KEYWORDS: Deep ultraviolet, Light emitting diodes, Wireless communications, Signal to noise ratio, Sun, Signal attenuation, Lighting standards, Light sources and illumination, Interference (communication), Epitaxy
Since the intensity of deep ultraviolet (DUV) light with the wavelength below 300 nm is nearly zero in the sun spectrum, optical wireless communications (OWC) based on DUV light can have a unique “zero-background” characteristics. We recently demonstrated LED-based DUV OWC at 280-nm band over a 1.5-m direct line-of-site channel realizing the effective data rate of as fast as >2 Gbps under standard room lighting and >1 Gbps under direct sun with outdoor experiments. These experiments were performed off-the-shell DUV AlGaN light-emitting diodes, which was grown by metalorganic vapor-phase epitaxy using an AlN/sapphire template with dense macrosteps.
High-speed optical wireless communication (OWC) systems based on light-emitting diode (LED), such as Li-Fi, are promising solutions for the looming spectrum crisis in 6G wireless communications. OWCs typically extend the RF spectrum by harnessing the visible light and infrared spectra, but the recent advancements in deep-ultraviolet (DUV) LED device technology allow us to further extend the OWC spectrum down to the DUV range, namely the solar-blind band. This talk reviews the recent progress of the high-speed OWCs based on DUV-LEDs including Gbps-class transmission demonstrations in direct sunlight and analyses on the microscopic structural and optical characteristics of high-speed AlGaN-based LEDs.
High-capacity fiber-optic communications are promising technologies to satisfy people’s continuously growing demands for bandwidth hungry data services. Multi-wavelength optical circuit switching (OCS) technology is already widely deployed, however, with the limited number of transceivers equipped at each optical node and other constraints, the number of lightpaths which can be established and employed simultaneously in an optical network is restricted. This reduces the utilization efficiency of wavelength resources. Comparing to OCS, dynamic optical switching systems such as optical packet switching (OPS) offer higher efficiency in terms of wavelength resource utilization and have the potential to share more of the wavelength resources on fiber-links between larger numbers of users simultaneously. In such networks, bursty input signals or changes in traffic density may cause optical power surges that can damage optical components or impose gain transients on the signals that impair signal quality. A common approach for reducing gain transients is to employ electrical automatic gain control (AGC) or optical gain-clamping by optical feedback (OFB). AGC may be limited by the speed of the feedback circuit and result in additional transients. Meanwhile OFB can clamp the gain of power varying optical signals without transient but can introduce amplitude fluctuations caused by relaxation oscillations in the lasing cavity for large input power fluctuations. We propose and demonstrate a novel scheme for suppressing the power transients and the relaxation oscillations. This scheme can be utilized in optical amplifiers even if the optical feedback is employed.
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