A network including an optical sensing device and a registration server, wherein a secret key and a unique public identifier are installed in a non-volatile memory of the optical sensing device and in a database of the registration server, before the optical sensing device is connected to the network; wherein, the registration server is adapted to authenticate the optical sensing device when the optical sensing device is connected to the network by verifying the optical sensing device's encryption, using the secret key, of a challenge message; wherein, if the authentication succeeds, the optical sensing device is registered in the database of the registration server.