Evarist Palushani

Bio: Evarist Palushani is an academic researcher from University of Copenhagen. The author has contributed to research in topics: Wavelength-division multiplexing & Multiplexing. The author has an hindex of 10, co-authored 51 publications receiving 635 citations. Previous affiliations of Evarist Palushani include Technical University of Denmark.

Transmission of Single-Channel 16-QAM Data Signals at Terabaud Symbol Rates

Abstract: We present latest results for OTDM transmission systems in combination with digital coherent detection achieving record-high serial data rates in a single-wavelength channel. We show serial data transmission of 5.1 Tb/s (640 GBd) over 80-km and 10.2 Tb/s (1.28 TBd) over 29-km dispersion managed fiber (DMF). For 5.1-Tb/s transmission over 80-km DMF, the BER of all 128 OTDM-tributaries (both polarizations) is found to be below the hard-decision FEC-threshold, corresponding to an error-free net data rate of 4.8 Tb/s. In a 10.2-Tb/s experiment, the BER of all 256 TDM-tributaries (both polarizations) is found to be below the FEC-threshold in the back-to-back configuration. This translates to an error-free net data rate of 9.5 Tb/s. After transmission over a 29-km DMF negligible pulse broadening and a BER below the FEC limit is found.

640 Gbit/s and 1.28 Tbit/s polarisation insensitive all optical wavelength conversion

Abstract: We report the first demonstration of polarisation insensitive all-optical wavelength conversion (AOWC) for single wavelength channel 640 Gbit/s return-to-zero differential-phase-shift-keying (RZ-DPSK) signal and 1.28 Tbit/s polarisation multiplexed (Pol-Mux) RZ-DPSK signals using a 100-m polarisation-maintaining highly nonlinear fiber (PM-HNLF) in a polarisation diversity loop configuration. The AOWC is based on four-wave mixing in PM-HNLF. Error free performance is achieved for the wavelength converted signals. Less than 0.5 dB polarisation sensitivity is obtained.

Single wavelength channel 10.2 Tb/s TDM-data capacity using 16-QAM and coherent detection

Abstract: We present a serial 10.2-Tb/s transmission-system using a 1.28-TBd RZ-16-QAM signal, polarization multiplexing and ultra-fast coherent demultiplexing. Considering FEC-overhead, we achieve a record error-free net data rate of 9.5-Tb/s and transmission over 29-km.

OTDM-to-WDM Conversion Based on Time-to-Frequency Mapping by Time-Domain Optical Fourier Transformation

Abstract: This paper reports on the utilization of the time-domain optical Fourier transformation (OFT) technique for serial-to-parallel conversion of optical time division multiplexed (OTDM) data tributaries into dense wavelength division multiplexed (DWDM) channels. The OFT is implemented by using a dispersive medium followed by phase modulation; the latter being achieved by a four-wave mixing process with linearly chirped pump pulses. Both numerical and experimental investigations of the OTDM-to-WDM conversion technique are carried out. Experimental validations are performed on 320- and 640-Gbit/s OTDM data with error-free performance.

Switching characteristics of an InP photonic crystal nanocavity: experiment and theory.

Abstract: The dynamical properties of an InP photonic crystal nanocavity are experimentally investigated using pump-probe techniques and compared to simulations based on coupled-mode theory. Excellent agreement between experimental results and simulations is obtained when employing a rate equation model containing three time constants, that we interpret as the effects of fast carrier diffusion from an initially localized carrier distribution and the slower effects of surface recombination and bulk recombination. The variation of the time constants with parameters characterizing the nanocavity structure is investigated. The model is further extended to evaluate the importance of the fast and slow carrier relaxation processes in relation to patterning effects in the device, as exemplified by the case of all-optical wavelength conversion.

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.

High-capacity millimetre-wave communications with orbital angular momentum multiplexing

Abstract: One property of electromagnetic waves that has been recently explored is the ability to multiplex multiple beams, such that each beam has a unique helical phase front. The amount of phase front ‘twisting’ indicates the orbital angular momentum state number, and beams with different orbital angular momentum are orthogonal. Such orbital angular momentum based multiplexing can potentially increase the system capacity and spectral efficiency of millimetre-wave wireless communication links with a single aperture pair by transmitting multiple coaxial data streams. Here we demonstrate a 32-Gbit s−1 millimetre-wave link over 2.5 metres with a spectral efficiency of ~16 bit s−1 Hz−1 using four independent orbital–angular momentum beams on each of two polarizations. All eight orbital angular momentum channels are recovered with bit-error rates below 3.8 × 10−3. In addition, we demonstrate a millimetre-wave orbital angular momentum mode demultiplexer to demultiplex four orbital angular momentum channels with crosstalk less than −12.5 dB and show an 8-Gbit s−1 link containing two orbital angular momentum beams on each of two polarizations. High speed data transmission using orbital angular momentum beams has been recently demonstrated. Here, Yan et al. demonstrate a 32 Gbit/s millimetre-wave communication link using eight coaxially propagating independent orbital angular momentum beams with four orbital angular momentum states on two orthogonal polarizations.

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.

Self-configuring universal linear optical component

Abstract: We show how to design an optical device that can perform any linear function or coupling between inputs and outputs. This design method is progressive, requiring no global optimization. We also show how the device can configure itself progressively, avoiding design calculations and allowing the device to stabilize itself against drifts in component properties and to continually adjust itself to changing conditions. This self-configuration operates by training with the desired pairs of orthogonal input and output functions, using sets of detectors and local feedback loops to set individual optical elements within the device, with no global feedback or multiparameter optimization required. Simple mappings, such as spatial mode conversions and polarization control, can be implemented using standard planar integrated optics. In the spirit of a universal machine, we show that other linear operations, including frequency and time mappings, as well as nonreciprocal operation, are possible in principle, even if very challenging in practice, thus proving there is at least one constructive design for any conceivable linear optical component; such a universal device can also be self-configuring. This approach is general for linear waves, and could be applied to microwaves, acoustics, and quantum mechanical superpositions. © 2013 Chinese Laser Press OCIS codes: (220.1080) Active or adaptive optics; (130.6750) Systems; (230.3120) Integrated optics devices.

Self-configuring universal linear optical component [Invited]

Abstract: We show how to design an optical device that can perform any linear function or coupling between inputs and outputs. This design method is progressive, requiring no global optimization. We also show how the device can configure itself progressively, avoiding design calculations and allowing the device to stabilize itself against drifts in component properties and to continually adjust itself to changing conditions. This self-configuration operates by training with the desired pairs of orthogonal input and output functions, using sets of detectors and local feedback loops to set individual optical elements within the device, with no global feedback or multiparameter optimization required. Simple mappings, such as spatial mode conversions and polarization control, can be implemented using standard planar integrated optics. In the spirit of a universal machine, we show that other linear operations, including frequency and time mappings, as well as nonreciprocal operation, are possible in principle, even if very challenging in practice, thus proving there is at least one constructive design for any conceivable linear optical component; such a universal device can also be self-configuring. This approach is general for linear waves, and could be applied to microwaves, acoustics, and quantum mechanical superpositions.