With an ever increasing number of network installs involving fibre optics and fibre optic testing there is an important difference between Tier 1 and Tier 2 fibre optic testing to be considered. With all testing standard certificates being done at tier 1 below will help outline the difference between the two standards and why you might ask for this type of test
Tier 1 fibre optic testing
Tier 1 is testing a fibre with a piece of equipment known as OLTS (Optical Loss Test Set). The OLTS tests the total amount of light loss in a fibre. A console is connected at one end which produces and transmits a specific wavelength depending on which type of fibre is in place. For more information on fibre optic cable types read our page linked. A power meter remote is then connected to the opposite end of the fibre. The remote measures the wavelength produced by the console and determines the total power loss. An OLTS displays the results like the image below.
Tier 2 fibre optic testing
Tier 2 is testing a fibre with a piece of equipment called OTDR (Optical Time Delay Reflectometer). The OTDR test finds and characterises any reflective and non reflective events in a fibre. This test pinpoints the locations of any faults or breaks in a fibre but also any loss in any connectors or joins in an install. The OTDR console is connected to one end and uses a special pulsed laser diode to transmit high power light pulses. As the pulses travel down the fibre and high gain light detectors measure any light reflected from each pulse. When a pulse of light meets a connector, splices, breaks, cracks and sharp bends it reflects due to the change in the refractive index. These are called Fresnel reflections and are also measured in dB. An OTDR displays the results like the image below.
Conclusion
All fibre optic installs should be tested at Tier 1 certificate standard as described by Telecommunications Industry Association (TIA). There is an increasing demand for Tier 2 certification standards as the margins for loss are stricter on modern fibre technologies. As OLTS and OTDR are different tests, ( OLTS tests total loss / OTDR tests loss on connectors, splice quality and breaks. These tests serve different purposes but they perform a complementary result rather than a mutually different role this can only benefit any fibre install.
