I need to perform return loss measurements on multimode cable. Will 8161x RTL modules allow me to do so?

All Keysight Kurt RTL modules (81610-14A) have singlemode fibres internally. Therefore the specifications of the RTL modules are only valid if connecting a singlemode fiber to the output of the module, since using a multimode fiber leads to insertion loss and reflection at the interconnection. Specifications are not valid if using a multimode cable. See also specification sheet of RTL modules "Fiber type."