Subchannel security at the optical layer

A method of providing security at the physical layer of an optical network by processing client signals for transmission on a fiber optic cable of the optical network, the fiber optic cable carrying a plurality of ITU (International Telecommunications Union) channels, each ITU channel having a corresponding ITU carrier frequency and a plurality of subchannels, each of the subchannels having a corresponding subcarrier frequency within that ITU channel, the method comprising the following steps:

• (a) encoding a plurality of client signals;
• (b) buffering and synchronizing the encoded client signals;
• (c) tuning a distinct laser to generate a corresponding subcarrier frequency within each ITU channel, and mapping the buffered and synchronized encoded client signals to respective subchannels of the ITU channels, wherein each subchannel of the ITU channels corresponds to a subcarrier frequency of its corresponding ITU carrier frequency generated by one of the distinct lasers;
• (d) modulating each subchannel of the ITU channels onto the subcarrier frequency of its corresponding ITU carrier frequency;
• (e) multiplexing together those subchannels of the ITU channels whose corresponding frequencies fall within the same ITU channel to create a plurality of ITU channel signals, and multiplexing the ITU channel signals to generate and transmit an optical signal along the fiber optic cable of the optical network;
• and
• (f) modifying dynamically over time one or more of the processing steps (a)-(e).