OC-12: Optical Carrier Level 12; 622 megabits rate.
OC-3: Optical Carrier Level 3; 155 megabits rate.
OFDM: Orthogonal Frequency Division Multiplexing: A digital transmission method optimized for over the air broadcast.
ONU: Optical network unit: Optical to electrical signal converter
OSI: Open System Interconnection: A standard delineation of network communication functions into 7 discrete layers These layers are: 1) Physical Layer; 2) Link Layer; 3) Network Layer; 4) Transport Layer; 5) Session Layer; 6) Presentation Layer; 7) Application Layer.