Apparatus and method for transmitting a supervisory signal for optical network applications. The apparatus includes a subcarrier transmission system configured to receive a first supervisory signal and output a second supervisory signal, and an electrical-to-optical conversion system configured to receive the second supervisory signal and a data signal and output an optical signal. The second supervisory signal is associated with a subcarrier frequency. The data signal is associated with a data bandwidth, and the data bandwidth includes a data frequency. At the data frequency, a power density of the data signal is substantially equal to zero. A ratio of the subcarrier frequency to the data frequency ranges from 0.8 to 1, and the subcarrier frequency ranges from 2.4 GHz to 2.483 GHz.