Abstract: A return-to-zero control signal for controlling a modulator can be generated from two separate streams. A first data stream can include a pulse for each logical one that appears in an input data stream, while a second data stream can include a pulse for each logical zero that appears in the input data stream. The first and second data streams can be combined in a manner that yields the return-to-zero control signal. The first and second data streams can be generated in digital circuitry, such as an FPGA, to minimize the analog path for generating the return-to-zero control signal.

Abstract: A method for monitoring an optical network includes communicating optical traffic along a working path of an optical network. The optical network comprises a protection path for the optical traffic to communicate the optical traffic upon a failure in the working path. The protection path comprises two or more network elements coupled together by optical lines. The method also includes monitoring an idle signal of the protection path to detect an error in the protection path comprising an error in a component of one or more of the network elements.

Abstract: A method is provided for monitoring a network that includes providing a path selector that can select between a first input and a second input, where the first input is coupled to a customer premises equipment interface that is operable to receive signals from customer premises equipment and the second input is coupled to a test signal generator that is operable to generate test signals. The method also includes determining whether operating customer premises equipment is coupled to an input of the customer premises equipment interface that is coupled to the first input of the path selector. If not, then an idle state is entered into. While in the idle state, it is determined whether a signal is received from the customer premises equipment interface at the first input of the path selector. The test signal received at the second input of the path selector is selected unless a signal is received from the customer premises equipment interface at the first input.