Remote Photonic THz Generation Using an Optical Frequency Comb and Multicore Fiber

[EN] This paper proposes and demonstrates a photonic THz generation technique based on an optical frequency comb and multicore fiber (MCF) transmission, with the advantage of remote generation with great reconfigurability and reduced digital signal processing (DSP). The feasibility of the proposed technique is evaluated experimentally comparing the performance when transmitting a data wavelength and a local oscillator for optical heterodyning over a single core or over different cores in a 1-km MCF link. The proposed remote photonic THz generation technique is demonstrated employing a 16QAM 12.5 GBd signal. A short wireless transmission at 183 GHz center frequency with 0.25 m antenna-separation is achieved after 1 km MCF, meeting the soft-decision decision forward error correction (SD-FEC) bit error rate (BER) recommendation of 2 center dot 10(-2). The analysis includes the received photocurrent range for which the BER meets the standard hard-decision forward error correction (HD-FEC) recommendation of 3.8 center dot 10(-3) BER. The BER performance is analyzed considering different DSP configurations, with and without frequency offset estimation (FOE) and decision-driven least mean squares (DD LMS) equalization. The performance of the remote photonic THz generation technique is evaluated comparatively against traditional free-running laser transmission over MCF, confirming the advantage of using comb generation to reduce the frequency offset fluctuation and simplify the DSP.This work was supported by Spanish State Research Agency under Grants PID2019-106163RJ-I00/AEI/10.13039/501100011033 MULTICORE+ and MINECO/FEDER UE RTI2018-101296-B-I00 MULTI-BEAM5G projects, in part by the European Union'sHorizon 2020 Research and Innovation Programme underGrant H2020-EU.2.1.1.-762119 ULTRAWAVE, and in part by the Engineering and Physical Sciences Research Council under Grant EPSRC EP/P003990/1 COALESCE. The work of Maria Morant supported by Generalitat Valenciana under Grant BEST/2019/047.Morant, M.; González-Guerrero, L.; Renaud, CC.; Llorente, R. (2021). Remote Photonic THz Generation Using an Optical Frequency Comb and Multicore Fiber. Journal of Lightwave Technology. 39(24):7621-7627. https://doi.org/10.1109/JLT.2021.311508476217627392

InP integrated optical frequency comb generator using an amplified recirculating loop

A novel realisation of photonically integrated optical frequency comb generation is demonstrated on indium phosphide (InP) using a generic foundry platform. The architecture, based on the amplified recirculating loop technique, consists of cascaded electro-optic phase modulators embedded within a short waveguide loop. While an injected continuous wave laser signal is recirculated by the loop, the modulators are driven with a modulation frequency corresponding to the round-trip loop length frequency. This results in many phase coherent, evenly spaced optical comb lines being generated. The choice of InP as an integration platform allows immediate optical amplification of the modulated signal by embedded semiconductor optical amplifiers, enabling loop losses to be compensated and expanding the comb across broad optical bandwidths. This approach reduces the requirement for external, high-power optical amplifiers, improving the compactness and power efficiency of the full system. The system was modelled to identify off-resonance behaviour, outlining limits in matching both the modulation frequency and seed laser frequency to the round-trip loop frequency for optimal comb line generation to be achieved. The experimental device occupied a fraction of the 6 x 2 mm2 InP chip and operated at round-trip loop frequencies of 6.71 GHz to produce 59 comb lines within a 20 dB power envelope. All comb lines exhibited strong phase coherence as characterised by low composite phase noise measurements of -105 dBc/Hz at 100 kHz. A second device is also presented with a shorter loop length operating at ~10 GHz which generated 57 comb lines. Both loop configurations included short waveguide phase shifters providing a degree of tunability of the free spectral range with a tuning range of 150 MHz for small injection currents of less than 2.5 mA.This research work has been supported by the UK Engineering and Physical Sciences Research Council (EPSRC) through the Integrated Photonics and Electronic Systems (IPES) Centre of Doctoral Training and PICSat project (EPSRC Reference: EP/S000976/1)

High performance waveguide uni-travelling carrier photodiode grown by solid source molecular beam epitaxy

The first waveguide coupled phosphide-based UTC photodiodes grown by Solid Source Molecular Beam Epitaxy (SSMBE) are reported in this paper. Metal Organic Vapour Phase Epitaxy (MOVPE) and Gas Source MBE (GSMBE) have long been the predominant growth techniques for the production of high quality InGaAsP materials. The use of SSMBE overcomes the major issue associated with the unintentional diffusion of zinc in MOVPE and gives the benefit of the superior control provided by MBE growth techniques without the costs and the risks of handling toxic gases of GSMBE. The UTC epitaxial structure contains a 300 nm n-InP collection layer and a 300 nm n++-InGaAsP waveguide layer. UTC-PDs integrated with Coplanar Waveguides (CPW) exhibit 3 dB bandwidth greater than 65 GHz and output RF power of 1.1 dBm at 100 GHz. We also demonstrate accurate prediction of the absolute level of power radiated by our antenna integrated UTCs, between 200 GHz and 260 GHz, using 3d full-wave modelling and taking the UTC-to-antenna impedance match into account. Further, we present the first optical 3d full-wave modelling of waveguide UTCs, which provides a detailed insight into the coupling between a lensed optical fibre and the UTC chip.Comment: 19 pages, 24 figure

Pilot-tone assisted 16-QAM photonic wireless bridge operating at 250 GHz

A photonic wireless bridge operating at a carrier frequency of 250 GHz is proposed and demonstrated. To mitigate the phase noise of the free-running lasers present in such a link, the tone-assisted carrier recovery is used. Compared to the blind phase noise compensation (PNC) algorithm, this technique exhibited penalties of 0.15 dB and 0.46 dB when used with aggregated Lorentzian linewidths of 28 kHz and 359 kHz, respectively, and 20 GBd 16-quadrature amplitude modulation (QAM) signals. The wireless bridge is also demonstrated in a wavelength division multiplexing (WDM) scenario, where 5 optical channels are generated and sent to the Tx remote antenna unit (RAU). In this configuration, the full band from 224 GHz to 294 GHz is used. Finally, a 50 Gbit/s transmission is achieved with the proposed wireless bridge in single channel configuration. The wireless transmission distance is limited to 10 cm due to the low power emitted by the uni-travelling carrier photodiode used in the experiments. However, link budget calculations based on state-of-the-art THz technology show that distances >1000 m can be achieved with this approach.Comment: 13 pages, in Journal of Lightwave Technolog

Coherent terahertz photonics

We present a review of recent developments in THz coherent systems based on photonic local oscillators. We show that such techniques can enable the creation of highly coherent, thus highly sensitive, systems for frequencies ranging from 100 GHz to 5 THz, within an energy efficient integrated platform. We suggest that such systems could enable the THz spectrum to realize its full applications potential. To demonstrate how photonics-enabled THz systems can be realized, we review the performance of key components, show recent demonstrations of integrated platforms, and give examples of applications

Evolutionary Trends of the Pharyngeal Dentition in Cypriniformes (Actinopterygii: Ostariophysi)

International audienceBACKGROUND: The fish order Cypriniformes is one of the most diverse ray-finned fish groups in the world with more than 3000 recognized species. Cypriniformes are characterized by a striking distribution of their dentition: namely the absence of oral teeth and presence of pharyngeal teeth on the last gill arch (fifth ceratobranchial). Despite this limited localisation, the diversity of tooth patterns in Cypriniformes is astonishing. Here we provide a further description of this diversity using X-ray microtomography and we map the resulting dental characters on a phylogenetic tree to explore evolutionary trends. RESULTS: We performed a pilot survey of dental formulae and individual tooth shapes in 34 adult species of Cypriniformes by X-ray microtomography (using either conventional X-ray machine, or synchrotron microtomography when necessary) or by dissecting. By mapping morphological results in a phylogenetic tree, it emerges that the two super-families Cobitoidea and Cyprinoidea have followed two distinct evolutionary pathways. Furthermore, our analysis supports the hypothesis of a three-row dentition as ancestral for Cyprinoidea and a general trend in tooth row reduction in most derived lineages. Yet, this general scheme must be considered with caution as several events of tooth row gain and loss have occurred during evolutionary history of Cyprinoidea. SIGNIFICANCE: Dentition diversity in Cypriniformes constitutes an excellent model to study the evolution of complex morphological structures. This morphological survey clearly advocates for extending the use of X-ray microtomography to study tooth morphology in Cypriniformes. Yet, our survey also underlines that improved knowledge of Cypriniformes life traits, such as feeding habits, is required as current knowledge is not sufficient to conclude on the link between diet and dental morphology

The 2017 Terahertz Science and Technology Roadmap

Science and technologies based on terahertz frequency electromagnetic radiation (100GHz-30THz) have developed rapidly over the last 30 years. For most of the 20th century, terahertz radiation, then referred to as sub-millimeter wave or far-infrared radiation, was mainly utilized by astronomers and some spectroscopists. Following the development of laser based terahertz time-domain spectroscopy in the 1980s and 1990s the field of THz science and technology expanded rapidly, to the extent that it now touches many areas from fundamental science to “real world” applications. For example THz radiation is being used to optimize materials for new solar cells, and may also be a key technology for the next generation of airport security scanners. While the field was emerging it was possible to keep track of all new developments, however now the field has grown so much that it is increasingly difficult to follow the diverse range of new discoveries and applications that are appearing. At this point in time, when the field of THz science and technology is moving from an emerging to a more established and interdisciplinary field, it is apt to present a roadmap to help identify the breadth and future directions of the field. The aim of this roadmap is to present a snapshot of the present state of THz science and technology in 2016, and provide an opinion on the challenges and opportunities that the future holds. To be able to achieve this aim, we have invited a group of international experts to write 17 sections that cover most of the key areas of THz Science and Technology. We hope that The 2016 Roadmap on THz Science and Technology will prove to be a useful resource by providing a wide ranging introduction to the capabilities of THz radiation for those outside or just entering the field as well as providing perspective and breadth for those who are well established. We also feel that this review should serve as a useful guide for government and funding agencies

Incorporating biodiversity responses to land use change scenarios for preventing emerging zoonotic diseases in areas of unknown host-pathogen interactions

The need to reconcile food production, the safeguarding of nature, and the protection of public health is imperative in a world of continuing global change, particularly in the context of risks of emerging zoonotic disease (EZD). In this paper, we explored potential land use strategies to reduce EZD risks using a landscape approach. We focused on strategies for cases where the dynamics of pathogen transmission among species were poorly known and the ideas of “land-use induced spillover” and “landscape immunity” could be used very broadly. We first modeled three different land-use change scenarios in a region of transition between the Cerrado and the Atlantic Forest biodiversity hotspots. The land-use strategies used to build our scenarios reflected different proportions of native vegetation cover, as a proxy of habitat availability. We then evaluated the effects of the proportion of native vegetation cover on the occupancy probability of a group of mammal species and analyzed how the different land-use scenarios might affect the distribution of species in the landscape and thus the risk of EZD. We demonstrate that these approaches can help identify potential future EZD risks, and can thus be used as decision-making tools by stakeholders, with direct implications for improving both environmental and socio-economic outcomes

A Solve-RD ClinVar-based reanalysis of 1522 index cases from ERN-ITHACA reveals common pitfalls and misinterpretations in exome sequencing

Purpose Within the Solve-RD project (https://solve-rd.eu/), the European Reference Network for Intellectual disability, TeleHealth, Autism and Congenital Anomalies aimed to investigate whether a reanalysis of exomes from unsolved cases based on ClinVar annotations could establish additional diagnoses. We present the results of the “ClinVar low-hanging fruit” reanalysis, reasons for the failure of previous analyses, and lessons learned. Methods Data from the first 3576 exomes (1522 probands and 2054 relatives) collected from European Reference Network for Intellectual disability, TeleHealth, Autism and Congenital Anomalies was reanalyzed by the Solve-RD consortium by evaluating for the presence of single-nucleotide variant, and small insertions and deletions already reported as (likely) pathogenic in ClinVar. Variants were filtered according to frequency, genotype, and mode of inheritance and reinterpreted. Results We identified causal variants in 59 cases (3.9%), 50 of them also raised by other approaches and 9 leading to new diagnoses, highlighting interpretation challenges: variants in genes not known to be involved in human disease at the time of the first analysis, misleading genotypes, or variants undetected by local pipelines (variants in off-target regions, low quality filters, low allelic balance, or high frequency). Conclusion The “ClinVar low-hanging fruit” analysis represents an effective, fast, and easy approach to recover causal variants from exome sequencing data, herewith contributing to the reduction of the diagnostic deadlock