Editing Hybrid fiber-coaxial

{{Short description|Telecommunications industry term}}
{{Use American English|date=March 2021}}
{{Use mdy dates|date=March 2021}}
{{Multiple issues|{{Lead too short|date=November 2012}}
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'''Hybrid fiber-coaxial''' ('''HFC''') is a [[broadband]] [[telecommunications network]] that combines [[optical fiber]] and [[coaxial cable]]. It has been commonly employed globally by [[cable television]] operators since the early 1990s.<ref name="auto6">{{Cite book|url=https://books.google.com/books?id=z-cObR6WnMkC&dq=hfc+network+one+way&pg=PA2|title=Broadband Cable Access Networks: The HFC Plant|first1=David|last1=Large|first2=James|last2=Farmer|date=November 25, 2008|publisher=Morgan Kaufmann|isbn=978-0-08-092214-0 |via=Google Books}}</ref>

In a hybrid fiber-coaxial cable system, television channels are sent from the cable system's distribution facility, the [[Cable television headend|headend]], to local communities through [[optical fiber]] subscriber lines.  At the local community, an [[optical node]] translates the signal from a light beam to [[radio frequency]] (RF), and sends it over [[coaxial cable]] lines for distribution to subscriber residences.<ref>{{cite web|url=https://archive.nanog.org/sites/default/files/08-Noll.pdf|title=Hybrid Fiber-Coaxial Networks: Technology and Challenges in Deploying Multi-Gigabit Access Services|website=nanog.org|access-date=30 March 2023|author=Kevin A. Noll}}</ref> The fiber optic trunk lines provide enough bandwidth to allow additional bandwidth-intensive services such as [[cable internet access]] through [[DOCSIS]].<ref>Data-Over-Cable Service Interface Specifications
DOCSIS® 3.1
CCAP™ Operations Support System Interface 
Specification
CM-SP-CCAP-OSSIv3.1-I25-220819</ref> Bandwidth is shared among users of an HFC.<ref>{{cite book | url=https://books.google.com/books?id=4mUkzG0P6fQC&dq=pon+shared+bandwidth&pg=PA184 | isbn=978-1-931695-37-4 | title=Achieving the Triple Play: Technologies and Business Models for Success: Comprehensive Report | date=March 15, 2024 | publisher=Intl. Engineering Consortiu }}</ref> Encryption is used to prevent eavesdropping.<ref>Data-Over-Cable Service Interface Specifications
DOCSIS® 3.0
MAC and Upper Layer Protocols Interface
Specification
CM-SP-MULPIv3.0-C01-171207
</ref> Customers are grouped into service groups, which are groups of customers that share bandwidth among each other since they use the same [[Television channel frequencies|RF channels]] to communicate with the company.

==Description==
[[Image:HFC Network Diagram.svg|thumb|upright=2.0|A common HFC architecture]]
The fiber optic network extends from the cable operators' master [[Cable television headend|headend]], sometimes to regional headends, and out to a neighborhood's hubsite, and finally to an optical to coaxial cable node which typically serves 25 to 2000 homes. A master headend will usually have [[satellite dish]]es for reception of distant video signals as well as [[Internet Protocol|IP]] aggregation [[Router (computing)|router]]s. Some master headends also house [[telephony]] equipment (such as automatic [[telephone exchange]]s) for providing telecommunications services to the community. In an HFC network telephony is provided using [[PacketCable]].

A regional or area headend/hub will receive the video signal from the master headend<ref>{{cite web |author1=Emil Stoilov |title=On The Design of Hybrid Fiber-Coax Networks |url=http://ecet.ecs.uni-ruse.bg/cst06/Docs/cp/SIII/IIIA.6.pdf |publisher=International Conference on Computer Systems and Technologies |access-date=16 May 2023 |year=2006}}</ref> and add to it the [[public, educational, and government access]] (PEG) [[cable TV]] channels as required by local franchising authorities or insert targeted advertising that would appeal to a local area, along with internet from a [[Cable modem termination system|CMTS]] (an Integrated CMTS, which includes all parts required for operation), or a CCAP which provides both internet and video.

Separate Edge QAMs can be used to provide [[Quadrature amplitude modulation|QAM]] modulated video suitable for transmission in a coaxial cable network, from digital video sources.<ref>[https://www.cablefax.com/Assets/CT_QAM_Supplement_100108(3).pdf CT's EDGE QAM Tech Guide]. ''cablefax.com.'' Retrieved 18 October 2024</ref><ref>[https://people.computing.clemson.edu/~jmarty/papers/JCM81839_new.pdf QAM Resource Allocation in Mixed-Format VoD Systems]. ''people.computing.clemson.edu.'' Retrieved 19 October 2024</ref> Edge QAMs can also be connected to a CMTS to provide internet data instead of video, in a modular CMTS architecture.<ref>{{cite web |last1=Chapman |first1=John |title=THE MODULAR CMTS ARCHITECTURE |url=http://www.nctatechnicalpapers.com/Paper/2005/2005-the-modular-cmts-architecture/download |access-date=2 March 2024}}</ref><ref>{{cite web |title=TRANSITIONING TO M-CMTS |url=https://www.nctatechnicalpapers.com/Paper/2006/2006-transitioning-to-m-cmts/download |access-date=2 March 2024}}</ref> CCAPs aim to replace the conventional, integrated CMTS which only provides data and Edge QAMs used for video which are separate pieces of equipment.<ref>{{Cite web|url=https://www.lightwaveonline.com/network-design/article/16658207/the-evolution-of-ccap|title=StackPath|website=www.lightwaveonline.com|date=September 13, 2013 }}</ref>

Video can be encoded according to standards such as NTSC, MPEG-2, DVB-C or the [[QAM (television)|QAM standard]] and data according to DOCSIS, analog video can be scrambled,<ref>[https://www.worldradiohistory.com/Archive-Communications-Technology/80s/Communications-Technology-1984-09.pdf Communications Technology 1984-09]. ''worldradiohistory.com.'' Retrieved 18 October 2024</ref> signals can be [[modulated]] by analog or digital video modulators including QAM modulators<ref>{{Cite book|url=https://books.google.com/books?id=tvUoQJXEwNEC&q=cable+analog+modulator|title=Modern Cable Television Technology|first=Walter S.|last=Ciciora|date=March 7, 2004|publisher=Morgan Kaufmann|isbn=978-1-55860-828-3 |via=Google Books}}</ref> or  edge QAMs for video and/or data depending on whether a modular CMTS is used, at the CMTS for data only,<ref>{{cite book | url=https://books.google.com/books?id=anbLBQAAQBAJ&dq=transmitter+rf+management+cable&pg=PA537 | isbn=978-1-4200-3066-2 | title=Broadband Last Mile: Access Technologies for Multimedia Communications | date=October 3, 2018 | publisher=CRC Press }}</ref><ref>{{cite web | url=https://www.cisco.com/c/en/us/td/docs/cable/cmts/config_guide/b_cmts_ds_us_features/b_cmts_ds_us_features_chapter_0100.html | title=Cisco CMTS Router Downstream and Upstream Features Configuration Guide - DOCSIS 2.0 A-TDMA Modulation Profiles for the Cisco CMTS Routers &#91;Support&#93; }}</ref><ref>{{cite web | url=https://www.cisco.com/c/en/us/support/docs/broadband-cable/radio-frequency-rf-hybrid-fiber-coaxial-hfc/23710-mod-profile.html | title=Configuring Cable Modulation Profiles on Cisco CMTSS }}</ref> or at the CCAP for video and data, and upconverted onto RF [[carrier wave|carriers]] in this equipment.

The various services from CMTSs, CCAPs, Edge QAMs and QAM modulators are combined onto a single RF electrical signal using headend RF management modules such as splitters and combiners<ref>{{Cite web |last1=Swanson |first1=Al |last2=Mayer |first2=Gary |last3=Hartman |first3=Bill |title=Meeting the Needs of the Headend-of-the-Future Today--The Structured Headend |url=https://www.nctatechnicalpapers.com/Paper/1996/1996-meeting-the-needs-of-the-headend-of-the-future-today-the-structured-headend/download |website=www.nctatechnicalpapers.com}}</ref><ref>{{cite web | url=https://books.google.com/books?id=_6EzSt-xXJIC&dq=headend+rf+management+module&pg=PA14 | title=_6EzSt-xXJIC }}</ref><ref>{{cite book | url=https://books.google.com/books?id=QOFWx2umt8sC&dq=headend+rf+management&pg=PA407 | isbn=978-0-08-051193-1 | title=Modern Cable Television Technology | date=January 13, 2004 | publisher=Elsevier }}</ref> and the resulting signals are inserted into a broadband optical transmitter which in practice is a transmitter module in an "optics platform" or headend platform such as an Arris CH3000, Scientific Atlanta Prisma, or a Cisco Prisma II.<ref name="nctatechnicalpapers.com">{{Cite web |last=Downey |first=John J. |title=The Power of Distributed Access Architectures (DAA) Benefits of Digital Fiber Along with Remote-PHY |url=https://www.nctatechnicalpapers.com/Paper/2020/2020-the-power-of-distributed-access-architectures/download |website=www.nctatechnicalpapers.com}}</ref><ref>{{Cite web |title=ARRIS CH3000 |url=https://www.normann-engineering.com/products/product_pdf/optical_transmission/arris/EN_CH3000.pdf |website=www.normann-engineering.com}}</ref> 

[[File:Streamer Anevia CityPlay Amiens (2).jpg|thumb|Top: video encoder, decoder and multiplexer, Bottom: Edge QAM turns video in IP packets over Ethernet from the device above and other devices, to RF QAM signals ready to be transmitted]]
[[File:CMTS Arris Cadant C4 CityPlay Amiens.jpg|thumb|CMTS provides internet on an HFC network and has RF connections on the rear <ref>Arris E6000 manual https://fccid.io/ANATEL/01759-14-07236/Manual-E6000/50DAF2B5-F106-42DF-A563-6008357AC079/PDF</ref>]]
[[File:Multiplexeurs câble coaxial CityPlay Amiens.jpg|thumb|MAXNET RF management: combiner and splitter modules for RF signals in coaxial cables, just before they are sent to the transmitter]]
[[File:Convetisseur fibre-coaxial Scientific Atlanta CityPlay Amiens.jpg|thumb| Scientific Atlanta Prisma II chassis with transmitter modules, converts RF signals in coaxial cables into optical signals in fiber optics and amplifies them]]
[[File:Convetisseur fibre-coaxial Scientific Atlanta CityPlay Amiens (arrière).jpg|thumb|Scientific Atlanta HDRx chassis with many receiver modules for receiving data from customers, which is their internet upload bandwidth in this case in an HFC coaxial network, it converts optical signals in fiber optics into RF signals in coaxial cables]]


These platforms host several transmitters and receivers the latter of which can be used for cable internet, and can also host Erbium-Doped Fiber Amplifiers (EDFAs) to extend the reach of the optical signals in fiber optics.<ref>{{Cite web |last1=Pidgeon |first1=Rezin E. |last2=Frymyer |first2=Don E. |title=Optical Amplifier Basic Properties And System Modeling: A Simple Tutorial |url=https://www.nctatechnicalpapers.com/Paper/1992/1992-optical-amplifier-basic-properties-and-system-modeling-a-simple-tutorial/download |website=www.nctatechnicalpapers.com}}</ref><ref>{{Cite web |title=Prisma 1550 nm Strand Mounted Optical Amplifier |url=https://www.cisco.com/c/dam/en/us/products/collateral/video/prisma-strand-mounted-optical-amplifier/product_data_sheet0900aecd806c3af2.pdf |website=www.cisco.com}}</ref> Each transmitter and receiver services one optical node.<ref>{{Cite web |last=Sniezko |first=Oleh J. |title=MULTI-LAYER HEAD END COMBINING NETWORK DESIGN FOR BROADCAST, LOCAL, AND TARGETED SERVICES |url=https://www.nctatechnicalpapers.com/Paper/1997/1997-multi-layer-head-end-combining-network-design-for-broadcast-local-and-targeted-services/download |website=www.nctatechnicalpapers.com}}</ref>

This optical transmitter converts the RF electrical signal to a downstream optically modulated signal that is sent to the nodes. Fiber optic cables connect the headend or hub to the optical nodes in a [[point-to-point (network topology)|point-to-point]] or [[star network|star]] [[network topology|topology]],<ref>{{Cite book|url=https://books.google.com/books?id=qUhZDwAAQBAJ&q=coaxial+cable+network|title=Hybrid Fiber-Optic Coaxial Networks: How to Design, Build, and Implement an Enterprise-Wide Broadband HFC Network|first=Ernest|last=Tunmann|date=January 1, 1995|publisher=CRC Press|isbn=978-1-4822-8107-1 |via=Google Books}}</ref> or in some cases, in a protected [[ring network|ring]] topology. Each node can be connected via its own dedicated fiber,<ref>{{cite book | url=https://books.google.com/books?id=tvUoQJXEwNEC&dq=optical+node+dedicated+fiber+ncta&pg=PA19 | title=Modern Cable Television Technology | isbn=978-1-55860-828-3 | last1=Ciciora | first1=Walter S. | date=March 10, 2024 | publisher=Morgan Kaufmann }}</ref> so fiber optic cables laid outdoors in the [[outside plant]] can have several<ref>{{cite book | url=https://books.google.com/books?id=QOFWx2umt8sC&dq=high+fiber+count+cable+point+to+point+star&pg=PA743 | title=Modern Cable Television Technology | isbn=978-0-08-051193-1 | last1=Large | first1=David | last2=Farmer | first2=James | date=January 13, 2004 | publisher=Elsevier }}</ref> dozen to several hundred or even thousands of fibers, an extreme example being 6912 fibers.<ref>{{cite web | url=https://www.thefoa.org/tech/ref/cable/HighFiberCountCables.html | title=The FOA Reference for Fiber Optics - High Fiber Count Cables }}</ref>

{{multiple image | align = right | direction = vertical | width = 150
| image1 = Fiber optic node.jpg | caption1 = An optical node with a fiber splice case (black)
| image2 = HFC trunk amplifier.jpg | caption2 = A trunk amplifier
| image3 = HFC line extender.jpg | caption3 = A distribution amplifier (line extender)
| image4 = HFC taps.jpg | caption4 = A series of taps (servicing multiple rooms in a hotel) from a distribution line or "trunk" with [[electrical termination|terminators]] on unused ports
| image5 = Arris TG2482 cable modem.jpg| caption5 = Cable modem, also called a router or gateway with coaxial cable connection to an HFC network on the bottom left using a threaded [[F connector]]
}}

=== Fiber optic nodes ===
A fiber optic node has a broadband optical receiver, which converts the downstream optically modulated signal coming from the headend or hub to an electrical signal going to the customers. {{As of|2015|post=,}} the downstream signal is a RF modulated signal that typically begins at 50&nbsp;MHz and ranges from 550 to 1000&nbsp;MHz on the upper end. The fiber optic node also contains a reverse- or return-path transmitter that sends communication from customers back to the headend. In North America, this reverse signal is a modulated RF ranging from 5–42&nbsp;MHz while in other parts of the world, the range is 5–65&nbsp;MHz. This electrical signal is then outputted through coaxial cable to form a coaxial trunk.

The optical portion of the network provides a large amount of flexibility. If there are not many fiber-optic cables to the node, [[wavelength division multiplexing]] can be used to combine multiple optical signals onto the same fiber. Optical filters are used to combine and split optical wavelengths onto the single fiber. For example, the downstream signal could be on a wavelength at 1550&nbsp;nm and the return signal could be on a wavelength at 1310&nbsp;nm.<ref>{{Cite web |title=MODEL NC4000EG C4000EG OPTICAL NODE SERIES (NC), ESSENTIAL FEATURES FIBER DEEP NODE PLATFORM |url=https://www.goamt.com/wp-content/uploads/2017/05/NC4000EG_OPTICAL-NODE-SERIES_AMT.pdf |archive-url=https://web.archive.org/web/20210423055904/https://www.goamt.com/wp-content/uploads/2017/05/NC4000EG_OPTICAL-NODE-SERIES_AMT.pdf |archive-date=2021-04-23 |website=www.goamt.com}}</ref><ref>{{Cite web |title=Cable Technician Pocket Guide |url=https://www.commscope.com/globalassets/digizuite/1695-cable-technician-pocket-guide.pdf |website=www.commscope.com}}</ref>

=== Final connection to customers ===
The coaxial trunk portion of the network connects 25–2000 homes (500 is typical)<ref>{{Cite web|url=https://books.google.com/books?id=7xcEAAAAMBAJ&dq=optical+node+coaxial+cable&pg=PA35|title=Network World|date=August 5, 1996|publisher=IDG Network World Inc|via=Google Books}}</ref> in a tree-and-branch configuration off of the node.<ref>{{Cite book|url=https://books.google.com/books?id=qUhZDwAAQBAJ&dq=hfc+network+tree&pg=PT117|title=Hybrid Fiber-Optic Coaxial Networks: How to Design, Build, and Implement an Enterprise-Wide Broadband HFC Network|first=Ernest|last=Tunmann|date=January 1, 1995|publisher=CRC Press|isbn=978-1-4822-8107-1 |via=Google Books}}</ref><ref>{{Cite book|url=https://books.google.com/books?id=E2IHjQUutjUC&dq=hfc+network+2000&pg=PA282|title=Local Access Network Technologies|first=Paul|last=France|date=January 30, 2004|publisher=IET|isbn=978-0-85296-176-6 |via=Google Books}}</ref>

Trunk coaxial cables are connected to the optical node<ref>{{Cite web |last=Schmitt |first=Matt |title=Cable Network Overview |url=https://www.ieee802.org/3/epoc/public/mar12/schmitt_01_0312.pdf |website=www.ieee802.org}}</ref><ref>{{Cite book|url=https://books.google.com/books?id=z-cObR6WnMkC&dq=optical+node+coaxial+cable&pg=PA216|title=Broadband Cable Access Networks: The HFC Plant|first1=David|last1=Large|first2=James|last2=Farmer|date=November 25, 2008|publisher=Morgan Kaufmann|isbn=978-0-08-092214-0 |via=Google Books}}</ref> and form a coaxial backbone to which smaller distribution cables connect. RF [[amplifier]]s called trunk amplifiers are used at intervals in the trunk to overcome cable attenuation and passive losses of the electrical signals caused by splitting or "tapping" the coaxial cable. Trunk cables also carry AC power which is added to the cable line at usually either 60 or 90 V by a power supply (with a lead acid backup battery inside) and a power inserter. The power is added to the cable line so that optical nodes, trunk and distribution amplifiers do not need an individual, external power source.<ref>{{Cite web |last=Noll |first=Kevin A. |title=Hybrid Fiber-Coaxial Networks: Technology and Challenges in Deploying Multi-Gigabit Access Services |url=https://archive.nanog.org/sites/default/files/08-Noll.pdf |website=archive.nanog.org}}</ref> The power supply might have a [[electricity meter|power meter]] next to it depending on local power company regulations.

From the trunk cables, smaller distribution cables are connected to a port of one of the trunk amplifiers called a bridger to carry the RF signal and the AC power down individual streets. Usually trunk amplifiers have two output ports: one for the trunk, and another as a bridger. Distribution amplifiers (also called system amplifiers) can be connected from a bridger port 
to connect several distribution cables to the trunk if more capacity is needed as they have multiple output ports. Alternatively, line extenders, which are smaller distribution amplifiers with only one output port, can be connected to the distribution cable coming off the bridger port in the trunk and used to boost the signals in the distribution cables<ref name="auto5">{{cite book | url=https://books.google.com/books?id=z-cObR6WnMkC&dq=hfc+line+extender+distribution+amplifier&pg=PA361 | title=Broadband Cable Access Networks: The HFC Plant | isbn=978-0-08-092214-0 | last1=Large | first1=David | last2=Farmer | first2=James | date=November 25, 2008 | publisher=Morgan Kaufmann }}</ref> to keep the power of the television signal at a level that the TV can accept. The distribution line is then "tapped" into and used to connect the individual drops to customer homes.<ref>{{cite web | url=https://broadbandlibrary.com/taps-a-peek-under-the-hood/ | title=Taps: A Peek Under the Hood &#124; | date=November 20, 2021 }}</ref>

These RF taps pass the RF signal and block the AC power unless there are telephony devices that need the back-up power reliability provided by the coax power system.<ref>{{Cite book|url=https://books.google.com/books?id=z-cObR6WnMkC&q=hfc+network&pg=PA2|title=Broadband Cable Access Networks: The HFC Plant|first1=David|last1=Large|first2=James|last2=Farmer|date=November 25, 2008|publisher=Morgan Kaufmann|isbn=978-0-08-092214-0 |via=Google Books}}</ref> The tap terminates into a small coaxial drop using a standard screw type connector known as an [[F connector]].

The drop is then connected to the house where a ground block protects the system from stray voltages. Depending on the design of the network, the signal can then be passed through a splitter to multiple TVs or to multiple set top boxes (cable boxes) which may then be connected to a TV. If too many splitters are used to connect multiple TVs, the signal levels will decrease, and picture quality on analog channels will decrease. The signal in TVs past those splitters will lose quality and require the use of a "drop" or "house" amplifier to restore the signal.<ref>{{cite book | url=https://books.google.com/books?id=dLdovRLxm4oC&dq=cable+television+house+amplifier&pg=PA144 | isbn=978-90-5199-400-1 | title=Broadband Access and Network Management: NOC '98 - Networks and Optical Communication | date=March 2, 1998 | publisher=IOS Press }}</ref>

=== Evolution of HFC networks ===
Historically the trend among cable operators has been to reduce the amount of coaxial cable used in their networks to improve signal quality, which initially led to the adoption of HFC.<ref>{{cite book | url=https://books.google.com/books?id=dRhHPINWo2AC&dq=cmts+coaxial&pg=PA533 | title=Networks: Internet, Telephony, Multimedia : Convergences and Complementarities | isbn=978-2-7445-0144-9 | last1=Hardy | first1=Daniel | date=March 2, 2024 | publisher=Springer }}</ref> HFC replaced coaxial cable networks which had coaxial trunk cables originating at the headend of the network, and HFC replaced part of these trunk cables with fiber optic cables and optical nodes. In these coaxial networks, trunk amplifiers were placed along the trunk cables to maintain adequate signal levels in the trunks,<ref>{{Cite book|url=https://books.google.com/books?id=M31W_U3ev3MC&q=coaxial+cable+network|title=Delivering Internet Connections over Cable: Breaking the Access Barrier|first1=Mark E.|last1=Laubach|first2=David J.|last2=Farber|first3=Stephen D.|last3=Dukes|date=February 28, 2002|publisher=John Wiley & Sons|isbn=978-0-471-43802-1 |via=Google Books}}</ref><ref>{{Cite web |title=THE COMPLETE TECHNICAL PAPER PROCEEDINGS |url=https://www.nctatechnicalpapers.com/Paper/1998/downloadyear/pdf |website=www.nctatechnicalpapers.com}}</ref> distribution feeder cables could be used to distribute signals from the trunks into individual streets,<ref>{{cite book | url=https://books.google.com/books?id=CqhYCwAAQBAJ&dq=headend+5+trunk+cables&pg=PA102 | title=Head's Broadcasting in America: A Survey of Electronic Media (1-download) | isbn=978-1-317-34793-4 | last1=McGregor | first1=Michael A. | last2=Driscoll | first2=Paul D. | last3=McDowell | first3=Walter | date=January 8, 2016 | publisher=Routledge }}</ref><ref>{{cite book | url=https://books.google.com/books?id=OJqjBQAAQBAJ&dq=headend+5+trunk+cables&pg=SA24-PA4 | title=TV & Video Engineer's Reference Book | isbn=978-1-4831-9375-5 | last1=Jackson | first1=K. G. | last2=Townsend | first2=G. B. | date=May 15, 2014 | publisher=Elsevier }}</ref><ref>{{cite book | url=https://books.google.com/books?id=epBIhmdsfxMC&dq=headend+5+trunk+cables&pg=PA73 | title=Communication Technology Update | date=April 22, 1993 | publisher=Taylor & Francis | isbn=978-0-240-80881-9 }}</ref> directional couplers were used to improve signal quality,<ref>{{Cite web |title=TV & Communications - December 1964 |url=https://www.worldradiohistory.com/Archive-TV-%26-Communications/TV-and-Communications/TV%26C-1964-12.pdf |website=www.worldradiohistory.com}}</ref> trunk amplifiers could be equipped with automatic level control or automatic gain control,<ref>{{cite web | url=https://www.nctatechnicalpapers.com/Paper/1980/1980-distribution-equipment-for-400-mhz-co-axial-communications-systems | title=Paper - Distribution Equipment for 400 MHZ Co-Axial Communications Systems - NCTA Technical Papers }}</ref> hybrid amplifiers, which have a [[hybrid integrated circuit]]<ref name="piedmontscte.org">{{Cite web |last=Young |first=Conrad |title=RFMD.® CATV Hybrid Amplifier Modules: Past, Present, Future |url=https://www.piedmontscte.org/resources/CATV%2BHybrid%2BAmplifier%2BModules%2BPast%242C%2BPresent%242C%2BFutureWP.pdf |website=www.piedmontscte.org}}</ref><ref>{{cite journal | url=https://ieeexplore.ieee.org/document/4065085 | doi=10.1109/TCATV.1978.285736 | title=Reliability Considerations in CATV Hybrids | date=1978 | last1=Grant | first1=Al | last2=Eachus | first2=Jim | journal=IEEE Transactions on Cable Television | volume=CATV-3 | issue=1 | pages=1–23 | s2cid=6899727 | url-access=subscription }}</ref> could also be used,<ref>{{cite web | url=https://www.nctatechnicalpapers.com/Paper/1983/1983-the-design-approach-to-a-new-catv-distribution-amplifier | title=Paper - the Design Approach to a New CATV Distribution Amplifier - NCTA Technical Papers }}</ref> and separate bridgers were used to connect the trunk to distribution feeders.<ref>{{cite web | url=https://www.nctatechnicalpapers.com/Paper/1981/1981-performance-of-a-400-mhz-54-channel-cable-television-distribution-system | title=Paper - Performance of a 400 MHZ, 54 Channel, Cable Television Distribution System - NCTA Technical Papers }}</ref><ref>{{cite web | url=https://www.nctatechnicalpapers.com/Paper/1981/1981-the-design-construction-cost-and-performance-the-first-400-mhz-cable-television-system | title=Paper - the Design, Construction, Cost and Performance the First 400 MHZ Cable Television System - NCTA Technical Papers }}</ref><ref>{{cite book | url=https://books.google.com/books?id=c0z7d9S82EsC&dq=cable+Trunk+bridger&pg=PA206 | title=Data and Computer Communications: Networking and Internetworking | isbn=978-1-4200-4131-6 | last1=Hura | first1=Gurdeep S. | last2=Singhal | first2=Mukesh | date=March 28, 2001 | publisher=CRC Press }}</ref>

In 1953, [[C-COR]] was the first to introduce cable powering which transmits power through coaxial cables for powering cable amplifiers.  In 1965, it introduced the use of [[integrated circuits]] in [[amplifiers]] used on [[utility pole]]s and in 1969 was the first to use [[heat sink|heat fins]] on amplifiers.<ref>{{Cite web|url=https://books.google.com/books?id=0S5msp1NMJYC&q=c+cor+1969+heat+fins|title=TV Communications|date=March 11, 1975|publisher=Communications Publishing Corporation|via=Google Books}}</ref><ref name="auto8">{{Cite web |last=Taylor |first=Archer S. |title=HISTORY BETWEEN THEIR EARS |url=https://syndeoinstitute.org/wp-content/uploads/2022/12/HistoryBetweenTheirEars-TaylorArcherS.pdf |website=syndeoinstitute.org}}</ref> The first amplifiers in outdoor housings with hinges and seals, for installation between utility poles hanging from messenger wires, were offered in 1965.<ref>{{Cite web |title=TV & Communications - September 1965 |url=https://www.worldradiohistory.com/Archive-DX/DX-Horizons/1965/TV%26C-1965-09.pdf |website=www.worldradiohistory.com}}</ref> In around 1973, hubs began to be used in cable networks to increase signal quality as a result of network expansion, and cable operators made efforts to reduce the number of amplifiers in cascade on coaxial parts of the network from around 20 to 5.<ref name="auto7">{{Cite web |title=Communications Technology - December 1991 |url=https://www.worldradiohistory.com/Archive-Communications-Technology/90s/Communicaation-Technology-1991-12.pdf |website=www.worldradiohistory.com}}</ref><ref>{{Cite web |last=Chadwick |first=Russell B. |title=A SURVEY OF TECHNICAL REQUIREMENTS FOR BROADBAND CABLE TELESERVICES VOLUME 3 |url=https://files.eric.ed.gov/fulltext/ED084875.pdf |website=files.eric.ed.gov}}</ref> Supertrunks made of coaxial cable with FM modulated video signals,<ref>{{cite web | url=https://books.google.com/books?id=3CFnCaaJ5-EC&dq=fm+supertrunk+coaxial+cable&pg=PA73 | title=A Study of the Technical and Feasibility of Providing Narrowband and Broadband Communications Service in Rural Areas Volume 1 }}</ref><ref name="auto8"/> fiber optics or microwave links were used to connect headends to hubs.<ref>{{cite journal | url=https://onlinelibrary.wiley.com/doi/abs/10.1002/dac.4510030404 | doi=10.1002/dac.4510030404 | title=CATV fibre-optic supertrunking: A comparison of parameters and topologies using analog and/Or digital techniques | date=1990 | last1=Borelli | first1=Vincent R. | last2=Gysel | first2=Hermann | journal=International Journal of Digital & Analog Communication Systems | volume=3 | issue=4 | pages=305–310 | url-access=subscription }}</ref><ref>{{cite web | url=https://www.nctatechnicalpapers.com/Paper/1985/1985-fiber-optic-technology-for-catv-supertrunk-applications | title=Paper - Fiber Optic Technology for CATV Supertrunk Applications - NCTA Technical Papers }}</ref><ref>{{Cite web |title=Communications Engineering and Design - December 1987 |url=https://www.worldradiohistory.com/Archive-C-ED/80s/C-ED-1987-12.pdf |website=www.worldradiohistory.com}}</ref><ref name="auto7"/> Fiber optics were first used as a supertrunk in 1976.<ref>{{Cite web |title=The Cable History Timeline |url=https://syndeoinstitute.org/wp-content/uploads/2022/10/CableTimelineFall2015.pdf |website=syndeoinstitute.org}}</ref> FM video could be also carried in fiber optics,<ref>{{cite web | url=https://books.google.com/books?id=ghplX-Fm2C0C&dq=fm+supertrunk+coaxial+cable&pg=PA279 | title=Broadband '89 | date=March 12, 2024 }}</ref> and fiber optics eventually replaced coaxial cables in supertrunks.<ref name="auto8"/>  Bandwidth in cable networks increased from 216&nbsp;MHz to 300&nbsp;MHz in the 1970s,<ref name="piedmontscte.org"/> to 400&nbsp;MHz in the 1980s,<ref name="auto8"/><ref name="ReferenceA">{{Cite web |title=THE COMPLETE TECHNICAL PAPER PROCEEDINGS 1991 |url=https://www.nctatechnicalpapers.com/Paper/1991/downloadyear/pdf |website=www.nctatechnicalpapers.com}}</ref><ref>{{Cite web |title=Communications Engineering Digest - May 1981 |url=https://www.worldradiohistory.com/Archive-C-ED/80s/C-ED-1981-05.pdf |website=www.worldradiohistory.com}}</ref> to 550&nbsp;MHz, 600&nbsp;MHz and 750&nbsp;MHz in the 1990s,<ref name="ReferenceA"/><ref>{{cite web | url=https://www.nctatechnicalpapers.com/Paper/1996/1996-upgrade-of-450-550-mhz-cable-systems-to-600-mhz-using-a-phase-area-approach | title=Paper - Upgrade of 450/550 MHZ Cable Systems to 600 MHZ Using a Phase Area Approach - NCTA Technical Papers }}</ref><ref>{{Cite web |last=McNamara |first=D. |last2=Fukasawa |first2=Y. |last3=Wakabayashi |first3=Y. |last4=Shirakawa |first4=Y. |last5=Kakuta |first5=Y. |title=750MHz Power Doubler and Push-Pull CATV Hybrid Modules Using Gallium Arsenide |url=https://www.nctatechnicalpapers.com/Paper/1996/1996-750mhz-power-doubler-and-push-pull-catv-hybrid-modules-using-gallium-arsenide/download |website=www.nctatechnicalpapers.com}}</ref> and to 870&nbsp;MHz in the year 2000.<ref name="ReferenceB">{{Cite web |last=Jones |first=Doug |title=DOCSIS® 4.0 Technology Realizing Multigigabit Symmetric Services - Migration Scenarios for Multigigabit Return Services |url=https://www.nctatechnicalpapers.com/Paper/2019/2019-docsis-4-0-technology-realizing-multigigabit-symmetric-services/download |website=www.nctatechnicalpapers.com}}</ref>

To cope with needs for increased digital bandwidth such as for DOCSIS internet, cable operators have implemented expansions in the RF spectrum in HFC networks beyond 1&nbsp;GHz to 1.2&nbsp;GHz,<ref>{{cite web |last1=Ouyang |first1=Tao |title=Cable Lifespan Extension with FDX & ESD |url=https://www.itu.int/en/ITU-T/studygroups/2017-2020/09/Wuhan-WSP/Documents/08-NG-Cable.pdf |website=www.itu.int/ |access-date=2 March 2024}}</ref><ref>{{cite web | url=https://www.broadbandtechreport.com/docsis/article/14174609/atx-looks-to-docsis-40-and-beyond | title=ATX looks to DOCSIS 4.0 and beyond | date=April 22, 2020 }}</ref> have transitioned to only handling IP traffic in the network thus eliminating dedicated video RF channels, used digital transport adapters (DTAs) for transmitting normally analog signals, or used Switched Digital Video (SDV)<ref>{{cite web | url=https://www.ncta.com/whats-new/the-switch-to-switched-digital-video | title=The Switch to Switched Digital Video &#124; NCTA — the Internet & Television Association }}</ref><ref name="auto2">{{cite web |title=Lessons from Operating Tens of Thousands of Remote PHY Devices |url=https://www.nctatechnicalpapers.com/Paper/2021/2021-lessons-from-operating-tens-of-thousands-of-remote-phy-devices/download |publisher=SCTE |access-date=2 March 2024}}</ref> which allows the number of television channels in coaxial cables to be reduced without reducing the number of channels that are offered.<ref>{{Cite web |last=Baumgartner |first=Jeff |date=2008-06-01 |title=Who Makes What: Switched Digital Video |url=https://www.lightreading.com/business-management/who-makes-what-switched-digital-video |website=www.lightreading.com}}</ref><ref>{{cite web | url=https://www.broadbandtechreport.com/video/article/16448319/switched-ip-video-technology-frees-up-to-80-of-bandwidth-for-docsis-expansion | title=Switched IP Video Technology Frees up to 80% of Bandwidth for DOCSIS Expansion | date=June 30, 2017 }}</ref>

Towards the end of the 1990s GaAs (Gallium Arsenide) transistors were introduced in HFC nodes and amplifiers, replacing silicon transistors which allowed an expansion of the spectrum used in HFC from 870&nbsp;MHz to 1&nbsp;GHz by 2006.<ref name="ReferenceB"/> GaN transistors, introduced in 2008<ref name="piedmontscte.org"/> and adopted in the 2010s allowed for another expansion to 1.2&nbsp;GHz, or for expansion from 550&nbsp;MHz to 750&nbsp;MHz in older networks to 1&nbsp;GHz without changing the spacing between amplifiers.<ref>{{Cite web |last=Sniezko |first=Oleh |last2=Combs |first2=Doug |last3=Brockett |first3=Rei |title=DISTRIBUTED DIGITAL HFC ARCHITECTURE EXPANDS BI-DIRECTIONAL CAPACITY |url=https://www.nctatechnicalpapers.com/Paper/2013/2013-distributed-digital-hfc-architecture-expands-bi-directional-capacity/download |website=www.nctatechnicalpapers.com}}</ref><ref>{{Cite web |last=Miguelez |first=Phil |title=Hi Ho, Hi Ho, to a Gigabit We Go - Positioning the HFC Network for the New Gigabit Era |url=https://www.nctatechnicalpapers.com/Paper/2016/2016-hi-ho-hi-ho-to-a-gigabit-we-go/download |website=www.nctatechnicalpapers.com}}</ref><ref>{{Cite web |last=Miguelez |first=Phil |last2=Slowik |first2=Fred |last3=Eastman |first3=Stuart |title=REFUELING THE CABLE PLANT – A NEW ALTERNATIVE TO GAAS |url=https://www.nctatechnicalpapers.com/Paper/2010/2010-refueling-the-cable-plant-a-new-alternative-to-gaas/download |website=www.nctatechnicalpapers.com}}</ref>

Remote PHY is an evolution of the HFC network that aims to reduce the use of coaxial cable in the network and improve signal quality. In a conventional HFC network, headend equipment such as CMTSs and CCAPs are connected to the HFC network using RF interfaces which physically are coaxial cable connections<ref>{{cite book | url=https://books.google.com/books?id=QOFWx2umt8sC&q=cmt&pg=PA249 | title=Modern Cable Television Technology | isbn=978-0-08-051193-1 | last1=Large | first1=David | last2=Farmer | first2=James | date=January 13, 2004 | publisher=Elsevier }}</ref><ref>{{cite web |title=E6000™ Converged Edge Router User Documentation |url=https://fccid.io/ANATEL/01759-14-07236/Manual-E6000/50DAF2B5-F106-42DF-A563-6008357AC079/PDF |access-date=2 March 2024}}</ref><ref>{{cite web | url=https://broadbandlibrary.com/out-of-band/ | title=Demystifying OOB and R-PHY &#124; | date=November 24, 2018 }}</ref> and optical signals in fiber optic cables in the network are analog. In Remote PHY, equipment such as CMTSs or CCAPs are connected directly to the HFC network using fiber optics carrying digital signals, eliminating the RF interface and coaxial cables at the CMTS/CCAP and RF modulation at the headend,<ref name="auto"/> and replacing analog signals in fiber optic cables in the network, with digital signals such as 10 Gigabit Ethernet signals,<ref name="nctatechnicalpapers.com"/> which eliminate the need for calibrating the HFC network bi-annually, extends the reach of the network, reduces the cost of equipment and maintenance,<ref>{{cite web | url=https://www.nctatechnicalpapers.com/Paper/2015/2015-evolution-of-cmts-ccap-architectures/ | title=Paper - Evolution of CMTS/CCAP Architectures - NCTA Technical Papers }}</ref> and improves signal quality and allows for modulation such as 4096 QAM instead of 1024 QAM, allowing more information to be transmitted at a time, per bit. This requires more sophisticated optical nodes which can also convert signals from digital to analog performing modulation, unlike conventional optical nodes which only need to convert signals from optical to electrical.<ref name="auto">{{cite web |last1=Jorge |first1=Salinger |title=Remote PHY: Why and How |url=https://www.nctatechnicalpapers.com/Paper/2014/2014-remote-phy-why-and-how/download |publisher=SCTE |access-date=2 March 2024}}</ref> These devices are known as Remote PHY devices (RPDs) or Remote MACPHY devices (RMDs). RPDs come in shelf variants which can be installed in apartment buildings (MDUs, multi dwelling units) and can also be installed in optical nodes or at a small hub which distributes signals similarly to a conventional HFC network.<ref name="nctatechnicalpapers.com"/><ref name="auto2"/><ref name="auto4">{{cite web |last1=Chapman |first1=John |title=DOCSIS Remote PHY Modular Headend Architecture (MHA v2) |url=https://www.cisco.com/c/dam/en/us/solutions/ns341/ns522/ns791/workshop_remote_phy_chapman_paper.pdf |publisher=SCTE |access-date=2 March 2024}}</ref><ref name="auto5"/><ref>{{cite web |title=Cisco Remote-PHY Compact Shelf Hardware Installation Guide |url=https://www.cisco.com/c/en/us/td/docs/cable/remote-phy-devices/installation/guide/b_cbr_rphy_shelf_hardware_install_guide.pdf |publisher=Cisco Systems, Inc. |access-date=2 March 2024}}</ref> Alternatively Remote PHY can allow for a CMTS/CCAP to be located in a remote data center away from customers.<ref name="auto1">{{cite web |title=Impact of CCAP to CM Distance in a Remote PHY Architecture |url=http://bowe.id.au/michael/isp/DOCSIS/collected-references/2015-impact-of-ccap-to-cm-distance-in-a-remote-phy-architecture%20(1).pdf |access-date=2 March 2024}}</ref>

Remote MACPHY, besides achieving the same purpose as Remote PHY, also moves all DOCSIS protocol functionality to the optical node or the outside plant, which can reduce latency when compared to Remote PHY.<ref name="auto3">{{cite web | url=https://www.nctatechnicalpapers.com/Paper/2021/2021-from-integrated-ccap-or-ccap-remote-phy-to-fma-with-remote-macphy | title=Paper - Follow the Yellow Brick Road: From Integrated CCAP or CCAP + Remote PHY to FMA with Remote MACPHY - NCTA Technical Papers }}</ref><ref>{{cite journal | url=https://ieeexplore.ieee.org/document/7959596 | title=Performance Comparison of R-PHY and R-MACPHY Modular Cable Access Network Architectures  | doi=10.1109/TBC.2017.2711145 | s2cid=3668345 | date=2018 | last1=Alharbi | first1=Ziyad | last2=Thyagaturu | first2=Akhilesh S. | last3=Reisslein | first3=Martin | last4=Elbakoury | first4=Hesham | last5=Zheng | first5=Ruobin | journal=IEEE Transactions on Broadcasting | volume=64 | pages=128–145 | url-access=subscription }}</ref> Remote CMTS/Remote CCAP builds upon this by moving all CMTS/CCAP functionality to the outside plant.<ref name="auto4"/><ref name="auto1"/> Distributed Access Architecture (DAA) covers Remote PHY and Remote MACPHY and has as the goal, moving functions closer to end customers, allowing for easier capacity expansions as centralized facilities for equipment are downsized or potentially eliminated, and newer DOCSIS versions beyond DOCSIS 3.1 with higher speeds. Remote PHY allows for some reuse of existing equipment such as CMTSs/CCAPs by replacing components.<ref name="auto3"/><ref>{{cite web | url=https://broadbandlibrary.com/so-you-want-to-be-a-docsis-engineer-youre-sure-about-this/ | title=So, You Want to be a DOCSIS Engineer? You're Sure About This? &#124; | date=February 17, 2023 }}</ref>

Virtual CCAPs (vCCAPs) or virtual CMTSs (vCMTSs) are implemented on commercial off the shelf x86-based servers with specialized software,<ref>{{Cite web|url=https://www.lightreading.com/cable-technology/harmonic-s-cableos-now-connected-to-18-4m-modems|title=Harmonic's 'CableOS' now connected to 18.4M modems}}</ref> are often implemented alongside DAA<ref>{{cite web |title=Practical Lessons of a DAA Deployment with a Virtualized CMTS |url=https://www.nctatechnicalpapers.com/Paper/2019/2019-practical-lessons-of-a-daa-deployment-with-a-virtualized-cmts/download |publisher=SCTE•ISBE |access-date=2 March 2024}}</ref> and can be used to increase service capacity without purchasing new CMTS/CCAP chassis, or add features to the CMTS/CCAP more quickly.<ref name="auto2"/>

Improving internet speeds for customers can be carried out by reducing the number of service groups with subscribers from 500 subscribers to no more than 128, in what is known as a n+0 architecture, with a single node and no amplifiers.<ref>{{cite web |title=Distributed Access Architecture Is Now Widely Distributed – And Delivering On It's Promise |url=https://www.nctatechnicalpapers.com/Paper/2021/2021-distributed-access-architecture-is-now-widely-distributed/download |publisher=SCTE |access-date=2 March 2024}}</ref><ref>{{cite web | url=https://www.broadbandtechreport.com/docsis/article/14174199/next-generation-hfc-part-1-upgrading-the-hfc-network | title=Next-Generation HFC Part 1 – Upgrading the HFC Network | date=April 15, 2020 }}</ref><ref name="auto"/> HFC networks operating at 1.8&nbsp;GHz<ref>{{Cite web |last=Foroughi |first=Nader |title=Upgrading the Plant to Satisfy Traffic Demands - The One Touch Approach |url=https://www.nctatechnicalpapers.com/Paper/2019/2019-upgrading-the-plant-to-satisfy-traffic-demands/download |website=www.nctatechnicalpapers.com}}</ref> to 3&nbsp;GHz have been explored with GaN transistors.<ref>{{cite web |title=2019 Blueprint for 3 ghz 25 gbps|url=https://www.nctatechnicalpapers.com/Paper/2019/2019-blueprint-for-3-ghz-25-gbps-docsis/download |publisher=SCTE•ISBE |access-date=2 March 2024}}</ref><ref>{{cite web | url=https://broadbandlibrary.com/complexity-is-complex/ | title=Complexity is Complex &#124; | date=November 18, 2019 }}</ref> Changes in the frequency range used for upstream signals have been proposed: a mid split which uses frequencies from 5 to 85&nbsp;MHz for the upstream, a high split which uses a range from 5 to 205&nbsp;MHz, and an ultra high split with several options that allow for ranges of up to 5 to 684&nbsp;MHz.<ref name="Paper - Network Capacity Options on">{{cite web | url=https://www.nctatechnicalpapers.com/Paper/2022/FTF22_WLINE06_Sundaresan_3895 | title=Paper - Network Capacity Options on the Path to 10G - NCTA Technical Papers }}</ref> Full duplex (FDX) DOCSIS allows upstream and downstream signals to simultaneously occupy a single frequency range without time division multiplexing.<ref>{{cite web | url=https://www.nctatechnicalpapers.com/Paper/2018/2018-fdx-d3-1-capacity-scenarios | title=Paper - FDX & D3.1 Capacity Scenarios - NCTA Technical Papers }}</ref> Cable operators have been gradually shifting to FTTP networks using PON ([[Passive Optical Network]]s).<ref>{{Cite web |last=Baumgartner |first=Jeff |date=2024-03-07 |title=The 'cable' fade-out continues |url=https://www.lightreading.com/cable-technology/the-cable-fade-out-continues#close-modal |website=www.lightreading.com}}</ref><ref>{{Cite web |last=Brown |first=Karen |date=2021-06-18 |title=Cable players are taking many paths to PON |url=https://www.lightreading.com/cable-technology/cable-players-are-taking-many-paths-to-pon |website=www.lightreading.com}}</ref><ref>{{cite web | url=https://techblog.comsoc.org/2023/11/21/omdia-cable-network-operators-deploy-pons/ | title=Omdia: Cable network operators deploy PONs – Technology Blog }}</ref>

==Transport over HFC network==
By using [[frequency-division multiplexing]], a HFC network may carry a variety of services, including analog TV, digital TV ([[SDTV]] or [[HDTV]]), [[video on demand]], telephony, and internet traffic. Services on these systems are carried on RF signals in the 5&nbsp;MHz to 1000&nbsp;MHz frequency band.

The HFC network is typically operated bi-directionally, meaning that signals are carried in both directions on the same network from the headend/hub office to the home, and from the home to the headend/hub office. The ''forward-path'' or ''[[downstream (networking)|downstream]]'' signals carry information from the headend/hub office to the home, such as video content, voice and Internet traffic. The very first HFC networks, and very old unupgraded HFC networks, are only one-way systems. Equipment for one-way systems may use [[Plain old telephone service|POTS]] or radio networks to communicate to the headend.<ref>{{Cite book|url=https://books.google.com/books?id=e3rAmuQSUXkC&dq=hfc+network+one+way&pg=PA188|title=Multimedia Networking: Technology, Management and Applications: Technology, Management and Applications|first=Syed, Mahbubur|last=Rahman|date=July 1, 2001|publisher=Idea Group Inc (IGI)|isbn=978-1-59140-005-9 |via=Google Books}}</ref> HFC makes two-way communication over a cable network practical because it reduces the number of amplifiers in these networks.<ref name="auto6"/>

The ''return-path'' or ''[[upstream (networking)|upstream]]'' signals carry information from the home to the headend/hub office, such as control signals to order a movie or internet upstream traffic. The forward-path and the return-path are carried over the same coaxial cable in both directions between the optical node and the home.

To prevent interference of signals, the frequency band is divided into two sections. In countries that have traditionally used [[NTSC-M|NTSC System M]], the sections are 52–1000&nbsp;MHz for forward-path signals, and 5–42&nbsp;MHz for return-path signals.<ref name="Paper - Network Capacity Options on"/> Other countries use different band sizes, but are similar in that there is much more bandwidth for downstream communication than for upstream communication.

Traditionally, since video content was sent only to the home, the HFC network was structured to be ''asymmetrical'': one direction has much more data-carrying capacity than the other direction. The return path was originally used for only some control signals to order movies, etc., which required very little bandwidth. As additional services have been added to the HFC network, such as [[Internet access]] and telephony, the return path is being utilised more.

=== Multiple-system operators ===
{{see also|Broadcast television system}}
[[Multiple-system operator|Multi-system operator]]s (MSOs) developed methods of sending the various services over RF signals on the fiber optic and coaxial copper cables. The original method to transport video over the HFC network and, still the most widely used method, is by modulation of standard analog TV channels which is similar to the method used for transmission of over-the-air broadcast.

One analog TV channel occupies a 6-MHz-wide frequency band in [[NTSC]]-based systems, or an 8-MHz-wide frequency band in PAL or SECAM-based systems. Each channel is centred on a specific frequency carrier so that there is no interference with adjacent or harmonic channels. To be able to view a digitally modulated channel, home, or [[customer-premises equipment]] (CPE), e.g. digital televisions, computers, or [[set-top box]]es, are required to convert the RF signals to signals that are compatible with display devices such as analog televisions or computer monitors. The US Federal Communications Commission (FCC) has ruled that consumers can obtain a cable card from their local MSO to authorize viewing digital channels.

By using digital video compression techniques, multiple standard and high-definition TV channels can be carried on one 6 or 8&nbsp;MHz frequency carrier, thus increasing the channel carrying capacity of the HFC network by 10 times or more versus an all-analog network.

==Comparison to competing network technologies==
[[Digital subscriber line]] (DSL) is a technology used by traditional telephone companies to deliver advanced services (high-speed data and sometimes video) over twisted pair copper telephone wires. It typically has lower data carrying capacity than HFC networks and data speeds can be range-limited by line lengths and quality.

[[Satellite television]] competes very well with HFC networks in delivering broadcast video services. [[satellite Internet access|Interactive satellite systems]] are less competitive in urban environments because of their large [[round-trip delay time]]s, but are attractive in rural areas and other environments with insufficient or no deployed terrestrial infrastructure.

Analogous to HFC, [[fiber in the loop]] (FITL) technology is used by telephone [[local exchange carrier]]s to provide advanced services to telephone customers over the [[plain old telephone service]] (POTS) [[local loop]].

In the 2000s, telecom companies started significant deployments of [[fiber to the x]] (FTTX) such as [[passive optical network]] solutions to deliver video, data and voice to compete with cable operators. These can be costly to deploy but they can provide large bandwidth capacity especially for data services.

==Gallery==
Inside a headend:
<gallery>
File:Disjoncteurs, onduleur, batteries CityPlay Amiens.jpg|-48V supply systems and UPS system: many telecommunications devices at ISPs and headends are powered by -48V DC power. 
File:Baies de brassage optique CityPlay Amiens.jpg|Fiber entrance cabinet with numerous trays on the sides, the cabinet connects the headend to fiber optic cables connected to optical nodes outdoors, equipment and cables outdoors are called the outside plant 
File:Cassette fibre optique CityPlay Amiens.jpg|Inside one of the trays with fiber splices inside the tray and connectors folded out
File:Routeurs de cœur de réseau CityPlay Amiens.jpg|Core router for internet access to the CMTS
File:Amplication du signal satellite CityPlay Amiens.jpg|Satellite TV signal amplification to prepare it for reception
File:Équipements télévision divers CityPlay Amiens (4).jpg|Satellite TV reception equipment, on the right and center there are DVB [[Asynchronous serial interface]] multiplexers to package several channels in one DVB Asynchronous serial interface stream to prepare it for distribution via the HFC network, just before the edge QAMs<ref>https://www.diemstore.eu/media/art/attach/Rtm-3300.pdf</ref>
File:Digital Content Manager D9900 CityPlay Amiens.jpg|TV encryption and DRM equipment (DCM, Digital Content Manager) can be used for IPTV transmission to users<ref>Cisco DCM Series D9900 Digital Content Manager, Cisco purchased Scientific Atlanta</ref>
File:Digital Content Manager D9900 CityPlay Amiens (nouvelle génération).jpg|Another Digital Content Manager (Top), Edge QAM (middle)
File:Streamer Anevia CityPlay Amiens.jpg|Satellite TV reception device (ip streamer) with Conditional Access Cards inserted to receive encrypted satellite TV which is then turned into MPEG IP streams via Ethernet<ref>Anevia Flamingo 660 User Manual</ref> 
File:Baies NagraVision CityPlay Amiens.jpg|Unused analog DRM, Conditional access system for cable TV([[Nagravision]])
File:Équipements télévision divers CityPlay Amiens.jpg|Analog TV modulators and up-converters for insertion into the HFC network 
File:Baies_Viaccess_et_serveur_Compaq_CityPlay_Amiens.jpg |In the bottom half of the image: [[Viaccess]] encryption and conditional access system with 3 black rackmount servers and 2 silver devices which are card readers
</gallery>

==See also==
{{Div col|colwidth=30em}}
* [[Access network]]
* [[Backbone network]]
* [[Cable modem]]
* [[Cable modem termination system|Cable modem termination system (CMTS)]]
* [[DOCSIS]]
* [[FTTLA]]
* [[Multimedia over Coax Alliance]]
* [[National Cable & Telecommunications Association]] (NCTA – US)
* [[Network service provider]]
* [[Radio frequency over glass]] (RFoG)
* [[Quadrature amplitude modulation]]
* [[MPEG-2]]
* [[Multichannel multipoint distribution service]]
* [[SCTE|Society of Cable Television Engineers]] (SCTE – US)
{{div col end}}

==References==
{{Reflist}}

== External links ==
* [https://web.archive.org/web/20150909225623/http://services.eng.uts.edu.au/~kumbes/ra/Access-Networks/hfc/cnethfc.htm Information on HFC networks in Australia]
{{telecommunications}}

[[Category:Broadband]]
[[Category:Fiber-optic communications]]
[[Category:Digital cable]]