1 Department of Photonics Engineering, Technical University of Denmark2 Metro-Access and Short Range Systems, Department of Photonics Engineering, Technical University of Denmark3 Technical University of Denmark
In this letter, we present experimental investigations of multidimensional multilevel carrierless amplitude phase (CAP) modulation with directly modulated vertical cavity surface-emitting lasers. The signals are transmitted over 20 km of standard single-mode fiber (SSMF). For multilevel 3-D-CAP, bit rates of 468.75 and 937.5 Mb/s are achieved at two levels/dimension and four levels/dimension, respectively. For 4-D-CAP, bit rates of 416.67 and 833.3 Mb/s are achieved at two levels/dimension and four levels/dimension, respectively. For all signals, a bit-error rate below the forward error correction limit of 2.8 × 10-3 for error-free reception is achieved after 20 km of SSMF transmission. Spectral efficiencies of 2.68 and 2.08 b/s/Hz are reported for 3-D-CAP and 4-D-CAP, respectively. We believe that multidimensional modulation formats represent an attractive solution for providing more flexibility for optical fiber systems.
I E E E Photonics Technology Letters, 2012, Vol 24, Issue 22, p. 2009-2012
Carrierless amplitude and phase; Multilevel multidimensional modulation; Vertical-cavity surface-emitting laser (VCSEL) optical communication