The invention relates to a remote interface device (12) for terminating a remote optical fiber link, with a network input (14), a network output (15), a customer input (17) and a customer output (16) for data signals, characterized in that the device (12) is designed such that during normal operation, only data received at the customer input (17) is sent onto the network output (15), that the device (12) is further designed such that in case of a failure at the network input (14) or a failure at the hardware of the remote interface device (12), the network output (15) is closed, i.e. no signal at all is sent onto the network output (15), and in case of a failure at the customer input (17), a dedicated auxiliary signal only is sent onto the network output (15). The inventive device allows the use of the full data transfer capacity for customer's data during normal operation, and allows distinction between different types (provider, customer related) of connection failures.