Daisy chain OMC DCPD signals going to split whitening chassis in ISC-R5 U18 through squeezer OMC/homodyne chassis in ISC-R5 U16 (requires DB25 jumper cable).

For the DCPD whitening chassis this should make no difference, and only look like a slightly longer cable. The squeezer OMC DCPD chassis routes all signals straight through, picks off the DCPD signal and extracts the 3.125MHz LO locking signal.