  In this work we analyse and demonstrate the coexistence of digital coherent
and analogue radio over fibre signals over an access-metro transmission network
and field fibre. We analyse how the spectral proximity of the two signals and
the non-ideal filter alignment of typical telecomms-grade ROADMs affect the
signal performance. Our results show that coexistence is indeed possible,
although performance deteriorates with the increase in number of ROADMs in the
network topology. Thus, while todays access-metro networks will be able to
support future 5.5 and 6G cell densification operating at mmWave and THz
frequency, using spectral efficient analogue radio over fibre transmission,
there will be trade-offs to be considered. In our experiment setup, we show
that the limit for ARoF accessible performance is reached after transmission
over 3 ROADMs and a total of 49 km of fibre.
