SLQ4 board is hardly fully utilize in slot 1 to slot 4 in OSN 3500 although the slot capacity can support until 5G.
When the cross-connect capacity is 80 Gbit/s or 200 Gbit/s（S/I XCS）, for the board housed in any of slots 1–4 and 15–16, two optical interfaces can be configured. For the board housed in any of slots 5–8 and 11–14, four optical interfaces can be configured.
The Slot 1 to 4 of OSN 3500 was created for the utilization of the smaller capacity service board. So SLQ 4 is pretty suggested on slot 4 above .
The cross-connect board (N1E/IXCSA/B) supports two compatible backplane rates of 622M and 2.5G. Other boards support only one fixed backplane rate. The N1SLQ4 needs 4 buses at a rate of 622M. The cross-connect board (N1E/IXCSA/B) has two buses in slots 1–4 and 15–17, four buses in slots 5, 6, 13 and 14, and 16 buses in slots 7, 8, 11 and 12. Therefore, the SLQ4 can be installed only in for 2 optical boards which can connect to 2 buses.
The cross-connect board supports two compatible backplane rates of 622M and 2.5G. Other boards support only one fixed backplane rate. Hence, consider both the access capacity of each slot and the bus distribution of the cross-connect board for board installation. This method also works for other line boards.
The backplane designed can be improved for this situation to giving customer more option for utilization on different capacity service board on the sub rack OSN .