What is the accepted maximum loss for splicing joint and connectors when test by Exfo Otdr?

Individual Splice Loss of0.05 dB and total splice loss cannot increases0.1 dB.

Connector Loss should not increase more than0.5 dB.

Well, you really want to check with your client about the standard he follows. However, regardless of the brand of the OTDR, ITU-T L.12 specify an average loss of less or equal to0.1dB..You need to conduct bidirectional test and average the splice loss to avoid the misleading reading due to MFD mismatch.

This is simply because of the fact that OTDR do not measure the loss. OTDR calculates the loss only. OTDR measures backscattering and Fresnel reflection of the fiber. Using the value of the backscattering and Fresnel reflection, OTDR calculates the loss of each event in the fiber (connector, splice … etc).

Therefore when splicing two fibers with slightly different Mode Field Diameters (MFD), OTDR thinks that the attenuation of the fiber section after the splice is higher than the attenuation of the section before the splice (in case the MFD of the fiber after the splice is smaller than the MFD of the fiber before the splice which in turn will result in a higher backscattering level after the splice than the backscattering level before the splice). Therefore, OTDR read negative splice values (gainers)!

On the other hand, OTDR over estimates the splice loss in case the MFD of the fiber before the splice is smaller than the MFD of the fiber after the splice.

Please avarage the loss in both directions and agree with your client about the standard

Splice loss depends not only on the splicing process but also on the differences between the two spliced cables characteristics such as Mode Field Diameter (MFD) and back scattering etc.

The best splice loss result is when the same cable cut and re-spliced again because there is matched MFD and back scattering. In this case the splice loss is mainly depends on the splice process and it could be very low (0 to0.01 or0.02 maximum).

Suppose you splice two different cables with MFD=9.2 +/-0.4 then at the most extend MFDs and if one spliced cable has MFD =8.8 and the other one has MFD =9.6 then the MFD difference will add0.033 db loss and then you may consider the worst average splice loss =0.05

Spliss loss due to MFD missmatch = -10 log (4 / (MFD1/MFD2 + MFD2/MFD1)^2 )

Average splice loss = Losses due to MFD mismatch (0.033) + machine splice loss (0.02 maximum) =0.053

Connector loss usually below0.3 db but when you measure you may take into consideration the pigtail splice loss as mostly the OTDR will add it to the connector loss because usually the pig tail is short (about2 meters) and then:

Apparent connector loss = Actual connector loss + one direction pigtail splice loss

=0.3 +0.15 (or0.2 maximum) =0.5 db

Currently, polished connectors has low losses and by practice you can consider the connector loss + pigtail splice loss <0.3 db