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We demonstrate wireless transmission of QPSK signals at a carrier frequency of 0.3 THz using a generalized Kramers-Kronig receiver with a Schottky barrier diode. We achieve a line rate of 100 Gbit/s over a transmission distance of 110 m.

We analyze the performance of the Kramers-Kronig receiver in a DWDM transmission system. We find that for a symbol rate of 32 GBd an optical filter bandwidth of less than 50 GHz is required to keep beat-noise penalties low.

We report a THz wireless link at 0.2885 THz which is embedded in a photonic network. An ultra-broadBand plasmonic modulator directly converts the THz signal to the optical domain. We transmit QPSK data with line rates up to 50 Gbit/s.

We show coherent wireless transmission at carrier frequencies within 0.30+0.02 THz using up to 20 QPSK-modulated subcarriers with a symbol rate of 0.75 GBd each, leading to an aggregate line rate of 30 Gbit/s. We exploit optoelectronic techniques, both for THz generation and coherent reception.

Additive fabrication on the nanoscale lends itself to in-situ structuring of 3D single-mode waveguides and free-form coupling elements directly at the facets of optical fibers or photonic integrated circuits. We give an overview of our recent progress in fabricating photonic wire bonds and printed microlenses by direct-write two-photon lithography. These techniques offer new perspectives for a wide variety of applications, ranging from advanced photonic transceiver modules to highly efficient astrophotonic systems.

We demonstrate a robust concept for instantaneous extraction of fringe order and unwrapped phase in integrated Mach-Zehnder sensors without continuous tracking. The scheme exploits a frequency-modulated probe laser and a 2×3 MMI at the sensor output and allows for continuous self-calibration and high-resolution phase detection.

We demonstrate a four-channel hybrid multi-chip module comprising InP lasers, silicon-organic hybrid (SOH) modulators, and single-mode fibers, all connected via photonic wire bonds. We transmit 56 GBd QPSK and 16QAM signals at a total data rate of 784 Gbit/s over 75 km.

Silicon-plasmonic photodetection based on internal photoemission exploits the intrinsic absorption in plasmonic waveguides at metal-dielectric interfaces. For this purpose we designed an asymmetric metal-semiconductor-metal waveguide with a width of 75 nm. Our plasmonic internal photoemission detector (PIPED) shows a rec-ord-high photocurrent sensitivity of up to S = 0.12 A / W for light at a wavelength of 1550 nm. The opto-electronic bandwidth is extremely large and allows data reception at rates of at least 40 Gbit/s. As another appli-cation, photomixing of two different optical carriers incident on the PIPED generates photocurrents with THz-frequencies, which can be used for short-range wireless communication. Finally, because in contrast to ordinary pin-photodetectors the sensitivity S(U) depends on the voltage U across the device, a PIPED can be employed for all-optical heterodyne reception and down-conversion of data on a THz carrier.

We review fabrication and optics of polymeric high-Q whispering gallery mode resonators. They are employed as bio-sensors featuring selective parallel functionalization of arrays and integration into lab-on-a-chip systems. Liquid crystalline elastomers enable wide tunability of resonances. Elastomer substrates allow photonic molecules with tunable coupling gap.

Advanced wavelength-division multiplex-ing (WDM) requires both efficient multi-wavelength light sources to generate optical carriers and highly scalable photonic-electronic interfaces to encode data on these carriers. In this paper, we give an overview on our recent progress regarding silicon-organic hy-brid (SOH) integration and comb-based WDM transmission.

InAs/ InP quantum dash based mode locked lasers are particularly suited for frequency comb generation. Multi-terabit/s data transmission has been achieved using one single chip.

Limitations of silicon photonics can be overcome by hybrid integration of silicon photonic or plasmonic circuits with organic materials or by photonic multi-chip systems. We give an overview on our recent progress regarding both silicon-organic hybrid (SOH) integration and multi-chip integration enabled by photonic wire bonding.

We investigate super-channel intradyne reception using an optical frequency comb as local oscillator (LO). We synchronize its center frequency and free spectral range with the corresponding parameters of the transmitter comb to compensate environmental drifts during operation.

We demonstrate a silicon-organic hybrid (SOH) Mach-Zehnder modulator suitable for 100 Gbit/s on-off keying (OOK) with peak-to-peak drive voltages of 1.4 V and energy consumption below 100 fJ/bit. Devices were fabricated using standard processes on a commercial silicon photonic platform.

We show that undoped silicon waveguides may suffer of up to 1.8dB/cm free-carrier absorption caused by improper surface passivation, this result opens new perspectives for low-loss silicon photonics and high-speed gateless devices.

Silicon-organic hybrid (SOH) integration combines silicon photonic devices with electro-optic organic cladding materials. We demonstrate that SOH modulators can be used to generate advanced modulation formats with high symbol rates at low operating voltages and low energy consumption. Moreover, we show that the SOH approach can be extended to plasmonic waveguide structures, leading to the plasmonic-organic hybrid (POH) concept.

By comparison to a stable reference laser, the phase noise of a frequency comb from a quantum-dash mode-locked laser can be compensated. The quality of the resulting carriers allows the transmission of data at a rate of 1 Tbit/s in a single polarization over a distance of 75 km using a standard forward error correction.

Silicon photonics offers tremendous potential for inexpensive high-yield photonic-electronic integration by enabling fabless fabrication and joint processing of photonic and electronic circuitry. Besides conventional dielectric waveguides, plasmonic structures can also be efficiently realized on the silicon photonic platform, thereby reducing the device footprint by more than an order of magnitude. Silicon and metals, however, fall short of certain optical properties that are indispensable for high-performance photonic devices. In particular, neither material exhibits an appreciable second-order optical nonlinearity, thereby making efficient electro-optic modulators challenging.

We demonstrate, to the best of our knowledge, the first real-time single-carrier frequency division multiple access transmitter designed to be used in photonic communication networks. It is capable of providing 10 Gbit/s net bitrate at 3.125 GHz slot bandwidth, providing data to nine quasi-Nyquist spectral groups. The transmitter is designed with respect to logic efficiency and a fine user grid allowing the operation of narrow bandwidth, low-cost optical network units. Moreover, it offers runtime flexibility, an efficient 96-point discrete Fourier transform and a multiplier-free differential phase encoder. The article concludes with a presentation of the transmitters hardware setup and an evaluation of its performance in the case of direct electrical AWG-ONU Rx interconnection and the optical back-to-back case.

We demonstrate 16QAM and QPSK modulation at symbol rates of 40 GBd and 45 GBd using a silicon-based IQ modulator. The device enables data rates up to 160 Gbit/s in a single polarization with an estimated energy consumption of 120fJ/bit.

We demonstrate generation and transmission of QPSK and 16QAM signals by directly interfacing highly efficient silicon-organic hybrid (SOH) modulators to GTH ports of an FPGA. Peak-to-peak voltages amount to only 0.41 V-pp. Neither digital-to-analog converters (DAC) nor drive amplifiers are required.

High-speed optical interconnects rely on advanced wavelength-division multiplexing (WDM) schemes. However, while photonic-electronic interfaces can be efficiently realized on silicon-on-insulator chips, dense integration of the corresponding light sources still represents a major challenge. Chip-scale frequency comb sources present an attractive alternative for providing a multitude of optical carriers for WDM transmission. In this paper, we give an overview on our recent progress towards terabit communications with chip-scale frequency comb sources. In a first set of experiments, we demonstrate frequency comb generation based on silicon-organic hybrid (SOH) electro-optic modulators, enabling transmission data rates of up to 1.152 Tbit/s. A second set of experiments demonstrates Kerr comb generation in nonlinear integrated microcavities, leading to data rates of up to 1.44 Tbit/s. Our experiments demonstrate that frequency comb generation in chip-scale devices represents a viable approach to terabit/s communications.

We demonstrate a phase shifter based on a silicon slot waveguide infiltrated with liquid crystal. We achieve a phase shift of 73 pi for a 5V drive voltage, with a voltage-length product of 0.022V.mm around 1V. We can drive the phase shifter directly with a 1V, duobinary pulse-width-modulated signal, allowing direct digital CMOS control of an analog optical phase shifter.

We give an overview on our recent achievements in the field of SOH integration, covering in-device electro-optic coefficients r 33 in excess of 200 pm/V, highly efficient Mach-Zehnder modulators, IQ modulators, and modulator-based frequency comb generators

Silicon photonics offers tremendous potential for inexpensive high-yield photonic-electronic integration by enabling fabless fabrication and joint processing of photonic and electronic circuitry. Silicon as an optical material, however, falls short of certain properties that are indispensable for high-performance devices. In particular, bulk silicon does not feature any second-order optical nonlinearity due to crystal symmetry, thereby making efficient electro-optic modulators challenging. These deficiencies can be overcome by silicon-organic hybrid (SOH) integration, which combines silicon-on-insulator (SOI) waveguides with electro-optic organic materials. We give an overview on our recent progress in the field of SOH modulators, covering highly efficient devices with energy consumptions of a few femtojoule per bit and modulator-based frequency comb generators that enable WDM data transmission at terabit/s data rates.

High carrier frequencies in the terahertz range 0.1...30 THz are required for wireless data transmission at line rates at or beyond 100 Gbit/s. Here we demonstrate a system with one to three carriers near 237 GHz for (75...100) Gbit/s single-polarization transmission over distances of (20...40) m. The narrow-band THz carrier is generated by photomixing of highly stable mode-locked laser lines in a uni-travelling-carrier photodiode. The electrical photodiode output is radiated over a lensed horn antenna. Besides a receiving lensed horn antenna, the receiver comprises monolithic integrated circuits with mixers and amplifiers. This synergetic use of THz photonics and electronics (“teratronics”) should be scalable to wireless Tbit/s transmission over 1 km. Such a wireless link could bridge the last mile to a subscriber, or could connect two spatially separated fibre gateways.

Silicon-organic hybrid (SOH) integration can extend the capabilities of silicon photonics by combining silicon-on-insulator (SOI) waveguides with functional organic cladding materials. This enables energy-efficient electro-optic modulators and ultra-compact phase shifters. We review recent progress in SOH integration, discussing both fundamental device concepts and experimental demonstrations.

The GALACTICO technology platform combines GaAs modulator technology, Silicon board and Germanium receiver technology with 130nm BiCMOS technology. The paper will review the present status of our work, providing an overview of all technological building blocks and system performance.

We report on a blind polarization demultiplexing algorithm for arbitrarily shaped complex-modulated signals. The technique evaluates sums of moduli of the received complex-valued electric field, is computationally very efficient, and thus suited for real-time applications. Prior to polarisation demultiplexing neither data demodula-tion nor timing or carrier recovery is required. Our procedure combines the numerical simplicity of the constant modulus algorithm with the versatility of the Stokes space approach. Experiments confirm our findings.

The introduction of advanced optical modulation formats for coherent data transmission and multilevel signalling enlarges the transmission capacities but also requires more complex opto-electronic components. The need for cost efficient compact solutions is the main driver for photonic-electronic integration technologies. In the framework of the European Project GALACTICO a new mixed technology platform for advanced transceivers is being developed. The technology relies on the cost efficient Germanium-on-Silicon technology, and SiGe BiCMOS technology together with GaAs technology [1]. A selection of the best suited materials and solutions ready to deploy is made to provide the performance required for transmitter and receiver of next generation networks operated at capacities beyond Terabit/s.

Silicon modulators fabricated by scalable, established CMOS technology, promise an answer to today's power consumption challenges. With advanced modulation formats and the resulting higher spectral efficiencies, long-haul applications for silicon modulators come into reach. Energy efficient, high speed modulators were demonstrated as resonant [1] and non-resonant [2] devices. A single-carrier single-polarization data rate of 56 Gbit/s is considered state-of-the-art [3]. Usually, free-carrier dispersion is exploited in silicon modulators.

We review the Nyquist sync-shaped multiplexing technique to generate Terabit/s super channels. This technique has recently allowed the transmission of signals with 18 bit/s/Hz, and has enabled single laser transmission of 32 Tbit/s.

Measuring the quality of optical signals is one of the most important tasks in optical communications. A variety of metrics are available, namely the general shape of the eye diagram, the optical signal-to-noise power ratio (OSNR), the Q-factor as a measure of the eye opening, the error vector magnitude (EVM) that is especially suited for quadrature amplitude modulation (QAM) formats, and the bit error ratio (BER). While the BER is the most conclusive quality determinant, it is sometimes difficult to quantify, especially for simulations and off-line processing. We compare various metrics analytically, by simulation, and through experiments. We further discuss BER estimates derived from OSNR, Q-factor and EVM data and compare them to measurements employing six modulation formats at symbol rates of 20 GBd and 25 GBd, which were generated by a software-defined transmitter. We conclude that for optical channels with additive Gaussian noise the EVM metric is a reliable quality measure. For nondata-aided reception, BER below 0.01 can be estimated from measured EVM.

We investigate the performance of a fiber-based OFDM transmission system for wireless backhauling with a target data rate of 2.5…10 Gbit/s using directly modulated lasers. Newly developed semiconductor DFB lasers in index and complex coupled curved stripe technology as well as lasers with ridge waveguide resonators were experimentally characterized and found to be suitable for direct modulation at the required data rates. Based on measured data, we implemented a numerical laser model and studied by simulation the limits and the optimum operating conditions of an optical OFDM network for wireless backhauling.

Low-loss photonic wire bonds (PWB) enable inter-chip connections with average losses of 1.6 dB in the whole C-band. The underlying technique allows for flexible automatic fabrication of single-mode chip-to-chip interconnects.

In this paper, the chip-to-chip interconnection architecture adopted by the EU-project NAVOLCHI are discussed. The plasmonic physical layer consisting of a plasmonic nanoscale laser, a modulator, an amplifier and a detector is introduced. Current statuses of the plasmonic devices are reviewed.

Photonic wire bonds (PWB) enable single-mode chip-to-chip interconnects that are suitable for mass production. We demonstrate for the first time a single-mode PWB link between two different nanophotonic silicon-on-insulator chips.

Silicon nanophotonics is considered a key enabler of future photonic-electronic information processing systems. Driven by substantial research investments, photonic integration on silicon-on-insulator (SOI) substrates has reached a degree of maturity that already permits industrial adoption. Silicon-organic hybrid integration (SOH) is a viable extension of the SOI material system for efficient electro-optic modulation and ultrafast all-optical signal processing.

Ways to minimize the footprint of electro-optical modulators are discussed. We first review state-of-the art silicon modulators and then examine novel plasmonic modulator concepts that show promise to enable ultrafast switching with devices in the micron-scale range.

Progress in electronic data processing enables software-defined optical (SDO) transmission. Modulation formats and symbol rates are set by software-controlled field programmable gate arrays (FPGA). We demonstrate a real-time SDO transmitter for 8 modulation formats, which can be swapped in 5 ns. Single-polarization 64QAM symbol generation at 28 GBd allows transmitting 168 Gbit/s real-time data. We further present a 101.5 Gbit/s single-polarization OFDM transmitter based on real-time FPGA processing, where we modulate 58 subcarriers with 16QAM data. For terabit OFDM reception, optical pre-processing is required to demultiplex high-bitrate signals down to lower-bitrate tributaries, which then can be processed digitally. We discuss a 10.8 Tbit/s receiver employing an all-optical fast Fourier transform to demultiplex 75 optical subcarriers modulated with 16QAM-formated symbols at a rate of 16 GBd.

A 40 Gbit/s electro-optic modulator is demonstrated. The modulator is based on a slotted silicon waveguide filled with an organic material. The silicon organic hybrid (SOH) approach allows combining highly nonlinear electro-optic organic materials with CMOS-compatible silicon photonics technology.

Future RoF systems will be integrated into PON. We demonstrate that SOA reach extender provide a large optical and electrical power dynamic range of 30 dB. Optimum conditions are determined for QPSK and 16-QAM RF signals.

Two selected applications of semiconductor optical amplifiers (SOA) are discussed, namely linear in-line amplification in gigabit passive optical networks and fast nonlinear all-optical signal processing. We report on measurements demonstrating the suitability of quantum-dot (QD) and bulk SOA for the respective application areas. For in-line amplification the saturation power of the SOA should be large, while it has to be low for efficient signal processing. For bulk SOA we find by physically-based simulations that at large injection currents and for a fixed gain, p-doping (n-doping) of the active layer increases (decreases) the saturation power. Recently published experiments show that qualitatively these results carry over to QD-SOA.