Using fiber connections can lead to many great advantages like distance and bandwidth. Using fiber also means that you need a few more tools in your tool box.
The light from a Multi-mode (MM) or a Single-Mode (SM) optical module cannot be seen by the human eye. It’s not possible to look into the end of the optic to see if light is coming out. If fact, if you do this (look into the fiber) when there is light coming out of it you could cause serious damage to your eye.
To view the strength of the light signal you will need a light meter. The light meter will tell you how strong the light signal is, or if there is no light. Each optical receiver may have a different threshold for how strong or week the light levels can be. I suggest you read the documentation for each brand/model of optics you have so you know the light thresholds. I have worked with some that prefer a -18dbi, while others prefer a -12dbi or only a -5dbi. Each optical module (SFP/SFP+/XFP/Xenpak/DWDM/CWDM) will be different and there is no “Sweet Spot” for all vendors optics.
To prevent a good light level from being degraded you need to make sure the ends are clean and free from scratches. I have seen a scratched fiber connector degrade the light signal below the acceptable values and cause the connection to fail. Dirt or dust can also cause this same problem. You will need a fiber scope to look at the tip of the connector. To do this, you will need to have the proper connector on the fiber scope to match the connector on the fiber (ST/LC/SC-APC/SC-UPS, etc). You can then zoom in on the tip to see if there are scratches or dirt on the connector.
If the connector is scratched, throw it out and get a new one. If it’s a new jumper, ship it back where you got it and get it replaced. Unfortunately, I have had to do this too many times. If there is simply dust on the connector, you can use a fiber cleaner to clean it. A Cletop is an example of a fiber cleaning tool that works very well. It has a lint free cloth on it that does a very good job cleaning the tip of the fiber.
In a LAN environment you don’t need a lot of tools to troubleshoot your fiber.
I recommend the following items
1. Light Meter along with a connector for every type of fiber connector you have.
2. Fiber scope along with a connector for every type of fiber connector you have.
3. Fiber cleaner, I suggest the Cletop, but there are many out there to choose from.
What fiber troubleshooting tools do you have and recommend to others? Please post your specific brand and model so others can know what works and what doesn’t!!!
Below you will find a link to Flukes website with more information on these products. I suggest you find a brand you like and trust.