Testing Networks that contain Optical Splitters

Applies to

MAX-700B/C/D series, OX1 instruments, PON testing


The testing and characterization of Passive Optical Networks (PON) includes some unique challenges; FTTx networks are typically fairly short (compared with transport networks), but the losses introduced by splitting optical signals requires the use of comparatively long pulse widths to test, which can present resolution issues. This has resulted in the development of specialized instruments.

EXFO's FTTH PON Guide provides extensive information and background on PON testing.

When performing testing on networks involving tandem passive optical splitters, you should be careful to ensure that the fiber section following the splitter/s are a suitable length, such that intelligent processing software like EXFO's intelligent Optical Link Mapper (iOLM) are able to accurately perform loss measurements and appropriately characterize network elements.



Instruments and applications specifically designed for 'last mile' PON testing, such as the OX1 and iADV 'Optimode: PON Last-Mile Certification' are not optimized for testing networks with multiple splitters; these require more specialized OTDR instruments.

Please check instrument specifications carefully and if in any doubt contact EXFO Technical Support for further assistance.


The non-exhaustive table below provides the minimum fiber lengths required following a single splitter for several different instruments:

Splitter/Group Ratio Typical Loss MAX-715B MAX-730C/735C OX1
1:2 3dB 30m 25m 25m
1:4 6dB 150m 100m 35m
1:8 9dB 400m 150m 150m
1:16 12dB 1500m 400m 250m
1:32 15dB 4500m 1000m 500m
1:64 18dB NA 3000m 1000m


In the case of multiple (cascaded) splitters, the span length required following the next splitter (toward the 'far' end of the link) is that of the Group (combined) Ratio.

For example, the network shown below is being tested from the customer premises using a MAX-730C instrument and includes a 1:4 (iOLM 'stage 2 splitter') followed by a 1:8 (iOLM 'stage 1 splitter') optical splitter.

Consulting the table above for the MAX-730C, the minimum fiber length required following the first 1:4 splitter is 100m, whereas the minimum fiber length required following the 1:8 splitter is then instead 1km, since the Group Ratio is now 1:32 (4 * 8 = 32) for the cascade topology.