15
TEST & MEASUREMENT
15
Optical fibre type Wavelength ( nm ) |
Maximum attenuation ( dB / km ) |
Minimum overfilled modal bandwidth-length product ( MHz-km ) |
Minimum effective modal bandwidth-length 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 |
If the installer knows what the client plans to run on the system , they can refer to the standards for that application to determine acceptable loss . Also , if the make and model of the network equipment is known , installers can look to the specification for loss limits based on specific applications , typically a variation of Ethernet , and loss budget calculations based on the actual networking equipment that will be operating on the installed cabling .
Cabling-based loss budgets Cabling-based loss budgets are a popular method for determining the acceptable loss for certification of the cabling following installation . Using an optical power metre 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 TIA-568.3-D ( 2016 ) standard lists transmission performance parameters for optical fibre ( see charts above and right ). To make the process easier , some testers like testing modules that have built-in loss budget calculators so you can enter the variables and automatically determine the loss limit . Take an example of a simple 90-metre horizontal multimode cable link with a patch panel at one side and a work area outlet at the other . Using the same concept , lets calculate the budget for a 1,500-metre multimode link with two splices and a connection at each end .
The previous calculations tell the installer what the pass / fail limit in the tester needs to be set to in order to certify each of the links to TIA / ISO cabling standards . In this case , the measured insertion loss needs to be less than 6.10dB at 850nm and 3.85dB at 1300nm for the link to pass . Keep in mind that this calculation is for the cabling only . It does not take into account the communication application that will be running over the link . Some applications in the table below won ’ t operate over this link because it exceeds both the length and insertion loss allowances .
For example , a 10GBase-LX4 ( 10G Ethernet at 1300nm ) allows a maximum loss of 2.0dB and a maximum distance
Connectors / splices
Standard grade connector pair
Reference-to-Standard grade connector pair
Splice ( fusion / mechanical )
Maximum attenuation
0.75 dB
0.50 dB
0.30 dB
of 300 metres ( yellow highlight ). A 1,500-metre link with up to 3.85dB of insertion loss exceeds both the insertion loss and length limits of 10GBase-LX4 . 100Base-FX ( 100Mb Ethernet at 1300nm ) highlighted in green allows a maximum insertion loss of 6.0dB and a maximum length of 2,000 metres . The example link will support 100Mb Ethernet if the test passes the limits determined by the loss budget calculation .
Panel Connection 1 Panel Connection 2
90m multimode cable www . networkseuropemagazine . com