FIBRE OPTIC TESTING
Table 1 : The TIA-568.3-D ( 2016 ) standard
Lastly , if the make and model of the network equipment is known , the specifications for the following can be found :
1 . Loss limits based on specific applications , typically a variation of Ethernet .
2 . Loss budget calculations based on the actual networking equipment that will be operating on the installed cabling .
We ’ ll look at each of these situations in detail so that you can determine the limits for acceptable attenuation / insertion loss in any situation .
Cabling based loss budgets
Most cabling installers will use this method for determining the amount of loss that is acceptable for certification of the cabling following installation . Using an optical power meter and light source or OLTS ( Optical Loss Test Set ), Tier 1 Certification can be performed against industry standard limits for cable and connectors . Both the TIA and ISO cabling standards list the acceptable loss limits for fibre optic components and these values can be used to calculate a loss budget . The upside is that the installer needs to have no knowledge about the operational network to calculate the loss budget . The downside is that a loss budget needs to be calculated for each fibre cable - not fibre strands within a cable , but for each cable between two points .
The TIA-568.3-D ( 2016 ) standard [ table 1 ] lists the transmission performance parameters for optical fibre .
Calculating the loss budget for cabling using the table above is very straightforward . To make the process easier , some testers , for instance the Ideal Networks LanTEK III with FibreTEK III modules , have built-in loss budget calculators that allow the user to enter the variables and automatically determine the loss limit .
Using application specific limits
The easiest way to determine a loss budget is when the application that the fibre will support is known . In these cases , it ’ s simply a matter of looking up the requirements for each application .
There are many available resources that list various requirements for different applications . Above is an excerpt from the TIA-568.0-D standard that lists requirements for a few
Optical fibre type Wavelength ( nm ) |
Maximum attenuation ( dB / km ) |
Minimum overfilled modal bandwidthlength product ( MHz × km ) |
Minimum effective modal bandwidthlength product ( MHz × km ) |
850nm laser optimised , 50 / 125 μm Multimode , ( OM3 ) |
850 1300 |
3.0 1.5 |
1500 500 |
2000 Not required |
850nm laser optimised , 50 / 125 μm Multimode , ( OM4 ) |
850 1300 |
3.0 1.5 |
3500 500 |
4700 Not required |
Single-mode indoor / outdoor |
1310 1383 1550 |
0.5 0.5 0.5 |
N / A N / A N / A |
N / A N / A N / A |
Single-mode inside plant |
1310 1383 1550 |
1.0 1.0 1.0 |
N / A N / A N / A |
N / A N / A N / A |
Single-mode outside plant |
1310 1383 1550 |
0.4 0.4 0.4 |
N / A N / A N / A |
N / A N / A N / A |
Connectors / splices |
|
Maximum attenuation ( dB ) |
|
|
Connector pair 0.75 Splice ( fusion / mechanical ) 0.3
February 2017 | 29