In this paper we present an interconnect framework for FPGAs based on multi gigabit transceivers (MGTs), typically available in modern reconfigurable devices. The framework provides higher bandwidth while using fewer pins compared to existing approaches based on ordinary FPGA IO pins. Unlike other implementations using MGTs for device interconnection, special care has been taken to achieve high throughput and data integrity while keeping latency, resource usage and protocol overhead very low. From a designers perspective, the introduced FPGA interconnect is used like an ordinary asynchronous FIFO allowing easy integration into existing digital designs with no or only very little modification. Depending on the available MGTs, the bandwidth per connection reaches from 3.125 to 28 GBit/s allowing large amounts of data to be moved quickly between multiple FPGAs. The framework allows the use of optical fibers for the data links. This enables an easy distribution of FPGA networks over hundreds of meters. Thus, the presented approach is not only applicable for multi-FPGA prototyping of complex novel computing architectures but also for large data processing facilities commonly found e.g. nearby detectors of large particle accelerator experiments.

In this paper we present an FPGA based, ultra-high speed OFDMA system which is intended to be used as a bandwidth efficient, advanced modulation format in optical access networks like fiber-to-the-home. The aggregate bandwidth of the network reaches up to 50 GBit/s while handling hundreds of different subscribers, sharing the same optical bandwidth. Compared to other domains using OFDM like e.g. wireless communication, data rates in the multi GBit/s range require very high performance signal processing components at a central office and at the subscribers. With modern FPGA technologies like the Xilinx Virtex-6 family and massive parallelization of the algorithms the necessary processing power can be provided. Besides the OFDMA processing blocks themselves also their connections to a suitable analog front end as well as to data sources and sinks have to be considered. The presented system uses digital-to-analogue (DAC) and analogue-to-digital (ADC) converters with up to 25 GSa/s at the central office and up to 3.125 GSa/s at the subscribers. The connection to data sources and sinks is realized via 10G Ethernet links. The whole system is therefore transparent for Ethernet packets making its integration into existing infrastructure very easy.

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.

In this paper the authors describe a novel system on chip (SoC) that is especially developed for digital signal processing of high-speed orthogonal frequency division multiplexing (OFDM) signals with data rates up to gigabits per second. Besides offering a new degree of freedom for the tradeoff between flexibility and performance during runtime, the modular concept of the SoC also allows a tradeoff between performance and costs during design time. The flexibility to adapt the OFDM system parameters by software enables even system designers without a good knowledge of hardware design to implement high-speed OFDM systems. An example configuration of the architecture was implemented on a Virtex-6 FPGA in order to set up a software-defined OFDM transmitter, achieving data rates of several gigabits per second. The paper closes with implementation and performance results of experiments using the developed transmitter and an optical transmission of the generated OFDM signals.

Reconfigurability of FPGAs is an enabler for many applications. In recent years a lot of different reconfiguration approaches and methodologies were presented, including full and partial reconfiguration of devices. In this paper we present the novel methodology of addiguration for Xilinx Spartan-3 devices. Our proposed methodology exploits special properties of the configuration logic and enables to incrementally configure on top of an existing design already running on an FPGA. This work demonstrates a basic technology that might be exploited for testing scenarios or as an entry vector for attacks on FPGA designs. Prototypical experiments have shown that the addiguration can easily be carried out during runtime of the device and over a standard configuration interface.

Recent advances in electronic data processing allow constructing reconfigurable optical transmitters and receivers, where modulation formats and symbol rates are set by software-controlled field programmable gate arrays (FPGA). We report on such a real-time optical transmitter for 8 modulation formats, which can be swapped in 5 ns without data loss. With single-polarization 64QAM symbols generated at 28 GBd, we transmit data at 168 Gbit/s in real time. A similar arrangement defines a single-polarization orthogonal frequency division multiplexing (OFDM) transmitter for a data rate of 101.5 Gbit/s, where 58 subcarriers are encoded with 16QAM data. With a different software setup, the FPGA realizes an optical 56 Gbit/s transmitter for sinc-shaped so-called Nyquist pulses, the spectrum of which is rectangular having the minimum theoretically achievable bandwidth (suitable for Nyquist wavelength division multiplexing, N-WDM). For terabit OFDM reception, optical pre-processing is required to demultiplex high-bitrate signals down to lower-bitrate tributaries, which then can be processed electronically. We discuss a 10.8 Tbit/s (26 Tbit/s) receiver employing an all-optical fast Fourier transform to demultiplex 75 (325) optical subcarriers modulated with 16QAM-formated symbols at a rate of 18 GBd (10 GBd). Groups with any number of subcarriers can be selected with a simple hardware reconfiguration step.

In this paper we present a novel approach for time and frequency synchronization of ultra-high speed OFDM systems processing over 78 million symbols per second. A possible application domain of such OFDM systems is located in optical access networks like fibre to the home which are expected to become widely used in several years. The communication channel characteristics of a glass fibre posses lower demands to the synchronization algorithms compared to a wireless communication channel because carrier frequencies and phases at the receiver change slower and there are nearly no signal reflections. In order to achieve very high data rates of up to 50 GBit/s the concept introduced in this paper exploits the special channel characteristics of a glass fibre in order to reduce the required processing power. A realisation of this concept was implemented for Xilinx Virtex-6 FPGAs to prove its feasibility with technology available today.

Single-laser 32.5 Tbit/s 16QAM Nyquist-WDM transmission with 325 carriers over 227 km at a net spectral efficiency of 6.4 bit/s/Hz is reported.

This paper describes the design and optimization of an ultra- high speed Digital Down Converter (DDC) for a realization by FPGAs. After explaining the general structure of the Digital Down converter we describe in detail how to implement such a design in order to process a digital, massively parallelized signal. The necessary optimizations to achieve an efficient implementation in state of the art FPGAs are explained and a case study for an FPGA optimized Digital Down Converter design suitable for OFDMA systems is presented. The key components of this DDC are highly parallelized half-band filters which are optimized for Virtex- 6 FPGAs and enable the design to decimate a 6 bit wide input signal with a sample rate of 25 GS/s into a 16 bit 1.5625 GS/s signal while achieving an attenuation of around 35 dB. The results include the resource consumption of the DDC for a Virtex-6 XC6VHX380T FPGA as well as the filter response to a chirp test signal. Index Terms ?? FPGA; DDC; OFDMA; FIR; Decimator.

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.

We demonstrate single-laser 32.5 Tbit/s 16QAM Nyquist wavelength division multiplexing transmission over a total length of 227 km of SMF-28 without optical dispersion compensation. A number of 325 optical carriers is derived from a single laser and encoded with dual-polarization 16QAM data using sinc-shaped Nyquist pulses. As we use no guard bands, the carriers have a spacing of 12.5 GHz equal to the symbol rate or Nyquist bandwidth of the data. We achieve a net spectral efficiency of 6.4 bit/s/Hz using a software-defined transmitter, which generates the electric drive signals for the electro-optic modulator in real time.

In the above titled paper (ibid., vol. 24, no. 1, pp. 61-63, Jan. 1, 2012), equation (4) contains an error. The corrected equation is presented here. Additionally, the paper should include an Appendix, which is presented here.

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,

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.

In this paper we present a parallel, FPGA-based implementation of a 256-point Fast Fourier Transform capable to perform over 78 million transformations per second. Its area of operation is located in the ultra-high speed OFDM communication in optical networks where the FFT algorithm provides the basis of the digital signal processing. The main focus lies on an implementation using as less as possible resources while ensuring the required high performance. However, to allow an adaptation of the core to different applications, a flexible adaptivity of internal bit vector widths was realized.

In this paper we present an optically powered and motorized video camera system. Energy for the camera sensor is supplied by a glass fiber carrying 800 mW of optical power, which the sensor converts back to 320 mW of electrical power. The specific advantage of this arrangement is galvanic isolation and a very high robustness with respect to electromagnetic interference. We demonstrate that sufficient energy can be transmitted for driving an Actel Igloo FPGA, which performs the necessary signal processing. Additionally, with the help of capacitive energy storage, some small actuators can be supplied which move the camera sensor head. The base station of the system, based on a Xilinx Virtex-5 FPGA, holds a LEON-3 based system-on-chip encoding the incoming VGA video stream into Motion-JPEG formatted data in realtime, which may be directly sent to the internet using an Ethernet interface. The prototype has numerous fields of application where it performs much better than stateof-the-art solutions. Most prominent examples are visual sensors in high voltage areas as well as medical endoscopes.

In optically powered networks, glass fibres are used for transmitting optical communication signals as well as optical energy for electrically powered devices. Advantages over existing power delivery technologies are: immunity to electromagnetic interference, spark-free power for safety-critical applications, slim cables, simple installation and reduced maintenance cost. Applications relate to security of public spaces and buildings, down-hole exploration, medical endoscopes, and to communications in the context of remote RF antennas and passive optical networks (PON). An optically powered network can connect widely differing subscribers with low/high bandwidth requirements, asynchronous/synchronous operation, and low/high priority, e.g., energy-preserving small-bandwidth subscribers with ultra-low duty cycles and low network priority (e.g., temperature sensors) in combination with wide-bandwidth subscribers operating at large duty cycles and high priority (e.g., video conferencing). Optical energy is supplied centrally from an access point, and this results in a combined star and tree-like network topology. As a consequence, subscribers communicate with the CO only, and therefore a standard carrier sense multiple access (CSMA) protocol cannot handle the data exchange. We present optically powered subscriber hardware and demonstrate a low-energy medium-access control (LE-MAC) protocol that extends the IEEE 802 standard, allows random and scheduled medium access of subscribers, and, by quality-of-service support, efficiently uses the available resources, namely channel bandwidth and optically supplied energy.