With fiber optic cabling, there is the option to use a multiplexer (MUX) in order to send more information across a single strand of fiber to improve throughput and efficiency. This is analogous to 'etherchanneling' with the exception that all of the signals are going across a single fiber pair. This involves putting the fiber between two MUXes. The MUXes will code and decode the wavelengths into their separate signals.
This article provides information regarding how Exinda appliances support and work with Fiber Multiplexing.
If putting an Exinda between the two MUXes, it is not possible for the standard fiber NICs on the device to interpret the multiple wavelengths used by multiplexing and thus it will not be able to get information regarding all the individual signals. In order to do so, a multiplexing NIC would need to be installed, which is not possible on the Exinda appliances.
The Exinda needs to be placed before a MUX connection is started, or after a MUX connection is terminated so that it can read each connection individually instead of in one pulse. Having one in the middle between the endpoints of a connection will result in the traffic passing, but no data being captured by the Exinda about the traffic.