S. Koenig

Bio: S. Koenig is an academic researcher from Infinera. The author has contributed to research in topics: Quadrature amplitude modulation & Optical amplifier. The author has an hindex of 15, co-authored 40 publications receiving 2524 citations. Previous affiliations of S. Koenig include Siemens & Karlsruhe Institute of Technology.

Wireless sub-THz communication system with high data rate

Abstract: A wireless communication system with a maximum data rate of 100 Gbit s−1 over 20 m is demonstrated using a carrier frequency of 237.5 GHz. The photonic schemes used to generate the signal carrier and local oscillator are described, as is the fast photodetector used as a mixer for data extraction.

26 Tbit s-1 line-rate super-channel transmission utilizing all-optical fast Fourier transform processing

Abstract: Optical transmission systems with terabit per second (Tbit s-1) single-channel line rates no longer seem to be too far-fetched. New services such as cloud computing, three-dimensional high-definition television and virtual-reality applications require unprecedented optical channel bandwidths. These high-capacity optical channels, however, are fed from lower-bitrate signals. The question then is whether the lower-bitrate tributary information can viably, energy-efficiently and effortlessly be encoded to and extracted from terabit per second data streams. We demonstrate an optical fast Fourier transform scheme that provides the necessary computing power to encode lower-bitrate tributaries into 10.8 and 26.0 Tbit s-1 line-rate orthogonal frequency division multiplexing (OFDM) data streams and to decode them from fibre-transmitted OFDM data streams. Experiments show the feasibility and ease of handling terabit per second data with low energy consumption. To the best of our knowledge, this is the largest line rate ever encoded onto a single light source.

Error Vector Magnitude as a Performance Measure for Advanced Modulation Formats

Abstract: We examine the relation between optical signal-to-noise ratio (OSNR), error vector magnitude (EVM), and bit-error ratio (BER). Theoretical results and numerical simulations are compared to measured values of OSNR, EVM, and BER. We conclude that the EVM is an appropriate metric for optical channels limited by additive white Gaussian noise. Results are supported by experiments with six modulation formats at symbol rates of 20 and 25 GBd generated by a software-defined transmitter.

Wireless sub-THz communication system with high data rate enabled by RF photonics and active MMIC technology

Abstract: In communications, the frequency range 0.1–30 THz is essentially terra incognita. Recently, research has focused on this terahertz gap, because the high carrier frequencies promise unprecedented channel capacities1. Indeed, data rates of 100 Gbit s were predicted2 for 2015. Here, we present, for the first time, a single-input and single-output wireless communication system at 237.5 GHz for transmitting data over 20 m at a data rate of 100 Gbit s. This breakthrough results from combining terahertz photonics and electronics, whereby a narrow-band terahertz carrier is photonically generated by mixing comb lines of a mode-locked laser in a uni-travellingcarrier photodiode. The uni-travelling-carrier photodiode output is then radiated over a beam-focusing antenna. The signal is received by a millimetre-wave monolithic integrated circuit comprising novel terahertz mixers and amplifiers. We believe that this approach provides a path to scale wireless communications to Tbit s rates over distances of >1 km. Data rates in both fibre-optic and wireless communications have been increasing exponentially over recent decades. For the upcoming decade this trend seems to be unbroken, at least as far as fibreoptic communications is concerned. In wireless communications, however, the spectral resources are extremely limited because of the heavy use of today’s conventional frequency range up to 60 GHz. Even with spectrally highly efficient quadrature amplitude modulation (QAM) and the spatial diversity achieved with multipleinput and multiple-output (MIMO) technology, a significant capacity enhancement to multi-gigabit or even terabit wireless transmission requires larger bandwidths, which are only available in the high millimetre-wave and terahertz region. Between 200 and 300 GHz there is a transmission window with low atmospheric losses3. In contrast to free-space optical links, millimetre-wave or terahertz transmission is much less affected by adverse weather conditions like rain and fog4,5. Here, we present for the first time a single-input single-output (SISO) wireless 100 Gbit s link with a carrier frequency of 237.5 GHz. By combining state-of-the-art terahertz photonics and electronics and by utilizing the large frequency range in the terahertz window between 200 and 300 GHz, we realize a wireless 100 Gbit s link with SISO technology, that is, a link with one transmit antenna and one receive antenna. To date, 100 Gbit s wireless links have only been demonstrated at lower carrier frequencies around 100 GHz (refs 6–8) over a wireless distance of 1 m, with a bit error ratio (BER) of 1 × 10. Because of the limited bandwidth, these systems relied on optical polarization multiplexing and spatial MIMO with more than one wireless transmitter and receiver. Here, a 100 Gbit s wireless transmission capacity is achieved without resorting to MIMO technology. We envisage various applications1,9,10 for such a high-capacity wireless link (Fig. 1). If an end-to-end fibre connection is absent and the deployment of a new fibre link is not economical, as might be the case in difficult-to-access terrains and certain rural areas (last mile problem), or if an already existing fibre connection fails, a permanent or ad hoc wireless connection could help. Furthermore, we anticipate indoor applications, such as highspeed wireless data transfers between mobile terminals and desktop computers. Figure 1 presents a schematic of our 100 Gbit s wireless experiment embedded into an application scenario where an obstacle, here a broad river, is bridged by the wireless link. We first discuss the general system concept, and then provide further details. For the transmitter (Tx) we use a terahertz photonics technology set-up (Fig. 1). We generate exceptionally pure and stable terahertz carriers by heterodyning frequency-locked laser lines11. A control unit contains a single mode-locked laser (MLL), selects the appropriate frequency-locked comb lines, and modulates data on the carrier lines. An optical fibre transmits the modulated carriers together with an unmodulated comb line, which acts as a remote local oscillator (LO), to a remote uni-travelling-carrier photodiode (UTC-PD). By photomixing the LO and the modulated carriers, radiofrequency signals are generated. Optical heterodyning has already been used in earlier works to implement multi-gigabit wireless systems in the 60 GHz band12–14, in the W-band (75–110 GHz, refs 6–8,15,16), at 120 GHz (refs 17,18) and at carrier frequencies beyond 200 GHz (refs 19,20). For the electronic in-phase/quadrature (IQ) receiver (Rx), we use a custom-developed, active millimetre-wave monolithic integrated circuit (MMIC) with a radiofrequency bandwidth of 35 GHz (refs 21,22). This is, to the best of our knowledge, the first active broadband IQ mixer at 237.5 GHz. The Rx comprises a low-noise amplifier (LNA) and a subharmonic downconversion IQ mixer, and is realized in a metamorphic high electron mobility transistor (mHEMT) technology (Supplementary Section S5) featuring a gate length of 35 nm and a cutoff frequency of more than 900 GHz (refs 23,24). The complex data are directly downconverted to the baseband and separated into I and Q signals. Previous works6–8 in the W-band have illustrated the importance of a high carrier frequency. However, to date, no direct downconversion to baseband has been used due to a lack of IQ mixers covering the full W-band. For carrier frequencies beyond 110 GHz (refs 17–20), simple on–off keying modulation and envelope

Femtojoule electro-optic modulation using a silicon–organic hybrid device

Abstract: Energy-efficient electro-optic modulators are at the heart of short-reach optical interconnects, and silicon photonics is considered the leading technology for realizing such devices. However, the performance of all-silicon devices is limited by intrinsic material properties. In particular, the absence of linear electro-optic effects in silicon renders the integration of energy-efficient photonic–electronic interfaces challenging. Silicon–organic hybrid (SOH) integration can overcome these limitations by combining nanophotonic silicon waveguides with organic cladding materials, thereby offering the prospect of designing optical properties by molecular engineering. In this paper, we demonstrate an SOH Mach–Zehnder modulator with unprecedented efficiency: the 1-mm-long device consumes only 0.7 fJ bit−1 to generate a 12.5 Gbit s−1 data stream with a bit-error ratio below the threshold for hard-decision forward-error correction. This power consumption represents the lowest value demonstrated for a non-resonant Mach–Zehnder modulator in any material system. It is enabled by a novel class of organic electro-optic materials that are designed for high chromophore density and enhanced molecular orientation. The device features an electro-optic coefficient of r33≈180 pm V−1 and can be operated at data rates of up to 40 Gbit s−1. Scientists have demonstrated a hybrid silicon–organic electro-optic modulator that consumes just 0.7 fJ of energy per processed data bit. Such highly energy efficient optical modulators are needed for the short-reach, high-density data interconnects of the future. The 1-mm-long device is based on a Mach–Zehnder interferometer design and is compatible with data rates of up to 40 Gbit s−1. The modulator realizes a subfemtojoule efficiency by employing silicon slot waveguides filled with a highly nonlinear organic material called DLD164, which has a very large electro-optic coefficient of 180 pm V−1. The researchers, who are from Europe, the USA and China, claim that the modulator has the lowest power consumption demonstrated to date for a non-resonant Mach–Zehnder modulator realized in any material system.

Terabit free-space data transmission employing orbital angular momentum multiplexing

Abstract: Researchers demonstrate the ability to multiplex and transfer data between twisted beams of light with different amounts of orbital angular momentum — a development that provides new opportunities for increasing the data capacity of free-space optical communications links.

Integrated lithium niobate electro-optic modulators operating at CMOS-compatible voltages

Abstract: Electro-optic modulators translate high-speed electronic signals into the optical domain and are critical components in modern telecommunication networks1,2 and microwave-photonic systems3,4. They are also expected to be building blocks for emerging applications such as quantum photonics5,6 and non-reciprocal optics7,8. All of these applications require chip-scale electro-optic modulators that operate at voltages compatible with complementary metal–oxide–semiconductor (CMOS) technology, have ultra-high electro-optic bandwidths and feature very low optical losses. Integrated modulator platforms based on materials such as silicon, indium phosphide or polymers have not yet been able to meet these requirements simultaneously because of the intrinsic limitations of the materials used. On the other hand, lithium niobate electro-optic modulators, the workhorse of the optoelectronic industry for decades9, have been challenging to integrate on-chip because of difficulties in microstructuring lithium niobate. The current generation of lithium niobate modulators are bulky, expensive, limited in bandwidth and require high drive voltages, and thus are unable to reach the full potential of the material. Here we overcome these limitations and demonstrate monolithically integrated lithium niobate electro-optic modulators that feature a CMOS-compatible drive voltage, support data rates up to 210 gigabits per second and show an on-chip optical loss of less than 0.5 decibels. We achieve this by engineering the microwave and photonic circuits to achieve high electro-optical efficiencies, ultra-low optical losses and group-velocity matching simultaneously. Our scalable modulator devices could provide cost-effective, low-power and ultra-high-speed solutions for next-generation optical communication networks and microwave photonic systems. Furthermore, our approach could lead to large-scale ultra-low-loss photonic circuits that are reconfigurable on a picosecond timescale, enabling a wide range of quantum and classical applications5,10,11 including feed-forward photonic quantum computation. Chip-scale lithium niobate electro-optic modulators that rapidly convert electrical to optical signals and use CMOS-compatible voltages could prove useful in optical communication networks, microwave photonic systems and photonic computation.

Wireless Communications and Applications Above 100 GHz: Opportunities and Challenges for 6G and Beyond

Abstract: Frequencies from 100 GHz to 3 THz are promising bands for the next generation of wireless communication systems because of the wide swaths of unused and unexplored spectrum. These frequencies also offer the potential for revolutionary applications that will be made possible by new thinking, and advances in devices, circuits, software, signal processing, and systems. This paper describes many of the technical challenges and opportunities for wireless communication and sensing applications above 100 GHz, and presents a number of promising discoveries, novel approaches, and recent results that will aid in the development and implementation of the sixth generation (6G) of wireless networks, and beyond. This paper shows recent regulatory and standard body rulings that are anticipating wireless products and services above 100 GHz and illustrates the viability of wireless cognition, hyper-accurate position location, sensing, and imaging. This paper also presents approaches and results that show how long distance mobile communications will be supported to above 800 GHz since the antenna gains are able to overcome air-induced attenuation, and present methods that reduce the computational complexity and simplify the signal processing used in adaptive antenna arrays, by exploiting the Special Theory of Relativity to create a cone of silence in over-sampled antenna arrays that improve performance for digital phased array antennas. Also, new results that give insights into power efficient beam steering algorithms, and new propagation and partition loss models above 100 GHz are given, and promising imaging, array processing, and position location results are presented. The implementation of spatial consistency at THz frequencies, an important component of channel modeling that considers minute changes and correlations over space, is also discussed. This paper offers the first in-depth look at the vast applications of THz wireless products and applications and provides approaches for how to reduce power and increase performance across several problem domains, giving early evidence that THz techniques are compelling and available for future wireless communications.

Advances in terahertz communications accelerated by photonics

Abstract: This Review covers the state-of-the-art technologies on photonics-based terahertz communications, which are compared with competing technologies based on electronics and free-space optical communications. Future prospects and challenges are also discussed. Almost 15 years have passed since the initial demonstrations of terahertz (THz) wireless communications were made using both pulsed and continuous waves. THz technologies are attracting great interest and are expected to meet the ever-increasing demand for high-capacity wireless communications. Here, we review the latest trends in THz communications research, focusing on how photonics technologies have played a key role in the development of first-age THz communication systems. We also provide a comparison with other competitive technologies, such as THz transceivers enabled by electronic devices as well as free-space lightwave communications.