ANSI/TIA-568-C testing LC to LC (Duplex Multimode) DTX-MFM

Last date of manufacture: March 31st, 2006
Replacement product: DTX-EFM2

If you are applying for a cabling warranty, please check with your vendor in advance to see if this method is still acceptable.
 
This article will describe the steps required to successfully certify a multimode LC to LC duplex fiber link in accordance with ANSI/TIA-568-C using the DTX-MFM fiber adapters. ANSI/TIA-568-C requires the user to follow Method B (also known as 1 Jumper) which ensures that the connectors at each end of the link are measured. A 1 Jumper Reference is not possible with these adapters, so an adapted method is used.

Items required in addition to a DTX CableAnalyzer:

Cleaning is critical. It is the single most reason for ending up with negative loss values. You cannot clean without some means of visually inspecting the end face. This can be anything from a simple Fiber Viewer to a Video Scope such as the FiberInspector Mini shown above. If you have no inspection device, you cannot proceed. Let's define what is acceptable and not acceptable.

Perfect. Test Reference Cords are required to be perfect.     No scratches, but there are a few deposits on the end face and whilst they are not on the core, they could move to the core during referencing/testing.          Dirt is clearly covering the core. The hazy stripes across the ferrule indicates poor cleaning practices.        The cladding has been chipped. This could cause damage to anything you insert it into, including the test equipment.

 
The Test Reference Cords (TRCs) are critical to a successful measurement. Your multimode TRCs loss should not exceed 0.10 dB at each end.  And yes, you must inspect and clean these TRCs every time you use them - even new ones out of the bag. We'll show you how to check your TRCs later on in this article.

Where did Fluke Networks get that 0.10 dB requirement?
ANSI/TIA-568-C does not specify a maximum loss requirement for TRCs. However, IEC 14763-3 does and that's where the 0.10 dB for multimode and 0.20 dB for singlemode comes from.

In this example, we're going to test a 100 m (328 ft) duplex 50/125 µm multimode fiber link with LC connectors at each end to ANSI/TIA-568-C. 

Setting up the DTX CableAnalyzer

1. With the 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.
    
2. Rotate the dial on the DTX CableAnalyzer to SETUP.
    
3. Change the Test Limit to TIA-568-C Multimode.
    
4. 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.
    
5. 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.
    
6. Set the Connector Type to LC.
   This will not affect the outcome of the result. It only affects the help screens and is of course recorded with the test result.
    
7. Set the Test Method to 1 Jumper. (Our reference will involve 2 Jumpers, but the result willl be equivalent to the 1 Jumper method)
     
    
    
    
8. Clean AND inspect the TRCs.
    
9. Connect the main and remote units together as shown below with a singlemode rated adapter.
    
   
   
   
   Mandrels must be used. It is a requirement of ANSI/TIA-568-C. Failure to do so can result in good fiber links failing. Red and grey mandrels are shipped with the fiber modules from Fluke Networks. The red is for 50/125 µm and the grey is for 62.5/125 µm TRCs.
    
10. Rotate the dial to SPECIAL FUNCTIONS.
     
11. With Set Reference selected, press ENTER then TEST.
     
12. 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 is better than -24.50 dB.
    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.
     
13. Press F2 OK.
     
14. 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. #3 is the short patch cord we are about to add.
     
      
     
15. Press F2 OK when done.
     
16. Disconnect the remote unit from the main unit.
     
    
     
     
     
17. Insert the short LC to LC TRCs on the remote unit. (Can be on the main or remote unit)
     
    
      
    This adds back in the mated connection that was just referenced out so that our Adapter Count is 2 and not 1. If you did not add the short LC to LC TRCs, then it would be a Method A reference which is not permitted in ANSI/TIA-568-C and the Adapter Count would be 1.
    
     
18. 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.
     
    
     
     
     
19. Rotate the dial to AUTOTEST and press TEST.
     
20. SAVE the test result so you have evidence of a good Set Reference.
     
21. To view the result, press ENTER. IGNORE the test limit. We're looking to make sure the loss is no greater than 0.11 dB @ 850 nm and 0.10 dB @ 1300 nm. (The additional 0.01 dB @ 850 nm comes from the added short LC to LC TRC)
     
    
     
    This is the fiber connected to the Input Port of the main unit and it looks good.
     
    If you see a negative figure here, you need to STOP, inspect and clean the TRCs again and redo the Set Reference.
     
     
22. Pres EXIT and with Loss (Main Remote) highlighted, press ENTER.
     
    
     
    If you see a negative figure here, you need to STOP, inspect and clean the TRCs again and redo the Set Reference.
    
    This is the fiber connected to the Output Port of the main unit. A little more loss than we would hope.
    
    Our 1300 nm result is a little over 0.10 dB. That's ok; we're only talking about 0.03 dB. If it was more than 0.15 dB then you would want to inspect, clean and redo the Set Reference again. 
    
    Can't get anywhere near 0.10 dB? They look ok under the FiberInspector? Your patch cords may not be IEC 14763-3 TRC rated. Please check with the supplier. Most cords come with the test results in the bag.
      
    Tips:
    If you are using the DTX where the temperature is not typical, run the TEST repeatedly with 1 minute intervals to see if the result changes. If it does, you will need to let the sources stabilize and repeat the Set Reference process again.
     
    This procedure is likely to be new to the technician. Have them try this in the office before leaving for the installation.
     
23. 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.
      
     
24. Connect the TRCs to the link you're testing.
    
    
     
     
25. Press TEST.
    
    
    

The DTX CableAnalyzer will calculate the test limit (optical loss budget) for you. 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.