Phys.org August 8, 2023 Orbital angular momentum (OAM) spectrum diagnosis is a fundamental building block for diverse OAM-based systems. Among others, the simple on-axis interferometric measurement can retrieve the amplitude and phase information of complex OAM spectra in a few shots. Yet, its single-shot retrieval remains elusive, due to the signal–signal beat interference inherent in the measurement. Researchers in Switzerland have introduced the concept of Kramers–Kronig (KK) receiver in coherent communications to the OAM domain, enabling rigorous, single-shot OAM spectrum measurement. They explained in detail the working principle and the requirement of the KK method and applied the technique to […]
Category Archives: Communications technology
Lights could be the future of the internet and data transmission
Phys.org July 25, 2023 The modulation characteristics of perovskite LEDs are not clear. An international team of researchers (UK, Switzerland) has developed a new approach for realizing fast perovskite photonic sources on silicon based on tailoring alkylammonium cations in perovskite systems. They showed the recombination behaviour of charged species at various carrier density regimes relevant for their modulation performance. By integrating a Fabry–Pérot microcavity on silicon, they demonstrated perovskite devices with efficient light outcoupling and achieved device modulation bandwidths of up to 42.6 MHz and data rates above 50 Mbps, with further analysis suggesting that the bandwidth may exceed gigahertz levels. According […]
Protecting light communication with random objects
Phys.org July 17, 2023 Researchers in the Netherlands have developed an optical communication system with two scattering layers to hide both the sender and receiver, by measuring the correlation of the intermediate speckle generated between the two layers. The binary message is modulated as spatially shaped wavefronts, and the high number of transmission modes of the scattering layers allowed for many uncorrelated incident wavefronts to send the same message, making it difficult for an attacker to intercept or decode the message and thus increasing secrecy. They collected 50,000 intermediate speckle patterns and analyzed their correlation distribution using the Kolmogorov-Smirnov (K-S) […]
China has begun launching its own satellite internet network
Phys.org July 17, 2023 On Sunday, July 9, launched a prototype internet satellite from China’s Jiuquan Satellite Launch Center in Inner Mongolia. The satellite will conduct several tests to validate the broadband satellite technology. The long-term aim of the project is to create a constellation of 13,000 satellites code-named “Guo Wang”. They intend to create two constellations (GW-A59 and GW-2) with a coverage of 37.5 to 42.5 GHz (space-to-Earth) and 47.2 to 51.4 GHz (Earth-to-space). According to multiple sources, this constellation is part of a wider effort by China to stake its claim to the growing satellite internet market. The […]
Photonic filter separates signals from noise to support future 6G wireless communication
Science Daily April 11, 2023 To achieve high reconfigurability in integrated microwave photonic filters (IMPFs) previous works adopt complicated system structures and modulation formats, which put great pressure on power consumption and controlment, and, therefore, impeded the massive deployment of IMPF. Researchers in China proposed a streamlined architecture for a wideband and highly reconfigurable IMPF on the silicon photonics platform. For various practical filter responses, to avoid complex auxiliary devices and bias drift problems, a phase-modulated flexible sideband cancellation method was employed based on the intensity-consistent single-stage-adjustable cascaded-microring. The IMPF exhibited an operation band extending to millimeter-wave and other extraordinary […]
Scientists develop energy-saving, tunable meta-devices for high-precision, secure 6G communications
Nanowerk March 16, 2023 Researchers in Hong Kong has invented a synthetic phase design of rotary doublet Airy beam and triplet Gaussian beam varifocal meta-devices to fully control the terahertz beam’s propagation direction and coverage area. The focusing spot can be delivered to arbitrary positions in a two-dimensional plane or a three-dimensional space. The highly concentrated signal can be delivered to a specific position, and the transmission direction can be adjusted freely to enable secure, flexible, and high-directivity 6G communication systems. According to the researchers this technology avoids the high costs associated with extensive use of active components. 6G communication […]
New method enables effective free-space optical communication regardless of weather
Phys.org March 1, 2023 To overcome the barriers to light propagation for free-space optical communication (FSO) a team of researchers in the US (Rensselaer Polytechnic Institute, University of Michigan) proposed making use of the acoustic properties of a laser filament coupled together with a donut-shaped signal beam. A filament generated by an ultrafast laser was accompanied by an acoustic wave that clears a cylindrical chamber around the filament’s plasma column that can mimic a transmission channel. They presented a method to couple a Laguerre–Gauss beam through the obstacle-free channel. They imaged and measured the transmitted signal carried by the structured […]
New photodiode with extremely low excess noise for optical communication and long-range LIDAR
Phys.org February 9, 2023 Avalanche photodiodes (APDs) have internal gain, which means that when compared to PIN-photodiodes they typically have a higher signal-to-noise ratio. Researchers in the UK designed and demonstrated photodiode that exhibits high multiplication factor with very little added noise. The new semiconductor alloy is based on a GaAsSb absorption region that has excellent detection efficiency at infrared wavelengths (up to 1,700 nanometers). The device incorporated an appropriate doping profile to suppress tunneling current from the absorption region, achieving a large avalanche gain, ∼130 at room temperature. It exhibits extremely low excess noise factors of 1.52 and 2.48 […]
Signal processing algorithms improved turbulence in free-space optic tests
Science Daily December 20, 2022 Researchers in the UK used commercially available photonic lanterns, a commercial transponder, and a spatial light modulator to emulate turbulence. They simultaneously transmitted multiple data signals using different spatially shaped beams of light using a photonic lantern. By detecting light with these shapes using a second lantern, more of the light is collected at the receiver, and the original data can be unscrambled greatly reduce the impact of the atmosphere on the quality of the data received in MIMO digital signal processing. By transmitting multiple beams of different shapes through the same telescopes and detecting […]
New communications technology: Super-fast optical lasers
Science Daily November 9, 2022 While enabling orders-of-magnitude gains in data rates, optical signals impose much stricter pointing requirements and are strongly affected by atmospheric turbulence. Researchers in Australia established a coherent 1550 nm link across turbulent atmosphere between a deployable optical terminal and a drone-mounted retroreflector. Through 10 Hz machine vision optical tracking with nested 200 Hz tip/tilt adaptive optics stabilisation, they corrected for pointing errors and atmospheric turbulence to maintain robust single mode fiber coupling, resulting in an uninterrupted 100 Gbps optical data link while tracking at angular rates of up to 1.5 deg/s, equivalent to that of […]