Optical Beat Interference Free in a Cascade Add/Drop Transceiver Structure of Passive Optical Networks

　　　　　A cascade add/drop transceiver (CAT) structure for subcarrier multiplexed passive optical networks (SCM-PONs) is demonstrated to solve optical beat interference (OBI) problem. The proposed CAT structure can completely eliminate OBI in the SCM-PON. Our experiment indicates that 3 ONU's are on upstream direction and at the same time there are signals transmitting downstream direction. This approach by having bit rates of 3 Mbit/s in different modulation frequency band can eliminate the OBI problem and still maintain a good transmission quality.