Comparison of PAM and CAP Modulation Schemes for Data Transmission Over SI-POF

An experimental comparison of multilevel modulation schemes for polymer optical fiber (POF) transmission systems is shown in this letter. The performance of a non-return-to-zero, pulse-amplitude modulation (PAM), and carrierless amplitude phase (CAP) modulation was tested under the different conditions, including various link lengths and fiber-coupled power. As an optical transmitter, the commercial laser diode operating at 655 nm was used. A maximum bit rate of 5 Gb/s over 50-m 1-mm step-index POF link was achieved with 16-CAP modulation format at +6 dBm fiber-coupled power and a bit-error ratio of 10
^-3
. Over 100 m, a maximum bit rate of 3.4 Gb/s was realized with 4-PAM.