I have an electric Fender acoustic guitar which should be strung only with nylon strings. There are two basic pick-ups which work with nylon strings.
One is the Piezo Pickups: These are typically mounted under the bridge saddle. When nylon strings vibrate, they transfer energy to the bridge, causing the piezo crystal to generate an electrical signal. This signal is sent to an amplifier. The other is the Microphone Pickups: These capture the sound waves produced by the vibrating nylon strings and the guitar’s body, converting them into an electrical signal.
The signal from either pickup type is often processed through a preamp to boost the output and shape the tone, as nylon-string guitars produce a softer, warmer sound compared to steel-string guitars.