Relaxed laser control of uncooled multiple-input and multiple-output dense wavelength-division multiplexing systems for low power consumption data communication links

A simulation-based assessment is made of the benefits of using advanced modulation formats including pulse amplitude modulation (PAM) and carrierless amplitude/phase modulation (CAP) to ease laser control requirements of a recently proposed novel uncooled multiple-input and multiple-output wavelength-division multiplexing (WDM) system. At a per channel bit rate of 25 Gb/s, the spectral efficiency improvements inherent to these schemes provide additional optical system power margin over non-return-to-zero (NRZ) modulation (0.4 dB for PAM-4 and 4.4 dB for CAP-16) for a link distance of 20 km. This allows the minimum channel spacing between channels to be reduced from 0.4 nm (NRZ) to 0.3 nm for PAM-4 and to 0.14 nm for CAP-16, this in turn allowing for a more stable operating region to be realised. Compared with a traditional 16 × 25 Gb/s dense WDM system, a power consumption saving of 30% can be realised using NRZ whereas PAM-4 and CAP-16 offer 29 and 27% savings, respectively.