An optical backplane based on Wavelength Division Multiplexing (WDM) for onboard data and signal handling is introduced. It is a tunable transmitter fixed receiver architecture incorporating an NxN Arrayed Waveguide Grating (AWG) element for passive data routing between the nodes. In conjunction with star couplers both unicast and multicast capabilities are offered. The control plane has been implemented on a high-speed FPGA and a four-node demonstrator has been built. Bit-Error-Rate (BER) versus power incident on the receiver, employing three different AWGs, has been measured at a data rate of 10Gbps per link. A total switching time of 500ns has been achieved, leading to more than 95% efficiency with packet lengths greater than 10KBytes.
A wavelength division multiplexing (WDM)-based optical backplane architecture is introduced. It is a tunable transmitter fixed receiver (TT-FR) architecture incorporating an N×N arrayed waveguide grating (AWG) element for passive data routing between the nodes, which in conjunction with star couplers, offers both unicast and multicast capabilities. The data and control plane of the network are implemented on a high-speed field programmable gate array (FPGA), and a four-node demonstrator is built up. Three different types of AWG routing elements implemented in different technologies are employed, and bit error rate (BER) versus incident power on the receiver measurements are presented for a data rate of 10 Gbps per link. A total switching time as low as 500 ns is achieved, permitting packet switching operation with more than 95% efficiency when the packet length is greater than 10 kbytes.
In this paper we report experimental results on InGaAs/InAlAs single quantum wells (SQW) obtained by photoreflectance (PR) between 5 K and 450 K. In the first part of the paper we focus on the evolution of the broadening parameter of E1H1 in the lattice matched 5 nm well width sample, E1H1 and E<SUB>2</SUB>H<SUB>2</SUB> in the lattice matched 25 nm SQW. From this study we derive information about the relative influence of interface roughness, alloy scattering, and electron phonon interactions. In the second part we apply the PR technique to the study of quantum wells near the surface in which we observe an increase of the broadening parameter. These studies show the great interest of PR technique for the qualification of materials and for the surface probe.
The selective area MBE deposition of InGaAs in InP substrates is reported. Successful selective growth of InGaAs in pre-ion etched windows of InP has been achieved utilizing a SILOX mask and lift-off techniques of polycrystalline InGaAs field layers. The optical quality of these epitaxial InGaAs windows was comparable to material deposited on non-patterned InP. An optimized pre-growth heat treatment of InP was very crucial in order to achieve the smooth InGaAs surface morphologies and excellent optical properties. Finally, no significant irregularities were observed at the InGaAs window edges, the alloy composition appeared uniform in the entire window areas and the incorporation of impurities from the SILOX was minimized.
Photoconductivity (PC), photoluminescence (PL), and photoreflectance (PR) have been carried out on In<SUB>0.52</SUB>Al<SUB>0.48</SUB>As/In<SUB>x</SUB>Ga<SUB>1-x</SUB>As single quantum wells, in lattice matched and lattice mismatched composition. The unstrained (x<SUB>In</SUB> equals 0.53) and the strained (x<SUB>In</SUB> equals 0.60) samples have been grown by molecular beam epitaxy (MBE), with well thicknesses of 5 nm and 25 nm. Low temperature PL measurements have shown a narrow full width at half maximum (FWHM) for the unstrained samples, indicating a very good interface quality. In strained samples a broadening on the FWHM has been found, indicating a small degradation of the structure quality with the introduction of strain. With the PC and PR measurements we have been able to observe transitions between electron and heavy holes levels (E<SUB>i</SUB>H<SUB>i</SUB>) up to i equals 5 and also between the first electron and light holes levels (E<SUB>1</SUB>L<SUB>1</SUB>). We have then calculated the theoretical values of these transitions by solving the Schroedinger equation in a finite square well, using an envelope function approximation, an effective mass approximation, and including the effects of strain on the band structure and on the effective mass. For the lattice matched composition, the best fit is obtained for conduction band offset (Delta) Ec equals 0.50 +/- 0.05 eV, in agreement with the literature. For example, with x<SUB>In</SUB> equals 0.60 composition the best fit is obtained for (Delta) Ec equals 0.55 +/- 0.05 eV, in agreement with theory which predicts that (Delta) Ec increases with indium content.