Fig. 1. Structures of SV-DD transmitters: (a) polarization division multiplexing based on intensity modulation and (b) polarization division multiplexing with signal-carrier.

Fig. 2. Structures of SV-DD receivers. (a) Receiver A: with two BPDs, two PDs, and a 90° optical hybrid. (b) Receiver B: with four PDs, and a 90° optical hybrid. (c) Receiver C: with four PDs and a 3×3 coupler.

Fig. 3. Normalized noise power as a function of the coupler splitting ratio of the PDM-IM: (a) for receiver A, (b) for receiver B, and (c) for receiver C.

Fig. 4. Normalized noise power as a function of the coupler splitting ratio of the PDM-SC: (a) for receiver A, (b) for receiver B, and (c) for receiver C.

Fig. 5. Simulation results for the PDM-IM system: (a) BER vs. coupler splitting ratio for different SOPs for receiver A, (b) BER vs. coupler splitting ratio for different SOPs for receiver B, (c) BER vs. coupler splitting ratio for different SOPs for receiver C, and (d) BER vs. received optical power for different SVRs in BTB transmissions.

Fig. 6. Simulation results for the PDM-SC system: (a) BER vs. coupler splitting ratio for different SOPs for receiver A, (b) BER vs. coupler splitting ratio for different SOPs for receiver B, (c) BER vs. coupler splitting ratio for different SOPs for receiver C, and (d) BER vs. ROP for different SVRs in BTB transmissions.

Fig. 7. Simulation results with 2.5 dB EL for the 90° hybrid and 0.15 dB EL for the 3×3 coupler: BER vs. coupler splitting ratio for different SOPs (a) for receiver A for the PDM-IM system, (b) for receiver A for the PDM-SC system, (c) for receiver C for the PDM-IM system, and (d) for receiver C for the PDM-SC system.

Table 1. General Simulation Parameters of 112 Gbit/s PDM-DD Systems

Table 2. Comparison of 112 Gbit/s PDM-PAM4 and PDM-SC Signals with Different SV-DD Receivers. IM: Intensity Modulation; I/Q: I/Q Modulator; BPD: Balanced Photodetector