Quantum-dash laser diode for millimeter wave over fiber transmission: A potential technology for next-generation access networks

Photonic generation of microwave, millimeter or Terahertz wave signals have been garnering a great deal of attention in the recent years due what they offer to the table in several applications such as radio-over-fiber systems, wireless communications, which forms the backbone of the present information technology. With respect to traditional electronic means, photonic generation of these signals excels in different aspects including cost, size, power consumption, and most importantly, wide range of tunability. In literature, different methodologies have been adopted to realize photonic generation of microwave, millimeter (MMW) and Terahertz (THz) waves such as optical fiber and semiconductor lasers, optical amplifiers, and photonic laser. However, achieving these radio-frequency (RF) signal via optical mean pose several challenges on the light source, which require to be highly stable, coherent, and exhibiting low phase noise. Hence, these key requirements necessitates considering different active region light sources as RF transmitters and receivers, which forms the backbone of the mobile networks and optical access networks in general. In this research work, we aim to investigate the generation of MMW via optical means from a new class of InAs/InP quantum-dash based active region semiconductor laser emitting in L-band. Quantum-dash (Qdash) nanostructures has already shown tremendous potential as light sources in high bit rate wavelength division multiplexed systems and passive optical networks. The inherent wide gain profile offered by these nanostructures, which covers CLU communication bands, has been exploited to demonstrate broadband lasers and optical amplifiers, for ease in integration with the existing optical networks. Besides, high performance dynamic characteristics compared to the quantum-well (Qwell) lasers counterpart, has emerged from these quantum-dot (Qdot) and quantum-wire (Qwire) like nanostructure based lasers. Hence, this study we set a goal to further reinforce potential employment of InAs/InP Qdash laser for MMW generator, enabling tens of Giga-bits-per-second transmission at the end user either using wireless or fiber or fiber-wireless channels. Moreover, other advantages, such as small-foot print and possibility of mass deployment, offered by this device, as a results of potential wideband MMW tunability, would qualify this novel generator as a next generation access network transmitter, to cater the requirements of the future information technology. The laser diode is InAs/InP Qdash active region based wherein the barrier layer thickness is chirped, and would be employed along with other optical passive components to generate MMW via injection locking technique. In particular, various configurations of MMW generator, for instance, dual injection locking, would be tested for stability, high power and side mode suppression ratio (SMSR). Next, the system would be modified to tune the generated beat-tone between the two locked modes, thereby realizing a wideband tunable MMW generator. Later, the generated MMW would be deployed in transmission experiments via single mode fiber (SMF) and characterized in terms of eye diagram, received bit-error-rate, etc. Through this proposed work we would like to set a platform for the researchers to appreciate the benefits offered by quantum-dash nanostructure based devices and enable them to design efficient transmitter and receiver systems for next generation optical access networks. Apart from the research contents, the project also aims at strengthening Photonics research, particularly in the field of optoelectronic devices, in the department of Electrical Engineering (EE), King Fahd University of Petroleum and Minerals (KFUPM). This will facilitates the undergraduate/graduate students to appreciate the field of Photonics and also reinforce the department and KFUPM research competency in both, accommodating other research projects, and training students for fast growing job market of the important technological field of Photonics in Saudi Arabia.