We could calculate the frequency
that the communication system uses, if we knew how fast the signals travel through the fibres and how long the fibres are.
Naturally we also would need to know whether the carrier signals are electrostatic, magnetic, electromagnetic, or zero point energy, then if we could figure out the method of modulation and the language of the communication we could understand what the communication consists of, unless it is encrypted, in which case we would need to figure that out too. :-)