The amount of optical fibre cabling being installed is set to grow exponentially in the coming months and years. Fluke Networks explains how
certification can help ensure quality when installing these networks.

If a job is worth doing, it is worth doing well. This is as true in the field of installing fibre networks as it is in any other situation. However, many people still try to cut corners to avoid the effort involved in doing things right, even when they know they shouldn’t.

In a building project, enormous attention is paid to good foundations. In the networking world those foundations are industry standards. Although hidden from day-to-day view, compliance with these standards is vitally important.

Network engineers and IT professionals who install fibre are generally aware that standards exist. But they are sometimes guilty of overlooking them either deliberately or because of lack of training.

Fibre network problems can arise as a result of cost-cutting through rushed work or ‘usual’ practice rather than ‘best’ practice. For example, a tight bend rather than reworking a run or a quick blast of air instead of a full surface clean. Strictly working to standards will eliminate these problems.

Not proving adherence to industry standards through formal certification of fibre networks may provide short-term, contract winning installation savings. However it will invariably cost more in future in warranty claims, rework, servicelevel agreement (SLA) compensation and customer good will.

Industry certification standards aren’t randomly created nor do they exist to fulfil a legal obligation. Standards such as the ISO/IEC and TIA regulations exist to ensure that the network end-user gets the quality of cabling and hence service delivery that they deserve.

As demands on networks rise, close enough is no longer good enough. Faults that were initially tolerated show up, sometimes long after installation. Certifying fibre installations to known standards protects both the user and installer against long term claims.

There are two groups of industry standards to ensure the reliability of installed cabling. They include generic standards, which refer to general installation rules and performance specifications. The key standards are ISO/IEC 11801:2002, ISO/ IEC 14763-3:2006 and ANSI/TIA 568-C. Additionally, network application standards such as the IEEE standard 802.3 for Ethernet or the ANSI standard for FibreChannel must be considered.

To certify networks, the test equipment used must be configured against the latest versions of each standard. Both ISO/IEC and ANSI/TIA require two types of testing to certify a fibre network, known as Basic (Tier 1) and Extended (Tier 2).

Basic testing is a line length, line loss and polarity test. Enhanced testing requires the use of an Optical Time Domain Reflectometer (OTDR) to analyse the performance of each component in the fibre loop including splices, connectors and cable. Passing a basic test alone is not enough as individual elements in the network can be failing to meet specification, meaning any further degradation during service life can take the whole network out of specification.

These tests provide confidence in the workmanship and quality of the installation. In addition, if faults arise, an engineer equipped with baseline of measurements from certification can use comparative OTDR measurements to immediately highlight points in the network requiring detailed investigation.

BEST PRACTICES FOR A FIRST CLASS FIBRE INSTALLATION

There are fundamental procedures that help an installer work to the necessary standards. Human nature dictates that if a short-cut exists, it is likely to be taken.

When installing fibre optic cabling, this is an urge that should be heartily resisted. Adherence to long-standing procedures and practices is fundamental to achieving the necessary standards of workmanship that creates successful certification of a fibre installation.

Tier 1 and Tier 2 are the levels of testing to consider. Before any testing, it is vital to establish a datum, or reference, for the loss measurement. This lets the engineer carry out a thorough and accurate job.

Setting a fixed reference point for loss is achieved by connecting a one to three metre test reference cord (TRC) between a light source and a power meter. It is important to be sure that each end-face of the TRC is spotlessly clean and undamaged. If either end is contaminated measurements will reveal higher and misleading loss figures.

To help with this critical step, an engineer can use an optical or video fibre inspection microscope to inspect and clean the TRC, letting the reference be accurately measured and set.

There is an important point here also for operator safety. Operators should not look directly into an active fibre link. Data communication light is not visible to the human eye but it can cause damage. This simple practice of setting a reference will avoid wasting time and money on avoidable fault-finding, helping to create right-first-time results.

With the reference accurately set, the engineer can proceed to Tier 1 and Tier 2 testing of the link.

Tier 1 testing is the top level of the process. It takes a measurement of the channel or permanent link. Also known as basic testing, this is a double-ended test where the output is an absolute loss measurement, which is compared to installation cabling standards and relevant channel application standards.

To carry out Tier 1 testing, the engineer needs an Optical Loss Test Set (OLTS) also called a Light Source Power Meter (LSPM). These devices enable a full test by measuring loss within a link across its entire length.

Tier 1 testing is the bedrock of a successful installation. It meets international standards for gauging acceptable loss before a specific cable installation is accepted and put into operation.

Tier 2 certification, also known as extended testing, uses OTDR. This lets engineers break down and test individual components within each fibre link. Working in this way, it is possible to build a picture of how uniform the cable attenuation is. It can highlight any individual connector insertion loss, individual splice insertion loss or any other deficiencies that could impact the performance and reliability of the installation.

By combining suitable test equipment and paying attention to up-to-date practices, the installer can be sure that each step is competed to highest level of workmanship possible. This method of ensuring quality in an installation will boost installers’ referrals, professional reputation and ensure that the organisation has a fibre network that not only does the job, but is truly fit for purpose.

Once the network is operational, there will be increased productivity through reduced service disruption and the avoidance of the hassle associated with making warranty claims and establishing SLA compensation.