Electroabsorption‐modulated laser as optical transmitter and receiver: status and opportunities
Bernhard Schrenk
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.