Decades of advancements have the cabling industry poised to support more than computing functions for the long-term.
In 1993 the debut issue of Cabling Installation & Maintenance magazine was published. With a front cover portraying an installer punching down wires to a 110 block, that first issue included articles addressing angle-cleaved optical fibers, misconceptions about capability differences between shielded and unshielded twisted-pair cabling systems, selecting the most appropriate optical time-domain reflectometer (OTDR) for system troubleshooting, and a connector interface (the SC) gaining acceptance within the Telecommunications Industry Association’s (TIA) cabling-standards development committee as the fiber connector of record for premises-cablingapplications.
Other articles published that year described technical issues like Category 5 cabling’s ability to support 10-Mbit/sec Ethernet applications, harmonization of standards, planning a cabling system so it has the ability to support future applications, migrating to a fiber-opticinfrastructure.
This article, written to commemorate Cabling Installation & Maintenance’s 25th anniversary of publication, will summarize technological developments made in several spheres of the cabling industry—technical achievements, product evolution, and standards development. The article also will look into the near future, to examine how decades of advancement position today’s physical-layer cabling infrastructure to support the developing needs of users around the world.
We at the magazine are not quite egotistical enough to believe that our debut in the industry represents any type of significant historical marker. By the time the magazine came into existence in 1993, Category 3, 4, and 5 cable was standardized. The IEEE’s 802.3u standard, specifying 100Base-TX and 100Base-FX Fast Ethernet were still a couple years down the road. And 62.5/125-micron fiber was the popular choice nearly everywhere, because its numerical aperture was greater than that of smaller-core 50/125-micron’s, enabling it to receive more signals from the light-emitting-diode-based optical transmitters in use at the time. Let’s take a look at how technologies have evolved since then.
While Token Ring and Asynchronous Transfer Mode (ATM) were commonly deployed transmission schemes 25 years ago, Ethernet gained and never lost a stronghold on enterprise networking. Today it also is commonly deployed in data centers’ local area network (LAN) environments, though not in storage area network (SAN) spaces. Ethernet specifications are developed by the Institute of Electrical and Electronics Engineers (IEEE) 802.3 Working Group.
The trade association The Ethernet Alliance created and continues to update the Ethernet Roadmap, which charts the course of Ethernet speeds past, present and future. The Alliance’s 2016 version of the roadmap illustrates the time points at which Ethernet specifications were completed, as well as anticipated completion dates of future specifications. 10-Mbit/sec iterations 10Base-T (twisted-pair; 1990) and 10Base-F (fiber-optic; 1993) were followed by 1995’s 100Base-TX, 100Base-TR, and 100Base-FX Fast Ethernet. 1998 ushered in gigabit speeds, with 1000Base-X over fiber-optic cabling; 1000Base-T, gig speed over twisted-pair, followed in 1999.
Several flavors of 10-Gbit Ethernet emerged in 2002 via the IEEE’s 802.3ae standard, which specified 10GBase-SR, -LR, -ER, -SW, -LW, and -EW. 10-Gig copper versions followed in 2004 (10GBase-CX4 over twinax) and 2006 (10GBase-T over twisted-pair). In 2010, 802.3ba specified 40- and 100-Gbit/sec Ethernet over various constructions of singlemode and multimode fiber, as well as copper-based backplanes. The 802.3bm specification published in 2015 also was a 40/100-Gbit/sec specification, noteworthy in our industry because it defined physical layer specifications and management parameters for 40-Gbit/sec operation over singlemode fiber and 100-Gbit/sec operation over multimode fiber.
2016’s 802.3bq specified 25/40GBase-T; and in 2017, 802.3bs defined 200-Gbit Ethernet over singlemode, and 400-Gbit Ethernet over singlemode and multimode fiber.
On the horizon, according to the Ethernet Alliance Roadmap, are specifications that will define 800-Gbit as well as 1.6- 3.2-, and 6.4-Terabit/secondtransmission.
The above-referenced standards are not a comprehensive set of the documents produced within the IEEE’s 802.3 Working Group, but rather represent certain milestones for the increasing speeds of Ethernet-basedtransmission.
The fundamental components that enable data transmission are cable and connectivity. As the aforementioned increases in transmission speed have come to fruition, cables and connectors have had to evolve accordingly. It’s worth noting that when the IEEE 802.3 Working Group develops a specification, one of its objectives is for the Ethernet application to be supported by the installed base of cabling infrastructure. When possible, 802.3 defines parameters that enable signal transmission over existing cabling. There are times, however, when the IEEE works closely with the TIA, as the IEEE’s development of a new transmission-speed specification progresses in parallel with the TIA’s development of a new cabling-performancespecification.
1000Base-T is an example of this dynamic. The IEEE’s intention was for 1000Base-T to operate over existing Category 5 cabling. And 1000Base-T could operate over some of that installed base. But as the IEEE developed 1000Base-T and a cabling system’s electrical-performance requirements to support 1000Base-T became known, it was clear that only some Category 5 cabling systems would successfully support it. Marginally produced or installed Category 5 could not perform at the level required for 1000Base-T support. The TIA published Telecommunications Systems Bulletin TSB-95, titled Additional Transmission Performance Guidelines for 4-Pair 100 Ohm Category 5 Cabling. That document added the performance parameters return loss and equal-level far-end crosstalk (ELFEXT) loss.
But not all Category 5 cabling met the performance requirements to support Gigabit Ethernet. The TIA developed the Category 5E specifications, with a specific purpose of ensuring that a compliant Category 5E cabling system would support Gigabit Ethernet.
That pattern repeated itself when the IEEE produced the 10GBase-T specifications, with the objective of operating the 10-Gig scheme over Category 6 cabling. The TIA’s TSB-155, and later TSB-155-A documents served a similar purpose to what TSB-95 had served previously. Meanwhile, the TIA developed Category 6A cabling specifications; a standard-compliant Category 6A system will support 10GBase-T.
Today, both Category 8 specifications and 25/40GBase-T specifications exist. Though Category 8 cabling systems do not yet proliferate and there is no 25/40GBase-T network equipment currently available, the hand-in-glove fit of Category 8 and 25/40GBase-T promises there will be no need for a TSB-155-type document to assess the installed base of Category 6A.
From the standpoint of cable construction, shielding became more and more a part of the picture as more demands were placed in twisted-pair cabling. 10GBase-T’s alien-crosstalk potential caused many to take a close look at the F/UTP cable construction, which includes an overall foil within the cable jacket that surrounds all four pairs. And Category 8 is a fully shielded cable, typically taking the form of S/FTP, a construction in which each twisted pair is shielded and all four pairs are surrounded by a braid-style metallic element.
Multimode fiber-optic cable has taken an equally interesting path to its current performance level. Development of 1000Base-X fiber-based Gigabit Ethernet required the use of laser-based rather than LED-based signal sources to achieve such high speeds. In laser-based systems, with highly concentrated pulses, smaller-core 50-micron fiber is a more effective medium than 62.5-micron at supporting gigabit-speed signals over long distances. So 50-micron became the preferred optical fiber for speeds of 1 Gigabit and beyond.
Furthermore, the 50-micron fiber that had been manufactured prior to the development of 1000Base-X did not possess ideal information-carrying characteristics for such high speeds. Optical-fiber manufacturers developed 50-micron fiber specifically designed for Gigabit Ethernet transmission, and the new fiber type was called “laser-optimized.” The international cabling-standards development body International Organization for Standardization/International Electrotechnical Commission (ISO/IEC) developed “OM” (optical multimode) numerical classifications to identify multimode fiber performance capabilities. OM1 fiber has a 62.5-micron core and a 200 MHz·km modal bandwidth at 850 nm. OM2 fiber has a 50-micron core and a 500 MHz·km modal bandwidth at 850 nm, while OM3, also 50-micron, has a 1500 MHz·km modal bandwidth at 850 nm. While OM2 and OM3 both support 1000Base-SX to 550 meters, OM3 provides 300-meter support for 10-Gbit/sec 10GBase-SR, while OM2 supports the same 10GBase-SR to 82 meters.
OM4 optical fiber’s 3500 MHz·km bandwidth enables it to support 10GBase-SR to 400 meters. And the latest development in multimode optical fiber is OM5, which also has a 3500 MHz·km bandwidth at 850 nm, but unlike its multimode predecessors, also supports high-speed transmission in other short-wavelength operating windows. As such, OM5 enables short-wave-division multiplex operation over multimode fiber. SWDM componentry operates over wavelengths approximately between 850 and 940 nm. SWDM allows a high-speed signal to be divided and sent over duplex rather than parallel fibers. For example, a 40-Gbit/sec signal can be sent over 4 separate paths, each supporting 10 Gbits, on a single fiber.
One of OM5/SWDM’s value propositions is that it allows duplex rather than parallel-optic transmission, which brings the topic of connectivity into theconversation.
Over the past decade-plus, multifiber push-on (MPO) style optical connectivity has skyrocketed in use, thanks in large part to the high-speed, high-density, parallel-optic networking systems deployed in data centers. Many data center networks, including preterminated fiber-optic systems, employ MPO-based trunks in combination with LC-based breakouts.
The LC connector has its own story in the history of the cabling industry. In the late 1990s the TIA’s cabling-standards-development group wished to specify a preferred fiber connector interface to succeed the SC. A signficant consideration was density; the ability to fit more connections into a given footprint was a primary objective. Several manufacturers put forth connector designs that met the density objective, but ultimately the standards-development group did not specify one preferred interface. Rather, it opted to let the market decide. In 2018 few would dispute that the market decided on the LC, evidenced by its near ubiquity within the installed base.
Connectivity for twisted-pair copper cabling may have had a less-storied history than its fiber counterparts, but things have gotten interesting recently. The 8-position 8-contact interface (commonly but technically incorrectly called the RJ45) has been deployed globally, and has supported successive generations of Category cabling.
That changed to some extent when the ISO/IEC (but not the TIA) developed Class F/Category 7 and Class FA/Category 7A specifications. With frequencies crossing the 1-GHz mark, Class FA/Category 7A adopted non-RJ interfaces, some of which were RJ-compatible and some of which were not. When the TIA developed Category 8, it stuck with the RJ connector style. ISO/IEC’s Class I/Category 8.1 and Class II/Category 8.2 cabling specifications recognize RJ and non-RJ interfaces.
Another interesting recent turn related to twisted-pair plugs is the emergence of versions that can be terminated in the field. Begun as a rogue practice with modular plugs that were not up to the task, field termination in this style has been standardized as the modular plug terminated link (MPTL). Today this termination style is used to connect devices like wireless access points and surveillance cameras, but it also holds promise to be the default method by which Internet of Things (IoT) and intelligent-building applications are connected to the IP network.
In most cases, an installed cabling link will be tested to ensure it meets the ultimate user’s needs and expectations. In recent years those users have begun to rely on twisted-pair cabling to support more than just the transfer of bits and bytes. From video streams to power transmission, the applications that now rely on twisted-pair have made never-before-measured electrical characteristics critical. Accordingly, the equipment that tests installed cabling links must provide these services in order to be full-function tools.
Another development that has improved day-to-day operations for test technicians is the ability of many testers to upload test results to a cloud-based storage and management platform.
Housing and protecting
Within telecom rooms and other spaces in which cabling is terminated or connected, equipment like racks and enclosures house and sometimes protect the networking and cabling equipment. Today, cabling is deployed in more places than ever before, from hyperscale data centers to oil rigs, and all kinds of computing environments in between.
In many of these cases, network owners are turning to enclosures designed and manufactured for the environments in which they are placed. In some cases, the enclosures provide thermal management. In others, they protect against natural elements or the rigors of a manufacturing facility.
In 2018, the selection of racks or enclosures for a network and cabling installation can require more research and forethought than ever before.
So is the past prologue? Has the development of technologies and products, and the evolution of standard specifications, laid the groundwork for what is ahead of the cabling industry over the next several years?
One could make a convincing argument that the cabling technology exists to support expanding applications well into the future. Some argue that singlemode fiber is the way of the future for high-speed data center networking. It may be. On an entirely different side of the industry, single-pair cabling and single-pair Ethernet are shaping up to enable the connected industrial plant.
Of course, nobody knows what the next 25 years will hold; nobody knows for sure what the next 5 will hold. But if the past few decades are an indication, professionals from all spheres of the cabling industry will rise to the occasion of meeting tomorrow’s needs.