Like the TIA and ISO, Fluke Networks promotes the use of the 1-cord method to set reference for fiber loss measurements. The 1-cord method is where a launch cord is attached to a light source and the other end to a power meter. A reference is then set (the power measured is defined as 0 dB). Next, the launch cord is disconnected from the power meter, but not the light source. Then the far end of the launch cord is attached to the cabling under test and a receive cord between the far end of the cabling under test and the power meter.
We’ve covered fiber insertion loss testing in depth in many blogs, so by now you should know that it is the loss of signal that happens in a channel due to the length of the cable and any connectors, splices or splitters.
And hopefully you also know that estimating your loss budget involves adding up the loss of all of these components to make sure you’re within the loss limits specified by IEEE standards for the application you plan to run.
Our industry commonly uses the term “RJ45” to refer to the modular 8-position, 8-contact (8P8C) interface deployed for Ethernet over copper twisted-pair network cabling despite it pretty much being a case of mistaken identity.
But since the RJ45 name has stuck, we thought maybe we’d take a closer look at the history of this nomenclature and why to this day, it remains the de facto interface for twisted-pair Ethernet applications.
Jacks of All Trades
Just like those who drive around long after the engine service indicator lights up on the dashboard, there are folks out there who have likely been putting off getting their tester calibrated despite the email or LinkWare™ Live notification from Fluke Networks.
You might remember that just about three years ago, the DTX CableAnalyzer™ was officially retired. Since its discontinuation, Fluke Networks has continued to offer technical support, repair and calibration for this tester that was once touted as the ultimate time saver and brought testing to a whole new level when it was introduced in 2004.
Since today’s high-speed fiber networks use 850-nm vertical-cavity surface-emitting laser (VCSELs) transceivers, some may be confused about why light emitting diode (LED) light sources are used for testing. Understanding the differences between these two sources will certainly shed some light.
A History Lesson
Adopted by TIA, the nomenclature for multimode fiber found in the ISO/IEC 11801 standard includes the prefix “OM.”
Rather than the spiritual mantra you hear in yoga class, most sources in our industry state that the acronym OM comes from “optical multimode” which seems rather obvious. But when it comes to the various nuances of each type of OM, the differences aren’t quite as obvious.
Let’s take a closer look.
Often when we hear the term “bandwidth” we think of how much data can be sent over a fiber link. But when we look at fiber specifications, we typically see a specification for modal bandwidth, or effective modal bandwidth (EMB). This key characteristic of multimode fiber refers to how much data a specific fiber can transmit at a given wavelength, and it is dependent on another characteristic—differential mode delay.
So you’ve finished your fiber cable installation and are now on to the task of certifying the cable plant using an optical loss test set (OLTS) – it’s the tool you need for Tier 1 certification and the most accurate for measuring loss to ensure application support.
Unfortunately, you find some critical fiber links that far exceed your loss budget for the application. You now need to troubleshoot those links so you can fix the problems and move on to your next job. And the faster you can locate the problems, the faster you can fix them.
While it seems we can never hammer home enough the need to properly clean and inspect fiber end-faces since contamination remains the number one cause of fiber link failures, have you ever thought about what exactly you are cleaning and inspecting?