Modulator-free quadrature amplitude modulation signal synthesis
Collaborating with colleagues at Optoelectronics Research Centre (ORC) and Eblana Photonics, we develop an approach that enables direct modulation of laser currents to be used to generate highly advanced modulation format signals.
While direct modulation of a semiconductor laser’s drive current enables fiber-optic communications at speeds of around 2.5 Gbit/s, higher-speed operation using direct modulation has historically been confounded by frequency chirp, forcing commercial 10 Gbit/s systems to use an external electro-optic modulator. For increased capacity (100 Gbit/s and beyond), coherent systems were recently commercialized that also use external electro-optic modulators to deliver complex modulation formats.
Our new approach has skirted this historical limitation through a modulator-free, optical-injection-locking method that brings the benefits of direct modulation back to the modern coherent telecommunications network.
Please find the details report at Laser focus world
1. Z. Liu et al., Nat. Commun. 5, 5911 (Dec. 2014); http://dx.doi.org/10.1038/ncomms6911.