For isolated 1PPS distribution I made this distribution board.

The input is a TLP117 (or similar) optoisolator driving a LT1711 comparator with a 1.0 V trigger level. An output LED-blink is provided by LTC6993. Outputs are driven by IDT5PB1108 buffers.

In jitter measurements with a HPAK 53230A counter the jitter between two 1PPS pulses (from masers) seems to degrade slightly through this amplifier: from RMS 16-19 ps directly on the maser-outputs to between 21 and 26 ps RMS from the outputs of the ISOPDA. Maybe a faster optoisolator would be better?

KiCad sources available on request.