Abstract

Directly modulated lasers (DMLs) have long been employed for short- and medium-reach optical communications due to their low cost. Recently, a new modulation scheme called complex modulated DMLs has been demonstrated showing a significant optical signal to noise ratio sensitivity enhancement compared with the traditional intensity-only detection scheme. However, chirp-induced optical spectrum broadening is inevitable in complex modulated systems, which may imply a need for high-bandwidth receivers. In this Letter, we study the impact of receiver bandwidth effects on the performance of complex modulation and coherent detection systems based on DMLs. We experimentally demonstrate that such systems exhibit a reasonable tolerance for the reduced receiver bandwidth. For 10 Gbaud 4-level pulse amplitude modulation signals, the required electrical bandwidth is as low as 8.5 and 7.5 GHz for 7% and 20% forward error correction, respectively. Therefore, it is feasible to realize DML-based complex modulated systems using cost-effective receivers with narrow bandwidth.

© 2016 Optical Society of America

Duobinary pulse shaping for frequency chirp enabled complex modulation

Di Che, Feng Yuan, Hamid Khodakarami, and William Shieh
Opt. Lett. 41(17) 3968-3971 (2016)

Complex modulation and detection with directly modulated lasers

Qian Hu, Di Che, Yifei Wang, Feng Yuan, Qi Yang, and William Shieh
Opt. Express 23(25) 32809-32819 (2015)

Beyond amplitude-only detection for digital coherent system using directly modulated laser

Qian Hu, Di Che, Yifei Wang, An Li, Jian Fang, and William Shieh
Opt. Lett. 40(12) 2762-2765 (2015)

Towards high-order modulation using complex modulation of semiconductor lasers

Di Che, Feng Yuan, and William Shieh
Opt. Express 24(6) 6644-6649 (2016)

Transmission of 2 × 56  Gb/s PAM-4 signal over 100  km SSMF using 18  GHz DMLs

Shiwei Zhou, Xiang Li, Lilin Yi, Qi Yang, and Songnian Fu
Opt. Lett. 41(8) 1805-1808 (2016)