2016 / Did You Know....

That fiber backhaul links need to be characterized before upgrades? / October-November 2016

As electronics push the upper limits of bandwidth capacity, 100Gb/s to multi Terabit, optical fibers need to be characterized. Testing for polarization and chromatic dispersion as well as ORL and reflection testing will ensure that the fiber will handle the network speeds of tomorrow.  Understanding how the test and transmission equipment work and what the characterization information reveals will help ensure future upgrades go smoothly.

The most accurate method to test multimode fiber? / August-September 2016

For high-speed applications where loss budgets are likely to be tight, achieving reliable loss test results through the proper test equipment setup is critical. Your specific application, multimode fiber, test equipment, and launch conditions will dictate proper optical loss testing techniques. The best results will come from testing with light sources that closely match your fiber optic transmitter. The most accurate test method today for high-speed multimode fiber testing uses an encircled flux (EF) compliant light source, a calibrated power meter, and quality test reference cords (TRC). For light sources that are not EF compliant, you can use an EF modal launch controlling cord in place of the TRC. For older LED systems, mandrel wrapping the TRC on the optical source side is still widely accepted. However, this method doesn’t address the accuracy and repeatability requirements of high speed (10 Gb/s+) systems. Whenever possible, using the one-jumper reference method to test optical loss in multimode links will also help to produce the most accurate and repeatable results.

And – regardless which technique you use – always inspect and clean your test cords and keep them capped when not in use.

You can use your smartphone as part of your fiber optic testing solution? / July 2016

Many companies and equipment manufacturers are integrating their test platforms with cloud solutions. The latest generations of test equipment interface with an app on your mobile device as well as view and store test results and create projects in a cloud-based system. Some of these allow you to see your assigned testing project and parameters, view and save test data as it is collected, and recall and share results via email, text, or mobile cloud applications. By syncing results data to the cloud, you no longer have to save it to a USB drive and risk the chance of lost test data or managers waiting for the information. We recently saw a great demo of a new system from AFL and have seen EXFO, Viavi, Fluke and other test equipment manufacturers continue to offer various levels of support via mobile devices and cloud solutions.

You can improve the accuracy of OTDR tests? / June 2016

A technician who understands the four basic settings on an OTDR — pulsewidth, range, index of refraction (IOR), and wavelength — can get more accurate and useful results than when using the OTDR in automatic mode. In auto mode, the OTDR software does not always determine the settings needed for shortest pulsewidth, resulting in the shortest dead zone and the best resolutions. In addition, the automatic feature sometimes chooses a range that is too long, resulting in an image that does not utilize the full width of the OTDR screen.  In addition, IOR and wavelength are not automatic feature options and must be input by the technician.  IOR is crucial for accurate distance measurements, while testing at multiple wavelengths reveals micro and macrobending issues.

For accurate optical loss test results, proper referencing or zeroing of the equipment is critical? / May 2016

The best practice is to follow is the one jumper reference method. This test reference cord is cleaned and mated between the optical source and power meter. The measurement is reset or "zeroed out" on the power meter so it displays “0 dB”. The test cord is then detached from the power meter side only and not from the light source. The reference cable is then plugged into one end of the network while still attached to the light source. An additional clean test reference cord is then plugged into the far end of the network between the patch panel and the power meter. Once this is completed, the total loss in the link will be displayed on the power meter in dB.

Fiber optic cables have an enemy? / March-April 2016

Fiber is immune to many things that would impact a copper based system, such as electromagnetic interference (EMI) and radio-frequency interference (RFI) – but it’s not immune to Mother Nature! The main enemy of optical fiber is water. While water will not create a short circuit as it does with copper, any water introduced into a cable can cause several problems. Once inside the cable, swelling of materials and freezing can add stresses to the fiber, causing microbends and adding attenuation to a link. Extended exposure to water can cause hydrogen ions to be absorbed by the glass itself, creating added loss at certain transmission wavelengths (often referred to as the ‘water peak’) over time. Outside plant (OSP) cables should be used in outdoor environments as they are made from more water resistant materials and have moisture blocking materials inside to prevent water ingress.

There is more fiber in more homes? / January-February 2016

The increased pace of FTTH deployments that began in 2011 is still going strong. According to RVA, LLC, 2015 marked the second biggest year of FTTH expansion in the technology’s history. Three million new homes were passed, a growth of 13%.  Currently, 26 million homes have been passed and marketed in the United States, which now boasts nearly 20% of the world’s fiber connections.

Did You Know 2015 archive