Never use bend insensitive multimode fiber for test reference cords. Your 850 nm reading will be pessimistic.
This article will describe the steps required to successfully certify a multimode LC/MPO Module to LC/MPO Module fiber link in accordance with ANSI/TIA-568-C using the DTX-MFM2 fiber adapters. ANSI/TIA-568-C requires the user to follow Method B (also known as 1 Jumper) to avoid negative loss readings.
It is not recommended to any other method than the one described below. Your cabling vendor may reject your warranty application if you fail to follow this article.
Items required in addition to a DTX CableAnalyzer:
Inspection is critical. You can use anything from a simple Fiber Viewer to a Video Scope such as the FiberInspector Mini shown above.
If you have no inspection equipment, you cannot proceed.
Let's define what is acceptable and not acceptable.
The Test Reference Cords (TRCs) are critical to a successful measurement.
- NFK1-DPLX-LC Duplex MM 62.5 µm TRC for LC Adapter, Set of 2 (Supports OM1 fiber)
- NFK2-DPLX-LC Duplex MM 50 µm TRC for LC Adapter, Set of 2 (Supports OM2, OM3 and OM4 fiber)
Setting up the DTX CableAnalyzer
- With the DTX-MFM2 fiber modules inserted into the DTX CableAnalyzer, power up the main and remote units.
Sources will need at least five minutes to stabilize, longer in colder or hotter environments.
- Replace the SC Adapters on the main and remote units with the optional LC Adapters.
- Rotate the dial on the DTX CableAnalyzer to SETUP.
- Select Fiber Loss and press ENTER.
- Change the Test Limit to TIA-568-C Multimode.
- Change the Fiber Type to the cable you are testing.
This setting changes the Refractive Index (n) value. The DTX uses n to calculate the length of the fiber. You can manually enter the n values in Tab 3 of the Setup. If you cannot find your cable in the DTX Cable Library, look to the cable vendor's website for their datasheet. Since the TIA-568-C Multimode limit is calculated based on length, it is important to get this value right.
- The Number of Adapters is going to be 2.
This is always the number of adapters per fiber strand added after the reference has been set. (See note below on MPO modules)
- Set the Connector Type to LC.
This will not affect the outcome of the result. It only affects the help screens.
- Set the Test Method to 1 Jumper.
Note: The adapter count is set to 2, even though there are 4 adapters in this link. If you were to set the adapter count to 4, then your loss budget would exceed the 2.6 dB loss requirement of 10GBASE-SR at 300 m. As always, check with your cabling vendor for their warranty requirements.
- Inspect the TRCs. If needed, clean them and inspect again. You will not know if they are clean or not until you have visually inspected them.
- Connect the main and remote units together as shown below.
Failure to use a mandrel will result in fails failures. (That's the red things above)
- Rotate the dial to SPECIAL FUNCTIONS.
- With Set Reference selected, press ENTER then TEST.
- You will then be presented with the results of the Reference.
For 50/125 µm it should be better than -24.50 dBm where -23.50 dBm is better than -24.50 dBm.
For 62.5/125 µm it should be better than -20.00 dBm where -19.50 dBm is better than -20.00 dBm.
These values reflect the cleanliness of the Ports and TRCs. The fact that your reference values are better than the minimum stated above does not mean they are good/clean. In the next few steps, we'll see how good/clean your TRCs really are.
- Press F2 OK.
- You can enter the length of your TRCs here. It does not affect the outcome of the test, but will be displayed on the test report.
- Press F2 OK when done.
- Rotate the dial to AUTOTEST and press TEST.
- We're looking to make sure the sources have stabilized, so with Loss (Remote Main) highlighted, press ENTER.
If you see the loss deviate from 0.00 dB by more than 0.02 dB, your sources have not stabilized. This is an important step to avoid negative loss readings.
- Press EXIT and then highlight Loss (Main Remote) followed by ENTER.
Again, if you see the loss deviate from 0.00 dB by more than 0.02 dB, your sources have not stabilized. This is an important step to avoid negative loss readings.
- Remove the LC connectors from the Input Ports. Never disconnect from the Output Ports. Doing so invalidates the reference you just set.
- Insert one of the LC to LC TRC's into the Input Port on the main unit.
- Insert the other LC to LC TRC into the Input Port on the remote unit.
- You are now ready to test the fiber link, but before you do, let's check out your TRCs. To do this, connect the main and remote units using a singlemode rated LC to LC adapter as shown below.
Note: The use of a singlemode adapter here is deliberate, to assure the best possible alignment of connectors.
- Rotate the dial to AUTOTEST and press TEST.
- To view the result, press ENTER. IGNORE the test limit. We're looking to make sure the loss is no greater than 0.15 dB at both 850 nm and 1300 nm. (The extra 0.05 dB is to take into account the uncertainty of the adapter used above for the TRC verification)
This is the fiber connected to the Input Port of the main unit and it looks good.
- Press EXIT and with Loss (Main Remote) highlighted, press ENTER.
This is the fiber connected to the Output Port of the main unit. ≤ 0.15 dB so we're good to go.
- SAVE the test result so you have evidence of a good Set Reference and submit it as part of your documentation. This will avoid potential disputes later on. The Fluke Networks Technical Assistance Center will be asking for this data if support is required.
- Disconnect the main and remote units.
Place dust caps on the remote TRCs if it is more than a short walk to the other end. According to the EPA, dust in an office can be anything from 2.5 µm to 10 µm so protecting the end faces is critical.
- Connect the TRCs to the link you're testing.
- Press TEST.
Changing the number of adapters/splices will of course increase the test limit. Be sure the Number of Adapters is set correctly.
How often should I Set Reference?
The quick answer is; every time you begin to test a series of fiber links. It is critical to continually inspect the TRCs.