber connection from the central platform to cabinets of individual homes. The connection is via a coaxial cable or twisted pair.



Fiber to the home:  A fiber connection from the central platform to the home of the user. Is the link that provides more bandwidth to the end user.



Fiber To The X: “X” meaning “building”, “cabinet,” “curb”, “premise” ;  the last node in which it is present along the fiber network.



A unit of frequency equal to one billion events per second 109Hz.



Unlike the ADSL data transmission system, which is an asymmetrical system, the HDSL (High Bit Rate Digital Subscriber) system is a symmetrical system that allows to transmit data with the same bandwidth in both download and upload.

INDEX OF REFRACTION (Or Refractive Index)

The relationship between the speed of light in vacuum or isolation, and the speed of light in a specific material or substance.  The refractive index of a material is a dimensionless quantity that quantifies the decrease in speed of propagation of the electromagnetic radiation, when it passes through a material.



The signal loss of power following the insertion of a component in an optical circuit (for example, the loss due to the presence of a coupling in an optical network).



Network protocol which belongs to the Internet protocol suite TCP / IP port on which the operation of the Internet is based. IP is a protocol in which information is sectioned into small packets, which travel separately across the network, and then are reunified by the information receiving device.



International Telecommunications Union: the UN agency that assists in the development and coordination of worldwide technical standards for telecommunications).



Light Amplification by Stimulated Emission of Radiation:  A device capable of emitting a beam of coherent monochromatic and concentrated light in a highly collimated beam straight, through the process of stimulated emission. The laser brightness is very high compared to traditional light sources. The use of laser in optical fibers is due to the peculiarity of emitting a large optical power in a few square microns.


LED (Light Emitting Diode)

A device used in a transmitter for converting optical information into electrical information. The LEDs have large spectrum widths.


LSZH (Low Smoke Zero Halogen)

An abbreviation used in cables that do not contain halogens, and that, in the event of fire, guarantee a very limited production of opaque smoke and toxic gases which are harmful and corrosive.



The last mile refers to the final leg of the access network, i.e. the network that extends between the data center or provider and the end user. Also called the local loop, can experience limitations when composed of copper wire.



Method used in telecommunications wherein multiple analog or digital signals are combined into a single transmission medium. Many different signals can be sent within the same wire, with different wavelengths.


OLT (Optical Line Termination)

An apparatus present in data centers that has the dual purpose of converting the signal from electrical to optical of the various systems of the service provider (Telecom Italy, Vodafone etc), and coordinating the multiplexing.



Multimode fiber New definition:

OM1: 62.5 fibers / 125

OM2: 50/125

OM3: 50/125 of high quality that can carry 10 Gb Ethernet data rates up to a maximum length of 300m.

OM4: 50/125 multimode fibers of the highest quality suitable to carry up to 10 Gb Ethernet at a maximum distance of 550m.


OTDR (Optical Time Domain Reflectometer)

An instrument that assesses the performance over time of the reflected component of the signal by sending a short pulse of light into the fiber and observing the backscattered light. Analysis by optical reflectometer allows the user to evaluate the length and overall attenuation of the fiber, including the presence of joints, couplings and mitigations that they introduce. One can also find a complete break of the optical transmission line and estimate the distance from the point of analysis.



Transducer device that converts an optical signal at a given wavelength into an electrical signal.



A type of network architecture in optical fiber, characterized by the presence of a fiber coming from the central platform that is split along the path into more fibers, through the use of splitters. It is an optical network in tree structure, in which each user receives a portion of the signal, according to the number of splitters present along the network (the lower the number of splitters, the less signal).

This is distinguished from the “point to point” network, in which each user has a dedicated network derived from the central platform (with obvious advantages in terms of available bandwidth).



Type of fiber optic network architecture in which each user has a fiber connection dedicated to them, derived  from the Central platform. This architecture is more expensive than the PON but allows greater bandwidth capacity and is customizable for each user.



In computing and telecommunications, POP (Point of Presence) is a network access point (router), provided by an Internet Service Provider (ISP), that can route traffic to the end users connected to it (individuals and small organizations).



Internet Service Provider or  ISP  (or simply ‘provider’ when used in computer context), is a commercial structure or organization that offers users (residential or business) internet services by contract , principally access to Internet and e-mail.



Return loss is the loss of signal power resulting from imperfections generated at the discontinuities in a line of optical fiber transmission. It is measured in dB at specific wavelengths.



A router  is an electronic device which, in a packet switched computer network, is responsible for routing data, subdivided into packets between different networks.



VDSL is a DSL technology that achieves high transmission speeds using DSL technology. It is therefore an enhancement of classical ADSL, whose data travel through copper. For very short distances, less than 300 meters, it is possible to have a connection at 26 Mbit / s symmetric or 52 Mbit / s downstream or download and 12 Mbit / s in the transmission or upload.

A variant of VDSL, called VDSL2, is currently used by Telecom Italy in FTTC (Fiber to cabinet).



The wavelength measures the distance between any point of a wave to the corresponding point on the next wave, from crest to crest for example.  The wavelength determines the nature of the various forms of radiant energy that comprise the electromagnetic spectrum (the color of light).
Wavelengths used in optical fiber communications are measured in nanometers (nm) and are related to frequencies of infrared rays: 850 nm (the first window), 1300 nm (second window) and 1550 nm (third window).