In this contribution, it is shown how the number of optical sources in WDM-based optical beamforming networks can be reduced. In optical beamforming networks based on several optical carriers and a dispersive medium a correspondence is established between each optical carrier and each antenna element. However, it is feasible to reduce the number of optical sources of the architecture if the optical carriers are reused by means of the combination of dispersive and non-dispersive time delays.
To sum up, this contribution shows how WDM optical beamforming architectures can be simplified combining dispersive and non-dispersive time delays to allow the use of photonic beamforming techniques in large antenna arrays. The number of optical sources of the beamformer, as well as its total size and cost, can be highly reduced using this technique. Experimental results validating the feasibility of the technique are provided.
Programmable switching nodes supporting Software-Defined Networking (SDN) over optical interconnecting technologies arise as a key enabling technology for future disaggregated Data Center (DC) environments. The SDNenabling roadmap of intra-DC optical solutions is already a reality for rack-to-rack interconnects, with recent research reporting on interesting applications of programmable silicon photonic switching fabrics addressing board-to-board and even on-board applications. In this perspective, simplified information addressing schemes like Bloom filter (BF)-based labels emerge as a highly promising solution for ensuring rapid switch reconfiguration, following quickly the changes enforced in network size, network topology or even in content location. The benefits of BF-based forwarding have been so far successfully demonstrated in the Information-Centric Network (ICN) paradigm, while theoretical studies have also revealed the energy consumption and speed advantages when applied in DCs. In this paper we present for the first time a programmable 4x4 Silicon Photonic switch that supports SDN through the use of BF-labeled router ports. Our scheme significantly simplifies packet forwarding as it negates the need for large forwarding tables, allowing for its remote control through modifications in the assigned BF labels. We demonstrate 1x4 switch operation controlling the Si-Pho switch by a Stratix V FPGA module, which is responsible for processing the packet ID and correlating its destination with the appropriate BF-labeled outgoing port. DAC- and amplifier-less control of the carrier-injection Si-Pho switches is demonstrated, revealing successful switching of 10Gb/s data packets with BF-based forwarding information changes taking place at a time-scale that equals the duration of four consecutive packets.
Silicon-photonic 2×2 electro-optical switching elements and modulators based on the carrier depletion mechanism using both dual-resonator and MZI layout configurations have been developed. The passive photonic structures were developed and optimized using a fast design-fabrication-characterization cycle. The main objective is to deliver smallfootprint, low-loss and low-energy silicon photonic electro-optical switching elements and modulators equipped with standard input-output grating couplers and radio-frequency electrical contact tips to allow their characterization in highspeed probe-station setups. The insertion losses, crosstalk, power consumption and BER performance will be addressed for each electro-optical structure. The fabrication steps, including low loss waveguide patterning, pn junction and low resistive ohmic contact formation have been optimized to produce high performance devices with relaxed fabrication tolerances, employing both optical and electron-beam lithography.
We prove theoretically that it is possible to build embedded reflectionless squeezers/expanders using transformation
optics. We illustrate the potential of this finding by proposing an application in which the squeezer is a key element: an
ultra-short perfect coupler for high-index nanophotonic waveguides.
Exploiting the concept of internal surface plasmon polariton (I-SPP) resonances, which appear at non-single metallic
film stacks, we have designed a metamaterial showing a negative effective refractive index within a large bandwidth.
The designed structure consists of an arrangement of several fishnet layers. By properly adjusting the lattice constant and
the thickness of the dielectric slab of the fishnet, an I-SPP mode can be excited at a certain frequency giving rise to a
negative effective refractive index. Thus, the combination of several fishnet layers, each one of them configured to
excite an I-SPP at a different frequency, enables us to extend the bandwidth at which a negative effective refractive
index is achieved, as long as the selected resonances are close enough. Specifically, from a subwavelength chain of two
fishnet layers, the retrieved effective parameters show a negative index behavior in a frequency span of about 44THz
centered at 210THz, owing to the fact that an I-SPP is excited in each fishnet layer at slightly different frequencies.
Optical nonlinear effects have been widely studied in III-V semiconductor photonics. However, nonlinear performance
in silicon photonics is still inefficient. An alternative silicon-based waveguide configuration, which is known as slot
waveguide, has been recently proposed to improve the nonlinear performance in a very efficient way. In the slot
waveguide, the fundamental mode light is highly confined in a very small region, which is called slot, of a low index
contrast material between two silicon high index contrast layers. This enables the introduction of new silicon photonic
devices in which the characteristics of active optical materials can be efficiently exploited for modulation, switching,
sensing, and other applications. Horizontal and vertical slot waveguides for optimum nonlinear performance have been
recently proposed. However, the horizontal slot waveguide is more feasible for nonlinear applications. To increase
nonlinear performance in the horizontal slot region, silicon nanocrystals (Si-nc) embedded in silica (SiO2) have been
proposed to fill the slot region between the two silicon layers. It is achievable nonlinear performance in the horizontal
slot region for down to 50nm thick slots. However, the lower the slot thickness is, the more difficult the coupling to fiber
results. One of the most developed silicon photonics efficient vertical coupling techniques is the grating coupler. We
demonstrate grating couplers for efficient coupling between horizontal slot waveguides and standard single mode fibers.
Broadband and highly efficient horizontal slot waveguide grating couplers have been obtained by means of simulations.
These grating couplers configuration are suitable for nonlinear performance in silicon photonics. It is achieved 61%
maximum coupling efficiency for λ=1550 nm and TM polarization. Furthermore, a 35 nm 1dB-bandwidth is achievable
for the designed grating couplers.
In this work, several building blocks for high-performance all-optical switching on silicon are addressed. The FP6-PHOLOGIC approach is based on exploiting the nonlinear properties of silicon nanocrystals embedded in slot
waveguides, in which propagating light is highly confined.
In this work, we report theoretical and experimental results on the use of Cadmium Telluride (CdTe) doped with Zinc
(Zn) as core material for the development of all-optical photonic devices. We include the design of optical waveguides
for strong field confinement, technological processes to grow CdTe on 6" or 8" wafers (suitable for high-volume
manufacturing) as well as the fabrication and optical characterization of optical waveguides with a CdTe core.
We present the results of a transmission experiment, over 110 km of field installed fiber, for an all-optical 160 Gb/s
packet switching system. The system uses in-band optical labels which are processed entirely in the optical domain
using a narrow-band all-optical filter. The label decision information is stored by an optical flip-flop, which output
controls a high-speed wavelength converter based on ultra-fast cross-phase modulation in a single semiconductor optical
amplifier. The packet switched node is located in between two different fiber sections, each having a length of 54.3-km.
The field installed fibers are located around the city of Eindhoven in the Netherlands. The results show how the all-optical
switch can effectively route the packets based on the optical information and that such packets may be
transmitted across the fiber with an acceptable penalty level.
The routing decision functionality by all-optically interconnecting semiconductor-based all-optical logic gates and flip-flops is demonstrated in the frame of an all-optical packet switching network. We experimentally show that the output of the all-optical 2-bit correlator is capable of toggling the states of the integrated flip-flop every 2.5 ns via an adaptation stage. High extinction ratios are obtained at the output of the flip-flop, which can be used to feed a high-speed wavelength converter to complete the routing functionality of the AOLS node. The potential integration of these SOA-MZI based devices make the proposed approach a very interesting solution for future packet switched optical networks.
In this paper a spectral crosstalk monitoring technique is proposed and demonstrated. The technique is based on optically perform a real-time continuous Fourier Transform (OFT) comprising the whole set of transmitted wavelengths. This approach does not require to stop the channel operation. Once the spectral information has been brought to time domain, the basic parameters as amplitude (channel power) or central wavelength can be evaluated. This technique is theoretically developed and demonstrated in a three channel DWDM system at 10 GBit/s channel bitrate in a proof-of-concept experiment.
In this paper is proposed a novel high spectral efficiency modulation scheme using time-squared pulses forming an orthogonal wavelength division multiplexing. Experimental results show a significant reduction of the interchannel linear crosstalk-induced penalty compared with Gaussian RZ modulation. Simulation studies are in good agreement with experimental results and show the system performance dependence on several multiplexing impairments inherent to this technique. The proposed modulation technique allows a maximum spectral efficiency of 1 bit/s/Hz without any other spectral efficiency enhancement technique like polarisation division multiplexing.
The parallel analysis of Cy5 fluorophore micro-arrays over polycarbonate and polymethyl metacrilate substrates is reported. Sequential printing of biochemical samples, CCD detection, enhanced analysis by signal processing and assay results recording as digital data on a consolidated substrate is demonstrated. The developed equipment finds its application in low-cost high throughput screening of massive chemical, biochemical or cellular agents.
There is an increasing interest in performing many key networking functions in the optical domain to achieve bit rate transparency. Optical header processing is one such key function that may enable fast reading and forwarding of optical packets in the future all-optical packet-switched core network. Many of these optical header processing functions are enabled through the use of all-optical logic gates. The logic XOR gate is of key importance in decision and comparator circuits. A novel architecture of an N-bit logic XOR gate based on a Mach-Zehnder interferometer with feedback is proposed and its performance evaluated by means of simulations. Basically, this architecture consists of an integrated semiconductor-optical-amplifier-based Mach-Zehnder interferometer (SOA-MZI), an optical pulsed control signal, a differential transmission scheme for the input data sequences, and a feedback network. The simulation results show error-free operation at 40 Gbit/s for 16-bit-length words with extinction ratio values better than 16 dB. Furthermore, simulation results of the data power threshold needed for obtaining error-free operation as a function of the peak power of the control pulses are also presented, showing an optimum operating point at about 8 mW. An important application for the proposed SOA-MZI architecture is label processing directly at the optical domain in high-speed all-optical label swapping networks.
Future multi-terabit/s optical core networks require optical technologies capable of managing ultra-high bit rate OTDM/DWDM (optical time division multiplexing/dense wavelength division multiplexing) channels at 160 Gbit/s or higher bit rates. The key functionalities in ultra-high speed network nodes are all-optical wavelength conversion, 3R-regeneration and demultiplexing of OTDM signals. Advanced optical networking techniques (optical add-drop multiplexing and optical routing) are studied in simulations and their performance evaluated considering 160 Gbit/s OTDM/DWDM channels. Performance comparison results for both OADM (optical add-drop multiplexer) and OXC (optical cross-connect) node networking functionalities are shown considering different technologies: semiconductor-optical-amplifier-based symmetric Mach-Zehnder interferometers (SOA-MZI) for wavelength conversion, signal regeneration and demultiplexing, electroabsorption-modulator-based demultiplexers, and wavelength converters based on four-wave mixing in dispersion-shifted fiber. The simulation results show that the SOA-MZI is a promising technology for all-optical signal processing in network nodes mainly due to its signal regeneration capability. At ultra-high bit rates, however, the relaxation time of SOAs considerably limits the operation. A solution to mitigate this problem is to use a differential scheme at the input of the device. Error-free wavelength conversion, signal regeneration and demultiplexing of 160 Gbit/s OTDM signals employing a SOA-MZI with a differential scheme is demonstrated by means of simulations. Furthermore, the parameters of this architecture are optimized to obtain the best performance for each optical networking functionality in OADM and OXC network nodes.
Transmission of light through linear defects in two-dimensional (2D) photonic crystals has been already successfully demonstrated in two ways: numerical simulations and experimental measurements. Recently, novel waveguides have been proposed in which the propagation of photons is performed via hopping due to overlapping between nearest-neighbors defect cavities. These waveguides are commonly referred to as coupled-cavity waveguides (CCW). In this work, we present a comprehensive analysis of the light transmission (TM modes) in CCW's created in hexagonal 2D photonic crystals made of high-index dielectric rods. Numerical simulations of the transmission are performed using a 2D Finite-Difference Time-Domain method. A plane wave algorithm and a simple one-dimensional (1D) tight-binding model are employed to describe the miniband which allows the light transport. It is shown that modifying the individual cavities along the CCW one can control the average frequency and the dispersion relation of the miniband. The results also show that this novel guiding method can be used to develop 1310nm/1550nm Coarse-WDM optical demultiplexers employing bended waveguides.
When rows of cylinders are periodically removed from a hexagonal array of dielectric cylinders, a new two-dimensional (2D) photonic crystal (PC) arises. The new structure consists of a lattice of vacancies embedded in the initial hexagonal lattice. We called it Suzuki Phase because it remains similar structures discovered in the 60's by K. Suzuki studying alkali halides. A plane-wave algorithm as well as a 2D finite difference-time-domain method has been employed to study the photonic properties of this PC as a function of the filling fraction (f) in the case of high dielectric cylinders ((epsilon) equals 13.6) in air. For TM- modes, it is shown that in a certain range of f an isolated miniband appears in the gap of the initial hexagonal lattice. The miniband, which is created by the coupling of defect states, is described by a tight-binding formalism with two parameters. Also, the frequencies of the two possible vacancy defects in the SP have been obtained and their symmetry analyzed.
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