Wavelength tunable receiver for FSK modulated optical signals based on standard direct-detection circuitry

1995 ◽  
Author(s):  
P. van Eijk ◽  
J. G. Jennen ◽  
Antonius A. Koonen
Keyword(s):  
Direct Detection ◽  
Optical Signals ◽  
Wavelength Tunable ◽  
Tunable Receiver

scholarly journals Accurate Power-Efficient Format-Scalable Multi-Parallel Optical Digital-to-Analogue Conversion

Photonics ◽  
2021 ◽  
Vol 8 (2) ◽  
pp. 38
Author(s):  
Moshe Nazarathy ◽  
Ioannis Tomkos
Keyword(s):  
Energy Efficiency ◽  
Direct Detection ◽  
Coherent Detection ◽  
Performance Limits ◽  
Optical Modulators ◽  
Analog To Digital ◽  
Power Efficient ◽  
Optical Signals ◽  
Digital To Analog Converters ◽  
Optical Analog

In optical transmitters generating multi-level constellations, optical modulators are preceded by Electronic Digital-to-Analog-Converters (eDAC). It is advantageous to use eDAC-free Optical Analog to Digital Converters (oDAC) to directly convert digital bitstreams into multilevel PAM/QAM optical signals. State-of-the-art oDACs are based on Segmented Mach-Zehnder-Modulators (SEMZM) using multiple modulation segments strung along the MZM waveguides to serially accumulate binary-modulated optical phases. Here we aim to assess performance limits of the Serial oDACs (SEMZM) and introduce an alternative improved Multi-Parallel oDAC (MPoDAC) architecture, in particular based on arraying multiple binary-driven MZMs in parallel: Multi-parallel MZM (MPMZM) oDAC. We develop generic methodologies of oDAC specification and optimization encompassing both SEMZM and MPMZM options in Direct-Detection (DD) and Coherent-Detection (COH) implementations. We quantify and compare intrinsic performance limits of the various serial/parallel DD/COH subclasses for general constellation orders, comparing with the scant prior-work on the multi-parallel option. A key finding: COH-MPMZM is the only class synthesizing ‘perfect’ (equi-spaced max-full-scale) constellations while maximizing energy-efficiency-SEMZM/MPMZM for DD are less accurate when maximal energy-efficiency is required. In particular, we introduce multiple variants of PAM4|8 DD and QAM16|64 COH MPMZMs, working out their accuracy vs. energy-efficiency-and-complexity tradeoffs, establishing their format-reconfigurability (format-flexible switching of constellation order and/or DD/COH).

scholarly journals Amplify-and-Forward Based Cascaded RF-UWOC System

2019 ◽  
Vol 8 (2) ◽  
pp. 5573-5577
Keyword(s):  
High Speed ◽  
Direct Detection ◽  
Thermal Fluctuations ◽  
Underwater Acoustic Communication ◽  
Radio Link ◽  
Air Bubbles ◽  
Optical Turbulence ◽  
Amplify And Forward ◽  
Optical Signals ◽  
Wireless Optical Communication

A cascaded radio frequency-underwater wireless optical communication (RF-UWOC) system using an amplifyand-forward relay is considered. UWOC supports high speed communication for underwater surveillance, monitoring of climate change, and different deep-sea mining activities making it a s suitable substitute to underwater acoustic communication. The proposed fixed-gain AF based cascaded radio-optical system can connect underwater with land. The system comprises of Nakagami-m faded radio link and mixture ExponentialGeneralized Gamma (EGG) faded UWOC link. Salinity, air bubbles, and thermal fluctuations in water causes underwater optical turbulence (UOT). Optical signals are modulated by subcarrier intensity modulation technique at the relay and heterodyne or direct detection is performed at destination. For this proposed communication system, outage and error analyses are carried out. It is observed that the performance of the considered system deteriorates more because of the underwater optical turbulence (UOT) due to thermal fluctuations and air bubbles as compared to UOT introduced by salinity.

SEMICONDUCTOR WAVELENGTH TUNABLE OPTICAL FILTERS

1993 ◽  
Vol 02 (04) ◽  
pp. 643-659 ◽  
Author(s):  
T. NUMAI
Keyword(s):  
Wavelength Division Multiplexing ◽  
Direct Detection ◽  
Optical Filters ◽  
Switching Systems ◽  
Switching Speed ◽  
Photonic Switching ◽  
Detection Scheme ◽  
Wavelength Division ◽  
Wavelength Tunable ◽  
Tunable Optical Filters

Wavelength-division multiplexing (WDM) lightwave transmission systems and wavelength-division (WD) photonic switching systems are attractive for improvement in line capacity for lightwave telecommunication services, because they utilize a huge wavelength (frequency) domain as signal channels. Wavelength tunable optical filters are key devices for these WDM and WD systems in direct detection scheme. In particular, semiconductor wavelength tunable optical filters are suitable for monolithic integration with photonic devices such as semiconductor lasers, switches and detectors. Also, the switching speed of wavelength is faster than that of other optical filters. This paper briefly summarizes the state-of-the-art semiconductor wavelength tunable optical filters and their applications to WD photonic switching systems.

Detection and Characterization of earth-like Planets

1997 ◽  
Vol 161 ◽  
pp. 299-311 ◽  
Author(s):  
Jean Marie Mariotti ◽  
Alain Léger ◽  
Bertrand Mennesson ◽  
Marc Ollivier
Keyword(s):  
Direct Detection ◽  
Contrast Ratio ◽  
Angular Size ◽  
Physical Nature ◽  
Major Axis ◽  
Infrared Emission ◽  
Space Technology ◽  
Semi Major Axis ◽  
Earth Like Planets ◽  
Visible Wavelengths

AbstractIndirect methods of detection of exo-planets (by radial velocity, astrometry, occultations,...) have revealed recently the first cases of exo-planets, and will in the near future expand our knowledge of these systems. They will provide statistical informations on the dynamical parameters: semi-major axis, eccentricities, inclinations,... But the physical nature of these planets will remain mostly unknown. Only for the larger ones (exo-Jupiters), an estimate of the mass will be accessible. To characterize in more details Earth-like exo-planets, direct detection (i.e., direct observation of photons from the planet) is required. This is a much more challenging observational program. The exo-planets are extremely faint with respect to their star: the contrast ratio is about 10−10at visible wavelengths. Also the angular size of the apparent orbit is small, typically 0.1 second of arc. While the first point calls for observations in the infrared (where the contrast goes up to 10−7) and with a coronograph, the latter implies using an interferometer. Several space projects combining these techniques have been recently proposed. They aim at surveying a few hundreds of nearby single solar-like stars in search for Earth-like planets, and at performing a low resolution spectroscopic analysis of their infrared emission in order to reveal the presence in the atmosphere of the planet of CO H2O and O3. The latter is a good tracer of the presence of oxygen which could be, like on our Earth, released by biological activity. Although extremely ambitious, these projects could be realized using space technology either already available or in development for others missions. They could be built and launched during the first decades on the next century.

A novel enzyme immunoassay for the direct detection of H. pylori antigens in stool

2001 ◽  
Vol 120 (5) ◽  
pp. A492-A493 ◽  
Author(s):  
E HAINDL ◽  
H BENESCH ◽  
A FINCK ◽  
V MUEHISTEIN ◽  
A LEODOLTER ◽  
...  
Keyword(s):  
Enzyme Immunoassay ◽  
Direct Detection ◽  
H Pylori
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