Optical Supervisory Channel (OSC) Card provides an optional out-of-band management channel for communication between Cisco ONS 15530 systems. The OSC uses a 33rd wavelength to carry control and management traffic, such as defect indications, performance information, and automatic protection switching information. Up to two OSC modules can plug into a Cisco ONS 15530 carrier motherboard. Two OSC modules can be used to provide redundant communication between interconnected Cisco ONS 15530 systems. The OSC is ITU channel 19 with a wavelength of 1562.23 nm.