Electroabsorption-modulated laser as optical transmitter and receiver: Status and opportunities

Abstract

The rapid growth of digital services has led to a widespread deployment of opto-electronics that furnish the Internet as an efficient communication backbone. The electroabsorption-modulated laser (EML) is a representative example of a monolithic integrated electro-optic converter that has early become a commodity: it has been widely adopted in telecommunication networks in virtue of its cost- and energy-efficient light generation and modulation. This study reviews the state-of-the-art of EML applications. Despite its simplicity, the EML addresses numerous use cases that require either the transmission or the reception of optical signals, such as equaliser-free high-bandwidth intensity modulation/direct-detection links at low signal drive, analogue signal transmission with high signal integrity, spectral sculpting for dispersion-tolerant transmission and vector modulation. Full-duplex transceiver functionality in lieu of a pair of dedicated half-duplex sub-systems is eventually attained by combining transmission and reception. This strategy of significantly reducing the cost for a bidirectional communication engine will be discussed for coherent digital data and analogue radio-over-fibre transmission and optical ranging. The maturity of EMLs as coherent transceivers will be evidenced by a small penalty for realising full-duplex transmission and the accomplishment of homodyne detection, which obviates digital signal processing for the purpose of signal recovery.