To use SPI over a 5m long cable we plan to use LVDS RS-644 which calls for a twisted-pair cable with 100ohm characteristic impedance.
Evaluating our cable options we looked into Cat5 cable (originally for ethernet but perfect for LVDS), but unfortunately we need at least 5 pairs: 4 pairs for SPI (reception, transmission, chip select and clock) plus two wires for symetric power whereas Cat4 provides only 4 pairs.
We seem to come across all kinds of high quality 100ohm cables with more than 4 twisted pairs but all seem to be specialty products. Ethernet cables (only 4 pairs) are available with ease but the rest are much more difficult to source.
Any suggestions on other cable standards that could facilitate sourcing them in short lengths but still be specified as 100ohm for high-speed data links?