Fig. 1. Illustration of the proposed DD–PolMux multi-band CAP system.

Fig. 2. Experimental setup of the 56  Gb/s DD–PolMux two-band CAP system. TIA, transimpedance amplifier.

Fig. 3. Optimal bandwidth of the optical filter for x- and y-polarizations.

Fig. 4. Spectra of the following: (a) two-band CAP signal in the lower branch; (b) combined x- and y-signals after the PBC; (c) signals after the 15 km fiber link; (d) signal in the lower branch after the filter at the receiver.

Fig. 5. BER curves of 56 Gb/s DD–PolMux two-band CAP system for back-to-back and 15 km SSMF transmission.