Supervisory signal transmission by modulating the mB1C code complementary bit

A supervisory signal transmission method for digital optical communication systems is proposed. It minimizes circuit scale, clock frequency increase, and interference between traffic and supervisory information, and does not require customization. The supervisory signal is carried by the amplitude-modulated complementary bit in the mB1C coded sequence. The code adds a single bit after every m bit block as a complement to the last bit of the block. Clock frequency increase is kept at a level of (m+1)/m. This additional bit is called the C bit. If the C bit´s amplitude is modulated according to the supervisory (SV) signal and the main data block is not modulated, traffic and supervisory information can be isolated in time over the same fiber transmission