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Resonant modulators encode electrical data onto wavelength-multiplexed optical carriers. Today, silicon microring modulators are perceived as promising to implement such links; however, they provide limited bandwidth and need thermal stabilization systems. Here we present plasmonic micro-racetrack modulators as a potential successor of silicon microrings: they are equally compact and compatible with complementary-metal–oxide–semiconductor-level driving voltages, but offer electro-optical bandwidths of 176 GHz, a 28 times improved stability against operating temperature changes and no self-heating effects. The temperature-resistant organic electro-optic material enables operation at 85 °C device temperature. We show intensity-modulated transmission of up to 408 Gbps at 12.3 femtojoules per bit with a single resonant modulator. Plasmonic micro-racetrack modulators offer a solution to encode high data rates (for example, the 1.6 Tbps envisioned by next-generation communications links) at a small footprint, with low power consumption and marginal, if no, temperature control., Nature Photonics, 17 (4), ISSN:1749-4885, ISSN:1749-4893

A method for reducing the training time of a deep learning based digital backpropagation (DL-DBP) is presented. The method is based on dividing a link into smaller sections. A smaller section is then compensated by the DL-DBP algorithm and the same trained model is then reapplied to the subsequent sections. We show in a 32 GBd 16QAM 2400 km 5-channel wavelength division multiplexing transmission link experiment that the proposed stacked DL-DBPs provides a 0.41 dB gain with respect to linear compensation scheme. This needs to be compared with a 0.56 dB gain achieved by a non-stacked DL-DBPs compensated scheme for the price of a 203% increase in total training time. Furthermore, it is shown that by only training the last section of the stacked DL-DBP, one can increase the compensation performance to 0.48 dB., IEEE Photonics Technology Letters, 34 (7), ISSN:1041-1135, ISSN:1941-0174

A transparent Optical-subTHz-Optical link providing record-high single line rates of 240 Gbit/s and 192 Gbit/s on a single optical carrier over distances from 5 to 115 m is demonstrated. Besides a direct mapping of the optical to a 230 GHz subTHz-carrier frequency by means of a uni-traveling carrier (UTC) photodiode, we demonstrate direct conversion of data from the subTHz domain back to the optical domain by a plasmonic modulator. It is shown that the subTHz-to-optical upconversion can even be performed at good quality without any electrical amplifiers. Finally, at the receiver, the local oscillator is employed to directly map the optical signal back to the electrical baseband within a coherent receiver., Journal of Lightwave Technology, 40 (6), ISSN:0733-8724, ISSN:1558-2213

The first transparent Optical-subTHz-Optical link providing record-high line-rates of 240 and 190 Gbit/s over distances from 5 to 115 m was recently demonstrated. The link has been based on a direct data-conversion from optical to subTHz using a > 500 GHz plasmonic Mach-Zehnder modulator. We discuss the potential of plasmonic devices in subTHz wireless links to efficiently bridge optical fiber networks, Proceedings of SPIE, 12027, ISSN:0277-786X, Metro and Data Center Optical Networks and Short-Reach Links V

OOK line rates of 220 Gbit/s and 408 Gbit/s 8PAM and transmission over 100 m are demonstrated with a resonant plasmonic racetrack modulator. The device requires low 0.6 Vp driver voltages, offers a bandwidth >110 GHz and on-chip losses of 1.0 dB., 2021 European Conference on Optical Communication (ECOC), ISBN:978-1-6654-3868-1, ISBN:978-1-6654-1150-9

A computationally efficient deep learning based digital backpropagation (DL-DBP) algorithm providing a 1.9 dB SNR over a conventional linear compensation (chromatic dispersion compensation algorithm) and a 1 dB gain over a conventional back-propagation algorithm of the same complexity is presented. The algorithm has been tested in a 1200km transmission experiment. Also, if the algorithm is tested against a conventional digital backpropagation algorithm with the gain, then the new algorithm requires a factor 6 lower complexity. We discuss its training procedure and its principle. We discuss its training procedure and its principle. ISSN:0277-786X

Metallic grating couplers can be extremely broadband and efficient. In this work, we investigate an all-plasmonic fiber-to-chip coupler with a coupling efficiency of -2.7 dB and an optical 3-dB passband of 300 nm.

The first transparent Optical-THz-Optical link providing record-high line-rates up to 240 and 190 Gbit/s over distances from 5 to 115m is demonstrated. The link is based on direct data-conversion from optical to sub-THz and vice-versa.

We present a plasmonic platform featuring efficient, broadband metallic fiber-to-chip couplers that directly interface plasmonic slot waveguides, such as compact and high-speed electro-optic modulators. The metallic gratings exhibit an experimental fiber-to-slot coupling efficiency of −2.7 dB with −1.4 dB in simulations with the same coupling principle. Further, they offer a huge spectral window with a 3 dB passband of 350 nm. The technology relies on a vertically arranged layer stack, metal–insulator–metal waveguides, and fiber-to-slot couplers and is formed in only one lithography step with a minimum feature size of 250 nm. As an application example, we fabricate new modulator devices with an electro-optic organic material in the slot waveguide and reach 50 and 100 Gbit/s data modulation in the O- and C-bands within the same device. The devices’ broad spectral bandwidth and their relaxed fabrication may render them suitable for experiments and applications in the scope of sensing, nonlinear optics, or telecommunications., Nano Letters, 21 (11), ISSN:1530-6984, ISSN:1530-6992

A deep learning (DL) based digital backpropagation (DBP) method with a 1 dB SNR gain over a conventional 1 step per span DBP is demonstrated in a 32 GBd 16QAM transmission across 1200 km. The new DL-DPB is shown to require 6 times less computational power over the conventional DBP scheme. The achievement is possible due to a novel training method in which the DL-DBP is blind to timing error, state of polarization rotation, frequency offset and phase offset. An analysis of the underlying mechanism is given. The applied method first undoes the dispersion, compensates for nonlinear effects in a distributed fashion and reduces the out of band nonlinear modulation due to compensation of the nonlinearities by having a low pass characteristic. We also show that it is sufficient to update the elements of the DL network using a signal with high nonlinearity when dispersion or nonlinearity conditions changes. Lastly, simulation results indicate that the proposed scheme is suitable to deal with impairments from transmission over longer distances. © 2020 Optical Society of America. ISSN:1094-4087

An ultra-compact 3D memristive atomic switch is co-integrated with a field-effect transistor (FET). The combined devices outperform similar state-of-the-art arrangements. The integrated transistor operates with an extremely sharp switching slope of below 3 mV/dec, low leakage below pA and a high current on/off ratio Ion/Ioff < 106. Moreover, our atomic switch features a < 10 ns switching and a < 300 mV operating voltage. Most importantly, the atomic switch has a small footprint of < 10 nm by 10 nm in line with the extreme feature size of the current FET technologies. Thus, this design could addresses the future needs of integrated circuits (ICs) for high integration density at low power consumption.

OSA Technical Digest, Advanced Photonics 2018 (BGPP, IPR, NP, NOMA, Sensors, Networks, SPPCom, SOF), ISBN:978-1-943580-43-9

We demonstrate an efficient multi-format real-time Nyquist-FDM receiver implemented on a single FPGA. The single-polarization receiver uses an oversampling of 8/7 to detect a 28 GBd signal with four subcarriers transmitted over 300 km SSMF.

Demonstration of a real-time receiver working with 28 GBd at 32 GSa/s. The signal processing is done on a single FPGA. The resource-saving non-integer oversampling of 8/7 is enabled by a timing synchronization in the frequency domain.

A blind frequency and phase search algorithm for joint frequency and phase recovery is introduced. The algorithm achieves low complexity due to processing in polar coordinates, which reduces the amount of multiplications. We show an implementation for real-time processing at 32 GBd on FPGA hardware. The hardware design allows for dynamic multi-format operation, where the format can be switched flexibly after each clock cycle (250 MHz, 128 Symbols) between 4QAM, 8QAM, and 16QAM. The performance of the algorithm is evaluated with respect to laser phase noise, carrier frequency offset, and carrier frequency offset drift. The effect of working with limited hardware resources is investigated. An FPGA implementation shows the feasibility of our carrier recovery algorithm with a negligible penalty when compared to a floating point simulation., Optics Express, 24 (22), ISSN:1094-4087

Low power broadband plasmonic silicon-photonic racetrack modulators are introduced. 100 Gbit/s NRZ-OOK and 100 Gbit/s 4-PAM direct detection is demonstrated. The devices feature a bandwidth of 50 GHz, operate with 1.3 V p and are of interest because of the low on-chip loss characteristics., 2020 European Conference on Optical Communications (ECOC), ISBN:978-1-7281-7361-0, ISBN:978-1-7281-7362-7

A plasmonic modulator spanning both C- and O-band for dual-band data modulation up to 100 Gbit/s in one single device is presented. Fiber-to-fiber insertion loss can be as low as 11 dB. (C) 2020 The Author(s)

We demonstrate an efficient multi-format real-time Nyquist-FDM receiver implemented on a single FPGA. The single-polarization receiver with only 8/7 oversampling receives 56 Gbit/s 4QAM and 112 Gbit/s 16QAM transmitted over 300 km SSMF.

Data centers require optical interconnect solutions that are highly scalable with respect to the channel count, the bit rates and the power consumption. Plasmonics offers smallest footprints, operates up to highest speed, requires little driver circuitry and thus meets many of the DCI requirements.

We introduce efficient polarization-insensitive SiN O-band grating coupler relying on a simple fabrication procedure. It’s an essential but missing building block in photonics and needed, for example, to realize detectors for light with unknown polarization., OSA Technical Digest, Optica Advanced Photonics Congress 2022, ISBN:978-1-957171-16-6

We propose and demonstrate a new low-complexity hardware architecture and digital signal processing (DSP) implementation for coherent reception of Nyquist frequency division multiplexed (Nyquist-FDM, digital subcarrier multiplexing) signals in real time. Key to achieve lowest complexity is the combination of an optimized frequency domain and time domain processing block. In the frequency domain processing, we combine subcarrier equalization and timing recovery with a noninteger oversampling ratio of 16/15. In the time domain, we take advantage of polar coordinate processing for the carrier recovery to avoid complex multiplications. The receiver is optimized for flexible operation and allows the adaption of filter coefficients and modulation format between 4QAM, hybrid 4/16QAM, and 16QAM within one clock cycle. The efficiency of the DSP is demonstrated by a real-time coherent receiver implementation on a single FPGA and is experimentally evaluated. Despite of the limited hardware resources, the receiver can detect a 30 GBd Nyquist-FDM signal with four subcarriers and a net data rate of 60 Gb/s (4QAM), 90 Gb/s (4/16QAM), or 120 Gb/s (16QAM) sampled with 32 GSa/s and demodulate one of the subcarriers at a time. Transmission of 300 km through standard single mode fiber is demonstrated with a BER below the soft-decision forward error correction limit.