This paper presents recommendations for wiring homes for video, voice, and data connections from fiber-to-the-home (FTTH) Optical Network Terminals ONTs. The material generally follows the terminology and recommendations of the National Electric Code, the Telephone Industries Association (TIA), and BICSI. References to all three are presented at the end of this document.
Since local codes vary and different interpretations exist, the installer should consult his own local sources for the detailed answers to wiring issues. Different requirements usually exist outside of the United States. In the event of differences between this document and local requirements, the local requirements apply.
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These recommendations follow modern structured wiring techniques. In a structured wiring environment, no wiring is looped-through or daisy-chained from one outlet to the next. Rather, all wiring to all video, voice, and data outlets is routed from a central location, where it is interconnected. This structured wiring is also known as homerun or star wiring. It allows much higher quality of signal distribution, and much more flexibility in what the homeowner can do now and in the future.
The recommendations apply directly to new work. For existing homes, compromises are inevitable. But these guidelines will still indicate the goal to which the installer should strive
Figure 1 summarizes the suggested internal wiring using conventional data wiring techniques, following the terminology of BICSI, an organization that promotes quality inside wiring. Later we shall show a diagram that uses the coaxial cable for data applications. From the ONT in the upper left, telephone, data, and video (TV) cables go into the house. The top portion of the figure shows telephone wiring, the middle portion shows data wiring, and the lower portion shows TV wiring. It is recommended that a panel designed for structured wiring be installed in a wiring closet, basement, garage, or other suitable location, to provide protection for all wiring. Larger installations may have two panels: one for voice and data and one for video. Of course, if broadcast video is not provided, the coax portion can be eliminated. Panels for this purpose are available from a number of vendors. They may even be available in your local home improvement store.
RJ-11 outlets and plugs are used for all telephone wiring. The telephone cable exiting the ONT is known as an ADO (Auxiliary Disconnect Outlet) cable, as it goes to an ADO outlet in the panel. If there is a problem with telephone operation, the homeowner may disconnect the ADO outlet and connect a telephone at that point. If the phone works there but not at normal outlets, a problem exists with inside wiring. (Note that the ADO function also exists in most Wave7 Optic ONTs.)
Figure 1. Residential Wiring Summary, Conventional Data Cabling
Telephone wiring uses a single twisted pair for communications in both directions. A so-called hybrid in the telephone allows the single pair of wires to be used for both directions at the same time. For low noise it is essential that the two wires be electrically balanced to ground, and it is also essential that they be twisted together (preferred), or at least run close to and parallel to each other. This ensures that any interference is picked up equally on each wire, and that interference is cancelled by the balanced input to the receiver.
From the ADO, a DD (Distribution Device) cable takes the phone signal to a panel that usually consists of a series of punch-down blocks interconnected in parallel (the DD) to permit connecting more than one telephone to each line. Outputs from the DD exit the panel on outlet cables, which are routed to each telephone jack in the home. Note that wiring does not run from one jack to another. This is the old daisy-chained wiring method, which is not acceptable today.
Each CAT5 (category 5) ADO cable can carry up to four telephone lines, so there is usually no need to bring multiple cables to the panel, even to support multiple phone lines. Different parallel punch-down blocks are used for different phone lines. The recommended cable to use is CAT5 or CAT 5e cable, which perform well for both voice and data applications. CAT3 cable was formerly used and you will see it in a lot of homes, but it is not recommended for new construction.
Note that an RJ-31X connector may be installed in the input from the primary telephone line. This runs to a security system, and allows the security system to capture the phone line if needed.
Lacking other information, we assume that data wiring implies Ethernet. Ethernet transmission takes place over two twisted pair of unshielded wires. The most common cable used is CAT5, which includes four twisted pair. Only two of the pair are used for normal 10/100Base-T transmission. The two remaining pair are either unused or are used for power (Power over Ethernet, PoE). For gigbit Ethernet all four twisted pair are used. As with voice wiring, transmission is balanced with respect to ground, and it is imperative to maintain the integrity of the twist. In data transmission, the characteristic impedance of the twisted pair is important, much more so than in voice transmission.
For data wiring, a similar (to voice) methodology is used. Since there are multiple 10/100Base-T connectors on most Wave7 Optics ONTs, you will probably want to bring several runs of CAT5 (or better) cable into the home, each to its own ADO. You may want to do this even if you are only using one of the data connectors at this time, in order to allow for future expansion. If you are carrying IPTV, it is recommended to use one port for IPTV and another for data.
The ADO and DD for data cables is often wired slightly differently from telephone wiring. A key need at the panel is to permit the homeowner to add a consumer Gateway or Router, to provide a firewall, additional data outlets, in-home networking, and other services. One way to wire is to bring each ADO cable from the ONT to a punch-down block on an input ADO. Then each data outlet in the home is wired to a punch-down block on the output. Short data cables (commercially available) are used to connect the input ADO with the output ADO. The homeowner may add a Router at this point if he so chooses.
Wiring Fine Points
Figure 2 summarizes some of the key points of data and voice wiring. Data cable is always CAT5, CAT5e or CAT6 (still not common in residential work). Telephone wiring is almost always CAT5, even though older CAT3 cable may still be available. Some low voltage contractors have tried to use the same CAT5 cable for both voice and data wiring. This is strongly discouraged, as shown below. BICSI, TIA, and CEDIA all recommend against using the same cable for voice and data.
It is imperative to respect twisted pairing in both data and voice cables. Communications technology relies on the inherent radiation and pickup immunity of twisted pairs (the theory behind twisted pair is explained in reference 6).
Figure 2. Wiring Fine Points
Going Wrong with Structured Wiring
Figure 3. Proper Wiring of Cat5 Cable
We have seen problems with the structured wiring that some contractors are putting in houses. A standard Cat5 cable has four twisted pairs of wires. Only two of them are needed for normal 10/100Base-T Ethernet circuits (other forms of Ethernet require all four pair). Some contractors are using one of the remaining pair for telephone cabling. This is not recommended, but has been found to work, at least in some cases. Both BICSI and TIA recommend against this practice. The voltage on each Ethernet pair is balanced, with a minimum amplitude at the transmitter of 900 mV p-p and a maximum voltage of 2.63 V p-p at the crest of an overshoot. The receiver works with as little as 160 mV p-p. Contrast this with the ringing voltage of a telephone pair, which can be as high as 108 volts, and you see why it is not a good idea to run telephone in the same cable as Ethernet. Unfortunately some home builders are wiring both phone and Ethernet connections in the same cable, despite an abundance of wisdom that says not to do it. Laboratory tests done by the writer in 2003 indicated that it will sometimes work, but in no way can we endorse this reckless practice.
A major problem you can encounter is pair violation. It is absolutely essential that a home be wired using not just any wires in the Cat5 cable, but using the correct wires. Figure 3 (from Ref. 6) shows the proper wiring diagram for RJ-45 connectors used with Cat5 cable for Ethernet applications. There are two acceptable wiring standards, controlled by TIA specification T568. The “A” wiring standard shown on the right is called the preferred standard, but most cables today use the “B” standard shown to the left of the A standard. Either is OK, so long as you are consistent. This will ensure that one twisted pair is used for transmit and the other for receive of the Ethernet signals. If you cross the wires, then you violate the requirement to use a twisted pair for each direction. This will cause considerable radiation, and in longer runs will cause poor or no communication. The twisted pairs have a characteristic impedance of 100 ohms, but when you violate the twisted pair assignments, you put yourself in an uncontrolled impedance environment, and anything can happen.
This section addresses broadcast TV wiring, but as we’ll see below, also applies to IPTV if you are planning to use existing coax wiring for data.
By far the most common way to connect RF components such as television sets, is through use of coaxial cable (coax). Coax consists of a center conductor surrounded by a dielectric (electrically an insulator). The dielectric is surrounded by one or more shields, another conductor. Finally, an outer insulating layer is usually added. Transmission is on the center conductor of the coax, with the return being on the shield. The shield is grounded at one and usually both ends, though in some TVs the ground may be through a capacitor that effectively breaks the ground connection at low frequencies such as the power line frequency, while ensuring a good ground at RF frequencies.
Coaxial cable wiring for broadcast television is done a little differently from data and telephone wiring. It normally uses RG-6 coaxial cable. Quad shielded cable is strongly recommended over lower-cost one, two, or three shield cables. It provides better immunity against stray signal pick-up and radiation. This can be a serious problem in modern houses with lot of digital devices operating. Connectors used on each end of the cable are F connectors, available commercially from many sources. A high quality twist-on or crimp-on connector designed for the cable with which it is used is mandatory. If a crimp type connector is used, a crimping tool specifically designed for that connector must be used. Crimp tools are generally not interchangeable between connector types. More information on coaxial cable is presented below.
The coax from the ONT is routed directly to the TV or set top box (STB) if only one set is to be served. If interference is noted on the TV, it may be that the signal level is too strong. This can be fixed by adding an inline pad (attenuator) at the input of the TV or STB. Normally a 6-10 dB pad value should suffice.
Wave7 Optics provides enough signal level to serve at least four TVs in the home, with ample allowance for cable loss. The table in Figure 4 shows how long the cable run can be, based on the number of outlets served. The cable run is measured from the ONT to the farthest TV (do not include the length of coax to other TVs). If more outlets are to be served, or if longer coax runs are necessary, booster amplifiers or RG-11 cable may be used.
Figure 4. Approximate Maximum Length of TV Wiring
In order to serve multiple TVs, a high quality splitter must be used. These are available from a number of sources, but there are low-end products in the market that should not be used. You will find some correlation between the cost of the splitter and its quality, at least up to a point. Many good splitters use the word “digital” in their description. While there is nothing digital about a splitter, it has become a buzz word that a number of manufactures apply to their lines. It means very little except that the product line has been placed on the market in the last few years. Or it may mean that the manufacturer wanted to appear up-to-date. The splitter must be rated to operate to the highest frequency used in the plant, up to 1,000 MHz in some systems. Higher frequency ratings are good. However, splitters designed for satellite work may NOT work on the cable TV band due to limited lower frequency response â€“ home satellite distribution usually ranges from 950 MHz up to 1450 MHz, 2200 MHz, or higher, depending on the system. Cable TV and FTTH broadcast use 54 to 1,000 MHz.
It is acceptable to use either a single 4-way splitter, or you can use a cascade of 2-way splitters. Three-way splitters are sometimes used. Most have one port with higher signal level (lower loss) than the other two. The high signal level port may be used to feed a 2-way splitter, or it may be used to connect the longest cable run to any TV. The location of the signal splitter(s) along the coax path is unimportant so long as the maximum distance limitations are observed. If longer distances are used, it is possible that upper channels may suffer some performance degradation, though digital channels may not be damaged.
While the splitting can be located anywhere in the signal path, in the spirit of structured wiring, it is best to locate all splitting in the wiring panel, and to run coax from here to each TV or computer location (for data over coax).
A lot of codes do not address specifically the grounding of devices such as the ONT, but we strongly recommend a local ground connection from the ONT as a safety measure. We recommend following local codes for cable TV grounding. These often require bonding the ground to the same ground point as the power is bonded if feasible. Wave7 Optics has published a white paper on grounding, Grounding FTTH ONTs, Document number 990-00002
Data Over Coax
A major improvement in serving existing homes is to avoid adding new wiring for data. A number of technologies have been developed to do this. In this section, we shall discuss putting data over coaxial cable, using either of two standards that exist: MoCA or HPNA 3 (recently revised to 3.1). MoCA is a recent development that uses the frequency spectrum above that used for cable TV. HPNA 3.1 started as a technology for putting data over phone lines, but it has been expanded to cover data over coax. It uses frequencies below the broadcast band. The maximum throughput with either technology is around 90-100 Mb/s today, with faster speeds being introduced now.
Figure 5 illustrates use of data-over-coax technology, either MoCA or HPNA. A data-to-coax bridge is located within (as shown) or external to the ONT. A coaxial cable comes out of the ONT (from the Ethernet-to-coax bridge) to a splitter, shown under the ONT. The coax splitter is normally located in the panel of Figure 1. Homerun coax connects to IP and/or RF set tops, where the IP set top has a built-in or eternal RF-to-data bridge. The coax can also serve computers, using an Ethernet-to-coax bridge connected to the coax and the computer. The bridge must use the same technology (MoCA or HPNA) as used by the bridge in the ONT and elsewhere.
Both MoCA and HPNA employ the concept of a master bridge, which sets policy for the other bridges. The other units are variously known as clients or slaves. It is convenient, but not necessary, to designate the unit at the ONT to be the master. There must be one master in the network. Failure to designate a master will result in much slower data transfer than expected. Typically there will be a physical switch to designate the master.
It is possible to use data-over-coax technology to network between computers as well as to supply IPTV and Internet data. Figure 6 illustrates use of either MoCA or HPNA3 technology to transmit both data and IPTV simultaneously. It is also being used for in-home networking. One of the data connectors on the ONT is connected to the master bridge. If broadcast (RF) video is being used, with or without IPTV, then the coax output (RF connector) on the ONT is connected to a directional coupler as shown.
Figure 5. In-home Data and Broadcast Over Coax
The directional coupler is a small passive RF device shown below the master bridge. It has the property that a signal entering the “IN” port will appear at the “OUT” port slightly reduced in amplitude. The reduction in amplitude is caused by some of the signal power being coupled to the “TAP” port. The amount of power coupled to the tap port is designated by the value of the directional coupler. Directional couplers are bidirectional devices, meaning that they work equally well in both directions. In Figure 6 we show the directional coupler being used to combine a signal from the HPNA or MoCA master, with the RF signal from the ONT. The “IN” and “OUT” nomenclature is backwards for this application, but by convention, the directional coupler will be labeled as shown. When used in this application, the signal entering at the TAP will experience a loss equal to the value of the directional coupler. The signal from the ONT, which enters the “OUT” port will suffer a small loss (typically 1 dB or less) to the “IN” port, where it exits. Confused by the ins and outs?
If RF video is not being used, then the connection from the RF connector to the directional coupler is not used, and the directional coupler is not needed. The RF connector from the master bridge is connected to the RF splitter. The splitter is another passive RF device used to divide RF signals between ports. The signal enters on the input port and exits on several output ports, depending on the number of outputs on the splitter. At least this time, we are using the device in the same direction as its markings. (There are applications where the splitter is used as a combiner, and the markings are again backwards from the application.) The output at each port is lower than the input, primarily due to the conservations of energy: if the signal is being divided into several paths, then the signal on each path must be lower in amplitude than the input signal.
Figure 6. Coax Used for Both Data and IPTV
The output from each splitter port goes to some device that needs one or more of the signals on the coax. The top two ports in Figure 6 are connected to client bridges. The top bridge has an RF output going to a set top box and then to a TV. This might be an IPTV set top box receiving IPTV data from the ONT, or it might be an RF box looking for the modulated TV programs. The top bridge is also supplying data to a computer, through an Ethernet port.
The second port on the splitter is connected to a second bridge, which in turn is connected to a computer only. The computers will access data flowing from and to the ONT for Internet connection. In addition, they can use the HPNA or MoCA devices to form a network allowing the two computers to communicate with each other, as shown. For inter-bridge communication, the RF signal from each bridge flows to the RF splitter. Now ideally the splitter has infinite isolation between output ports, so no signal can flow as shown. However, in the real world, the isolation is limited, and the technology takes advantage of that limitation to allow data to flow as shown. The signal from one client to the other can also flow back to the directional coupler and be reflected at that point, or it can be reflected from the RF connector on the ONT. However, the devices are all designed to reflect as little signal as possible (we say they have a high return loss), so there may not be adequate signal reflected to allow reception of data. In the rare cases where data performance is problematical, it is possible to install special filters to reflect the signal.
Note the need for quality of service (QoS) at this point: if an IPTV session is flowing from the ONT to one or more TVs, then any data communication between the clients must take a “backseat” to the IPTV data, because IPTV cannot tolerate the delay that would ensue if the data between computers caused the IPTV data to be delayed. Both technologies have provision for such QoS.
The two lower ports of the splitter are connected to two more TVs. The first is connected to a set top box. This may be an RF set top box, in which case it is looking for RF signals on the coax. It may be an IPTV box with a built-in client. The lower TV is receiving analog (and in rare cases digital) broadcast signals from the ONT. This emphasizes the continuing advantage of analog broadcast video in the digital age: it is the only video format that does not need some sort of a set top box. Set top boxes cost the operator money, and they can be an inconvenience for the subscriber.
Other In-home Data Networking
Besides data over coax, there are other home networking solutions being used, to put data over phone lines, through the air, or over power lines. HPNA was originally designed to operate over phone lines, and equipment to do just that is available. It may be connected to one of the data ports on the ONT.
Some people are experimenting with wireless distribution in the home. While this can work well for data, the ability of wireless infrastructure to transport video reliably is not well established. The imminent 802.11n standard is intended to work with video, and pre-standard product is on the market as this is being written. Some vendors use MIMO (multiple input multiple output) technology, in which the central transmitter, which connects to an Ethernet port on the ONT, forms the RF into a beam that is steered toward each client in turn. Additional techniques may be used to combine signal from multiple antennas. Some operators have reported a degree of success with this technique.
All RF-based technologies carry certain risks, though. The perils of the radio path are such that you cannot guarantee the level of performance, though modern technology does a lot to reduce the effect of the perils. Also, security is an issue, one without a good solution. The signal may well go from a customer to a non-customer’s residence, where the non-paying person can use the facilities of the paying customer. But since anyone can put in his own wireless access point, this is not something that an operator can conveniently control.
Finally, some people are looking at distributing data over residential power lines. There are standards for doing this, and it clearly works for lower data rates. It is specified to work at video rates, but there is little data so far to indicate the efficacy of the technology.
Appendix: Information on Coaxial Cable and Connectors
A number of different types of coaxial cable (“coax”) have been and continue to be used in home wiring. The most common type today is known as the RG-6 family. Some manufactures make variations on cables and give them different names, but the “6” should be prominent in the cable designation. For example, Commscope builds cables generically referred to at “F6.” Other cables used in residential distribution include RG-59 and RG-11. All have a characteristic impedance of 75Î©, the nearly universal impedance used for video.
Figure 7 illustrates the loss per hundred feet of various types of coaxial cable. RG-6 or similar cables are the workhorse cables today for in-home wiring. We have shown two 6-type cables. One is built specifically for cable TV drop and in-home use, and the other is rated for satellite work too, up to 2500 MHz. It has slightly lower loss than the drop cable, but of course, costs more, all else being equal.
There is also RG-59 coax, which formerly was used for home wiring, and you may find it in homes wired before some time in the 1990s. It has more loss, but is of smaller diameter. It is not suitable for modern home wiring, but can be used for short jumpers, such as from a coax wall outlet to the TV (RG-6 also works for this application). We also show RG-11 coax, which is larger and somewhat harder to work, but has lower loss. It may be appropriate for coax runs longer than those shown in Figure 2.
The maximum lengths shown in Figure 2 are derived from the worst-case loss of a splitter, the output level from the Wave7 Optics ONT, the coax loss from Figure 6, and the need to reach the TV with a minimum signal level of 0 dBmV. Because the RF output level is not covered in the FTTH standards, the same lengths may not be valid using ONTs from other manufacturers. The 0 dBmV level is required by FCC Rules for cable TV operators, and is a good number to provide quality video. Falling significantly below this value when providing analog video will cause snow in the picture. Falling significantly below this value when viewing a digital signal will cause picture freezes or no picture at all. Unfortunately, with digital video transmission, there is little possibility of estimating the quality of the received signal from looking at the picture, as there is with analog. Received digital video is either as good as that transmitted, or it is not there.
Coax shielding is very important: the more the better. The best cables for wiring a home are quad shield cables. They typically have an inner bonded foil shield, with a braid over it. Then there is an unbonded foil shield, followed by a lighter braid, then the outer insulating jacket. Quad shield cable have the best shielding and are suitable for all applications, but dual shielded cables are acceptable in some situations. Quality dual shielded cables have a bonded foil shield, then a fairly dense (60% or more coverage) braided shield. Dual shield is OK for baseband video, for data over coax, and for broadcast if there are no local off-air broadcast stations. If there are local off-air stations, the chance of pickup increases, so we recommend quad shielded cable for new installations. Dual shield may work, but quad shield is better.
Figure 7. Coaxial Cable Loss Characteristics
The connector used universally for home RF TV cabling is called the “F connector.” No one seems to know what “F” stands for here, but at one time your writer considered it to be the most appropriately-named connector around. However, in recent years a number of improvements have been made to the connectors, to the point that they do a reasonably good job today. One key is that any crimp-on F connector should have a long crimp length to ensure good contact with the coax shield. You can still find connectors with short (about Â¼ inch or less) crimp rings. About the only thing good to do with such connectors is to test your aim at the trash can.
No coax is going to work well if the connectors are not put on properly at the ends of the cable. It is imperative to use a connector designed for the cable being used. If a crimp connector is used, use the proper crimping tool specified for that connector. No substitutes, please. We have seen more coax problems due to improperly applied connectors than due to all other causes combined. A properly applied F connector will be impossible to pull off the coax by hand.
Most F connectors are screw-on connectors, but there is a push-on connector that is compatible with F female connectors (the “male” or “female” of the connector is determined by the center conductor, not the shield). Use of push-on connections is convenient, but the long-term efficacy of such connections is questionable. We cannot recommend them except for short-term testing.
1. BICSI, Residential Network Cabling, ISBN 0-07-138211-9. This text is available from a number of technical booksellers.
2. Relevant TIA standards include TIA-568 and TIA-570. These and others may be obtained at http://global.ihs.com
3. Specifications on coaxial cable and connectors may be found in the Standards section of www.scte.org
4. The latest version of the National Electric Code may be obtained at www.nfpa.com or from commercial booksellers. Note that local regulatory bodies may or may not be using the latest version, which is updated every three years. Always consult local sources.
5. A good organization for in-home wiring and other consumer technology service is the Customer Electronic Design and Installation Association, http://www.cedia.net/
6. Ciciora et. al., Modern Cable Television Technology: Video, Voice, and Data Communication, San Francisco: Elsevier, 2004, ed. 2. ISBN 1-55860-828-1. This book is available from a number of booksellers.
Coaxial cable. A type of cable used for RF transmission, consisting of an outer conductor usually connected to ground at each end, and an inner conductor. The most common characteristic impedance for video work is 75 Î©. Other common impedances include 50 Î© and (rarely) 93 Î©.
A very common form of Ethernet, capable of communicating at either 10 or 100 Mb/s over two twisted pair of the four pair in Cat5 cable.
The common in-home wireless networking set of standards, also known as WiFi. A number of forms of 802.11 exist.
Category 3 cable. An older cable used for telephone communications, consisting of two twisted pair.
Category 5 cable. The most common type of cable used for data and telephone communications, consisting of four twisted pair of wires and having a characteristic impedance of 100 Î©.
A property of communications cables that relates the voltage to current ratio that exists on the cable. It is significant because the cable must be terminated by this impedance at both ends in order to permit good signal transfer.
A passive RF component used to unequally divide RF power between two paths. May also be used backwards to couple unequal amounts of power to a common path.
A screw-on RF connector used with RF cable. This is the most common RF connector in consumer electronics.
Was Home Phone Networking Alliance, now HPNA Alliance. An organization promoting the use of a data-over-coax technology which puts the data on modulated RF carriers below the TV band. Original use, and still a popular use, is data over phone lines in the home. http://www.homepna.org/
Multiple Input Multiple Output. A technology used in wireless data communications to combine signals from two or more receive antennas in order to improve communications.
Multimedia over Coax Alliance. An organization promoting the use of a date-over-coax technology which puts the data on modulated RF carriers above the TV band. http://www.mocalliance.org/
A passive RF component used to equally divide RF power among two or more paths. May also be used backwards to couple equal amounts of power from two or more paths to a common path.
A method of wiring communications cables in a home that involves bringing individual cables to a central wiring facility. Structured wiring offers much higher quality, is more versatile, and is easier to maintain than are older forms of wiring.
 This table is based on minimum output levels from Wave7 Optics’ ONTs, and a minimum received level of 0 dBmV at the TV, consistent with FCC Rules for cable television service.
 There is no agreement as to what the “RG” designation means. The author’s favorite story, which may even be true, is that RG stands for “Radio Grade,” and was a designation that emerged in the military during WW2, when coaxial cable was developed.
 47 CFR Â§76.605(a)(3)