When your fiber network encounters an unexpected performance issue, often the first instinct is to replace a connector, jumper, or a trunk in a haphazard way to restore service. While this may initially seem to be the fastest method, oftentimes it may be more costly and potentially more disruptive. Some may compare this to an inexperienced auto mechanic randomly installing parts in your car in an attempt to resolve a concern without proper diagnostic tools, all at your added expense. Like the auto analogy, when it comes to fiber networks, having the right tools and knowledge of what to look for can quickly identify the issue and allow you to properly correct or address the problem the right way, likely with less material and labor costs.
There are many brands and types of equipment on the market to perform this type of diagnosis, but when the problem occurs, scrambling to research what ...
Optical time domain reflectometers (OTDRs) are critical instruments for evaluating optical fiber spans. Like any technology, they are not infallible. As the term ‘reflectometer’ implies, OTDRs work by analyzing optical signals which are reflected (and scattered) back to them. Some people call them “cable radar” because they analyze a reflected signal and not the transmitted signal. Due to this, OTDRs will sometimes generate measurement “artifacts”. One such artifact is a secondary reflection, or an “echo” - often referred to as a GHOST! After reading this article, you won’t be afraid of no ghosts!
Ghosts in the noise
The most common ghosts occur on short spans with a highly reflective open fiber end. In this case, the end of the fiber at distance L1 will generate a high-powered reflection that will arrive back at the OTDR connector. Much of it is received ...
The OTDR is one of the most powerful tools you will purchase to support your fiber network. This article discusses one key but sometimes confusing OTDR specification, Dynamic Range.
The informal definition of Dynamic Range is “how far can my OTDR see?” There are at least two formal definitions of Dynamic Range, the Telcordia definition (the most widely accepted and specified), and IEC definition. Each of these specify the amount of (one way) fiber loss from the initial backscatter (fiber) signature to a given Signal to Noise Ratio (SNR) level on the OTDR trace.
OTDR Dynamic Range Specification (SNR Limit)
IEC 98% Telcordia 50%
The IEC range wil ...