This standard defines two methods for measuring fibre optic links, often referred to as the three jumper and one jumper methods.
Note: You cannot use the DTX-GFM2 (VCSEL) with this test limit/standard. Since the OptiFIber has no VCSEL source
for loss/length testing, this is not an issue. IEC14763-3 is very specific about the coupled power ratio (CPR)
requirement for multimode sources. At 850 nm for 62.5/125 µm fibre, the CPR must be 25.5 dB +/- 0.5 dB.
For the DTX-GFM2, the CPR is approx. 13 dB, because it uses a VCSEL source.
The default test method for the attenuation measurement of links and channels in this standard is the 3-jumper method. This method is generic and can be used for measuring the attenuation of both channels and links regardless of the type of connector interface on cabling and equipment. It is not the same as the three jumper method found in ANSI/TIA/EIA-526-7 Method A.3 and ANSI//TIA-526-14B Method C.
A reference is first established to mitigate the test reference cords as shown below:
* For multimode, a mandrel is required at the output ports
For this method to work, extreme care must be taken to ensure that the connectors on the field calibration cord are of reference quality. The standard defines reference quality cords in section 6.3.2, Table 3 shown below:
Table 3 from IEC 14763-3
This may cause difficulty for the user. Most patch cord vendors/suppliers operate to a connector loss of better than 0.3 dB. The user may have to purchase multiple patch cords in order to find three Test Reference Cords that meet the requirements of Table 3 in IEC 14763-3. In order to help users, the Test Reference Cords from Fluke Networks are guaranteed to meet Table 3 in IEC 14763-3.
The middle Test Reference Cord is then removed:
And the main and remote units connected to the fibre link to be tested:
The Adapter Count is 0 in the OptiFiber for the link above.
At first, it would seem that this method excludes the measurement of the connectors at each end of the link, since these were referenced out earlier. By adjusting how the test limit is calculated and taking into account the original reference values, it is possible to measure the installed link including the quality of the connectors at each end of the link.
- In Table 3, it states that the attenuation between 2 reference connectors must be less than 0.1 dB for multimode and 0.2 dB for singlemode.
- In Table 4, it states that the maximum Insertion Loss (compared with the losses in the reference configuration) is 0.3 dB for each connection when testing multimode and 0.5 dB for each connection when testing singlemode.
The loss limit for multimode is calculated as:
Loss of fibre under test + Loss of Splices + Loss of Connectors - 0.1 dB - 0.1 dB + 0.3 dB + 0.3 dB
The loss limit for singlemode is calculated as:
Loss of fibre under test + Loss of Splices + Loss of Connectors - 0.2 dB - 0.2 dB + 0.5 dB + 0.5 dB
For this singlemode fibre link:
The loss limit would be: 1.0 dB - 0.2 dB - 0.2 dB + 0.5 dB + 0.5 dB = 1.6 dB
An addendum to IEC 14763-3 gives the forumale in an easier way to understand. Using the default three test cord reference method specified in 9.1.12, the permanent link limits are as follows:
- for MMF: Limit = 0.4 dB + Σ (cable attenuation) + Σ (embedded connection attenuation)
- for SMF: Limit = 0.6 dB + Σ (cable attenuation) + Σ (embedded connection attenuation)
The one jumper method
You are still permitted to use the traditional one jumper method when:
- Your connectors in the fiber link are the same as those on the testers fiber ports, (SC connectors for OFTM-5612 & OFTM-5632)
- Or the tester has interchangeable adapters on the inputs (OFTM-5712 & 5732 with DTX-xFM2 Series).
The reference method below may seem a little strange at first, but it is logical. The first advantage is obvious. There are no adapters (connector pairs) in the reference. The Test Reference Cords here still need to meet the requirements of Table 3.
Once the reference is set, the fibres at the INPUTS ONLY are removed:
And the dangling connector from the other duplex lead is connected to the INPUT ports.
The link can then be measured as shown below:
The Adapter Count is 2 in the DTX for the link above.
The loss limit would bet = 1.0 dB + 1.0 dB = 2.0 dB
An addendum to IEC 14763-3 gives the forumale in an easier way to understand. Using the alternative one cord reference method specified in 9.1.12, the permanent link limits are as follows:
- for MMF: Limit = 0.6 dB + Σ (cable attenuation) + Σ (embedded connection attenuation)
- for SMF: Limit = 1.0 dB + Σ (cable attenuation) + Σ (embedded connection attenuation)
If you calculate the loss limit in this example using the three jumper reference method, the loss limit is 1.6 dB. Calculating the loss limit using the one jumper reference method, the loss limit is now 2.0 dB. Installers will have a much tougher time passing the three jumper method compared to the traditional one jumper method. But, the three jumper method does provide a universal method that can be used for all connector types and where the interface to the test equipment is not the same as the link under test.
Which is best, three jumper or one jumper?
Both methods have their advantages and disadvantages. If you intend to apply for a warranty on the installed fiber cabling, you should consult with the cabling vendor offering the warranty to confirm their test requirements.