Optical band-pass filter (1600-1670 nm)

If an existing FJL is augmented with additional network segments onto an already live splitter, OTDR testing is not possible without using a 1600-1670 nm optical band-pass filter in-line with the launch lead. However, the OTDR testing is then limited to 1625 nm in order to avoid interference with the NTDs that transmit on 1310 nm.

Thus, the preferred option is to OTDR test the new network segment prior to splicing it onto the live splitter.

The typical insertion loss for this devise is 0.4 to 0.6 dB. The filter also adds additional length prior to the launch lead used. The use of a band-pass filter on a live network is less preferred alternative, as the 1310 nm test results are then not provided, resulting in not being able to detect pressure points.

On the other hand, the splice at the exit of the splitter in the FJL becomes visible when using the band-pass filter. However, PON level readings will instead be used to estimate the splice loss in the splitter at the FJL.