By Yumi Kato, Product Marketing Manager, and Ken Fridley, System Engineer, of Sunrise Telecom
CedMagazine.com - July 2009
Completing thorough testing and performance verification is essential
Most new developments, also known as greenfields, benefit from the use of new fiber-to-the-premises plant. Alternatively, the service provider may choose to utilize existing copper plant in a fiber-to-the-node configuration. Whatever form the outside plant (OSP) takes, most greenfields will have some form of structured cabling that may be terminated at a centralized location – called a smart panel. This can result in fast and efficient installations; but while seemingly ideal, service providers and technicians should not assume that everything will work just because it’s new.
Before any inside installation begins, technicians must verify that the OSP was provisioned properly. For FTTP installations, that means installing and checking the optical network termination unit. The ONT terminates and converts optical signals into various electrical formats, such as Ethernet, HPNA or MoCA. Each interface should be checked for valid operation before moving indoors.
For FTTN installations, installers should verify that an acceptable signal exists at the network interface device (NID). Using test equipment, the technician can plug into each port to verify services. If TDM or VoIP voice services are provisioned, the technician should also verify connectivity by placing/receiving a call directly from the ONT/NID. Both types of installations require proper grounding for safe operation. Once verified, the technician is ready to move inside the home.
Inside, technicians must determine and verify that the cable installation was done properly by the installation company. A good installation company will ensure that every cable is properly terminated, labeled and ready for activation. Some installation companies pay by the wire, which tends to motivate their installers to finish as quickly as possible – the more wire run in a day, the more money made. Wiring may also be installed by a contractor with only a basic understanding of telecommunications services and technology. Consequently, the wiring may have to be redone or corrected, significantly increasing installation time and costs. Working with developers from the beginning usually results in a better installation.
Most greenfield applications will have at least one unshielded twisted pair (UTP) and/or coaxial wire run per room, but sometimes there may be more. Technicians may find a home that has eight, 10 or 12 jacks scattered throughout the house, when, for example, only four may be needed – one per set-top box in each of the four rooms is typically all that’s necessary.
During installation, it’s normal to connect only the jacks that will be used, and to disconnect any that aren’t needed. This helps prevent vacant cable runs from acting as an antenna and contributing noise ingress and other disturbances. It pays to make sure unused jacks are in fact disconnected.
Better test platforms include cable identification devices, called dongles, which plug directly into the outlet and are numbered for easy identification. Once set up, technicians go to the main termination location and connect their test set to each individual cable run, one at a time. The test set reads out the number and identifies the room where each cable terminates. Alternatively, in a multiple-dwelling unit, the technician may use a tone generator that attaches at the customer’s residence and a receiver wand at the main feed. The technician simply waves the receiver wand across the termination point, listens to the tone and identifies which feed belongs to their customer.
The next step is service verification. This requires end-to-end tests to measure for excessive signal loss and proper termination. Excessive loss can result from poor-quality cable, improper or loose terminations, or excessive splitters. If unshielded twisted pair wiring is used, it must be at least Cat-5 or greater quality for Ethernet applications. Technicians must verify that the termination at both ends conforms to only one cabling standard, either TIA-568-A or TIA-568-B, as each have different RJ45 pinouts. Mixing the two standards on each end of the cable will render that run unusable.
For coax qualification, it is important to conduct a coax cable loss test to ensure the cable supports the frequency range required by the digital signal to be transmitted. For example, HPNA can transmit from 4 to 28 MHz. At these frequencies, the average expected signal loss over RG-6 and RG-59 coaxial cable is about 1 to 1.2 decibels (dB) per 100 feet of coaxial cable. Most average-size houses have wire runs this length or shorter. Cable loss testing sends a set of frequencies from a source transmitter at a known and repeatable level. The test set acts as a receiver and calculates the difference between the power transmitted and that received by the test set.
Loss of 3 dB or more indicates three possible problems that, if not rectified, can cause service issues: a bad F-connector, a splitter exists or a bad cable. Trouble associated with F-connectors is usually due to improper installation. Once corrected or replaced, a loss of 3 dB or more indicates that there may be a hidden splitter. A single splitter of acceptable quality may be left in place for wire runs going to set-top boxes. If the signal loss is due to impairment, the coaxial cable needs to be replaced. Damaged cable is extremely rare in a greenfield environment, but it can happen.
The primary cause of cable loss is usually at the termination points. During cable qualification, technicians should confirm that F-connectors are compression-type, barrel connectors are connected securely, and all wiring is properly terminated and tightened. Barrel splices exposed to the elements should be insulated with shrink tube or electrical tape to prevent water ingress. The rule with F-connectors and barrels is, “When in doubt, swap them out.”
After cable qualification, technicians should perform a final, all-encompassing test to verify the quality of the service performance. Service verification tests can find imperfections that, if left unrepaired, can result in service calls. Most greenfield installations will use Ethernet, making service verification straightforward. For HPNA and MoCA installations, point-to-point and whole-home testing verifies that each cable run and each device is working at peak performance. Technicians should verify that the cables and IPTV work and run standard tests that send packets to every node on the home network. This verifies maximum bit rate, signal-to-noise ratio, received errors, etc., and checks real-life performance.
While technicians – and leadership – may expect faster, simpler installations in greenfield sites, assuming that the developer’s installation contractor delivered fully functional cable runs can lead to problems and costly truck rolls in the future. As triple-play services evolve, new and improved test systems will debut, designed to reduce or eliminate provisioning and maintenance challenges. Completing thorough testing and performance verification before turning new services over to the customer is essential. For the service provider, and even pre-wire installation contractors, an all-in-one test set lowers the total cost of ownership by eliminating the need to acquire and maintain multiple test sets for each technician. For technicians, all-in-one test sets simplify each deployment by ensuring the right tests are available for every situation they may encounter.