I am an enthusiastic technician who was fortunate enough to acquire an OmniSwitch 6400 for free.
Since the console adapter was not provided, I managed to create a small cord myself.
During my internet research, I found that this site was very popular.
I thought it was the perfect place to share this little tutorial.

I bought this adapter from Amazon. But surely any same kind of Cisco adapter based on FTDI chip will do the job.
An RJ45/console to USB adapter: → USB to RJ45 Console Cable with FTDI Chip
Since this type of connector is intended for Cisco and other hardware, it won't work as is with Alcatel devices.
You need to create a small adapter cable to reverse the TXD/RXD signals.
Only the 4 middle wires are useful on the OmniSwitch 6400 (basic RS232 without flow control signals).
Inversion to be done:
1 → NC
2 → NC
3 → 6
4 → 4
5 → 5
6 → 3
7 → NC
8 → NC
Connect everything with an RJ45 female/female inline coupler and you're good to go.
This gives us a cable that can work with many different brands and can also work with the Alcatel 6400 series with the adapter.

In my case, I used an RJ11 connector since only 4 wires are required.
It is working perfectly.
I hope this can be helpful to anyone.
I attached a few pics.