Demonstration of RZ-OOK modulation scheme for high speed optical data transmission

The optical communication has gained enormous popularity as an effective means of transferring data at high rates because of extremely high bandwidth access and cost effectiveness. On-Off keying (OOK) modulation scheme with direct detection is the most widely used intensity modulation scheme for optical communication. OOK can use either nonreturn-to-zero (NRZ) or return-to-zero (RZ) pulse formats for communication. RZ modulation format is becoming increasingly popular for high speed data transmission due to its superior performance over conventional NRZ format. In this paper, we demonstrate the design and implementation details for RZ-OOK modulation scheme for various duty cycles. The experimental setup and test results for 1 Gbps RZ-OOK transmitter has also been presented. This RZ-OOK transmitter consists of a laser diode followed by two Mach-Zehnder (MZ) modulators connected in cascade. We also present analysis and simulation results such as eye diagram, optical spectrum etc. for RZ-OOK as well as NRZ-OOK modulation schemes for data rates upto 10 Gbps.