This PDF file contains the front matter associated with SPIE Proceedings Volume 9010, including the Title Page, Copyright information, Table of Contents, Introduction, and Conference Committee listing.

This paper discusses and proposes the architectural framework, which is for data center networks. The data center networks require new technical challenges, and it would be good opportunity to change the functions, which are not need in current and future networks. Based on the observation and consideration on data center networks, this paper proposes; (i) Broadcast-free layer 2 network (i.e., emulation of broadcast at the end-node), (ii) Full-mesh point-to-point pipes, and (iii) IRIDES (Invitation Routing aDvertisement for path Engineering System).

Through the recent progress in information oriented society, the required information volume is expanding rapidly. Under these circumstances, high-speed and high-capacity optical communication systems are deployed in the industry. Especially high speed optical transceiver is the key device to realize high-speed system, and the practical development is accelerated in the industry. In order to develop these leading edge products timely, the global standards is strongly demanded in the industry. Based on these backgrounds, Forum standardization bodies such as OIF PLLWG/ IEEE802.3 are energetically creating the standards in the industry. With regard to 100G/400G standardization activities, OIF leads telecom field and IEEE802.3 leads datacom field, and both activities become important recently. In the previous conference, the activities of these standardization bodies till 2012 were reported[1]. In 2013, 100G digitalcoherent transceiver project especially for metro applications had some progress in OIF PLL-WG, whose target form factor is CFP and CFP2. Also 400G transceiver project in datacom field started in IEEE802.3 as 400G Study Group. In this paper, these high-end standardization topics are mainly reviewed and the future direction is also discussed from the technical point of view. In addition, the energy consumption problem for the near future network, triggered by vast increase of the information bandwidth, is also picked up and some related activities are introduced.

One of the most serious challenges facing the exponential performance growth in the information industry is a bandwidth bottleneck in inter-chip interconnects. Optical interconnects with silicon photonics have been expected to solve the problem because of the intrinsic properties of optical signals and the industrial advantages of silicon for use in the electronics industry. We therefore propose an optical interconnect system by using silicon photonics to solve the problem. We examined integration between photonics and electronics and integration between light sources and silicon substrates, and we propose a photonics-electronics convergence system based on these examinations. We also investigated the configurations and characteristics of optical components for the system, including silicon spot-size converters, silicon optical waveguides, silicon optical splitters, silicon optical modulators, germanium photodetectors, and arrayed laser diodes. We then demonstrated the feasibility of the system by fabricating a high-density silicon optical interposer by using silicon photonics hybridly integrated with arrayed laser diodes and monolithically integrated with the other optical components on a single silicon substrate. The pad pitches of optical modulators and photodetectors were designed to be 100 μm so that LSI bare chips were able to contact to them electrically by flip-chip bonding. Since this system was optically complete and closed and no temperature sensitive component was used, we did not need to align the fibers, control the polarization, or control the temperature throughout the experiments. As a result, we achieved errorfree data links at 20 Gbps and high bandwidth density of 30 Tbps/cm² with the silicon optical interposer.

High Performance Computing and High-end Servers make use of optical interconnects today and future design points for these systems are pushing for higher speeds and lower power simultaneously. This paper will review the use of embedded optical interconnects in HPC and cover the latest research records for speed (56Gb/s) and energy efficiency (1pJ/bit) of short reach (<50m) links.

Optical switching has been introduced in intra-data center networks (DCNs) to increase capacity and to reduce power consumption. Recently we proposed a star MIMO OFDM-based all-optical DCN with burst switching and software-defined networking. Here, we introduce the control procedure for the star DCN in detail for the first time. The timing, signaling, and operation are described for each step to achieve efficient bandwidth resource utilization. Furthermore, the guidelines for the burst assembling period selection that allows burst switching without guard interval are discussed. The star all-optical DCN offers flexible and efficient control for next-generation data center application.

We report details of an experimental demonstration involving a 15 meter pointed indoor optical wireless link in the 1550-nm wavelength range, that is comprised of a uni-directional Cable Television (CATV) signal and a bi-directional link comprised of two 10 Gbps data links. Four port wavelength division mux-demuxes have been used on both ends of the link. The CATV transmission system is connected to port 1 of the mux-demux. CATV signal consists of both analog and digital parts, and its bandwidth is 1 GHz. The laser is directly modulated by the CATV signal, and at the receiver end, the optical signal is demodulated and fed to a TV. Port 2 of the mux-demux is left unused. Ports 3 and 4 are used for the 10 Gbps links. A bit error rate tester has been used to generate the 10 Gbps signals that are converted to optical wavelengths by enhanced Small Form Factor Pluggable (SFP+) modules at both ends of the setup. Collimators are used at both ends to transmit the combined optical signal that is the output of the mux and to receive the optical signal by focusing it onto a single-mode fiber as the input of the demux. We present results on the CATV portion of the setup and the bit-error-rate performance of the two 10 Gbps links. This experiment shows the feasibility of using pointed optical links in datacenters as secondary links to alleviate the loads of highly utilized wired connections and improve the overall throughput performance of datacenters.

A 1.3-μm wavelength optical link, which consists of a lens-integrated laser diode and a CMOS optical receiver, was developed. It achieves 25-Gb/s error-free 100-m multi-mode fiber transmission with sensitivity of −6.3-dBm OMA.

The first Brazilian high speed integrated 100G-DPQPSK transmitter on a 4 × 3 mm silicon photonic chip is presented. The novel photonic component allows optical signal generation of advanced modulation formats in 25GHz bandwidth. Furthermore, in this paper we also present our vision on required integrated photonics targeting 400G optical transmission systems.

We discuss recent progress and challenges in realizing Bragg-grating devices on the submicron silicon-on-insulator platform for next-generation optical communications applications, such as on-chip optical interconnects and signal processing. In particular, we focus on grating-assisted, wavelength-selective couplers, known as contra-directional couplers (contra-DCs). In contrast to conventional two-port Bragg gratings operating in the reection mode, contra-DCs are four-port devices with very weak backreections and, therefore, can be easily integrated with other photonic components on a chip. In order to provide a reliable on-chip wavelength-division multiplexing (WDM) solution for high-speed optical interconnects, we have developed high-performance add-drop filters and, furthermore, wavelength multiplexers/demultiplexers with combined advantages of at-top responses, low insertion loss (< 1 dB), and low crosstalk (< -23 dB). These WDM devices are ultra-compact and highly tolerant to temperature uctuations (up to ±50 °C), showing great potential for large-scale integration and low-power consumption. We further discuss a novel four-port Bragg photonic resonator for high-speed, low-power optical switching. Using a coupler-chirped design with uniform Bragg gratings, we have recently achieved an on-chip, continuously tunable photonic delay line with low insertion loss. These system-orientated devices indicate great potential for large-scale integration of Bragg-grating-defined functions using CMOS-compatible silicon photonics technology.

We demonstrate two silicon photonic technologies for fabrication of monolithic photonic devices in standard silicon. Using these technologies, we demonstrate low-loss silicon waveguides (2.34 dB/cm), double-layer 3D waveguides, and waveguide Bragg reflectors in standard silicon for optical interconnects and sensing applications. These technologies simplify integration of electronics and photonics and are possible alternatives to SOI-based technology for implementation of silicon-photonic devices and systems for optical interconnects and sensing.

Ge-on-Si devices are explored for photonic integration. Through the development of better growth techniques, monolithic integration, laser design and prototypes, it was possible to probe Ge light emitters with emphasis on lasers. Preliminary worked shows thermal photonic behavior capable of enhancing lamination at high temperatures. Increase luminescence is observed up to 120°C from L-band contribution. Higher temperatures show contribution from Δ -band. The increase carrier thermal contribution suggests high temperature applications for Ge light emitters. A Ge electrically pumped laser was probed under 0.2% biaxial strain and doping concentration ~4.5×1019cm-3 n-type. Ge pnn lasers exhibit a gain >1000cm-1 with 8mW power output, presenting a spectrum range of over 200nm, making Ge the ideal candidate for Si photonics. Large temperatures fluctuations and process limit the present device. Theoretically a gain of >4000cm- gain is possible with a threshold of as low as 1kA/cm². Improvements in Ge work

Germanium light-emitting devices on silicon for very-short-reach interconnect were investigated theoretically and experimentally. Our approach to enhance light emission is by applying process-induced strain to the germanium active layer. According to first-principles calculations, larger optical gain in germanium with lower carrier density is obtained at a larger tensile strain. In addition to the thermally induced strain caused by the difference of the thermal expansion ratios, process-induced stress was applied to the germanium active layer by fabricating a SiN stressor on it. As for practical light-emitting devices, a laterally injected light-emitting device was fabricated and tested. In the case of this device, the current is laterally injected into the germanium active layer through a thin silicon layer. In this device structure, mode loss caused by free carrier absorption is expected to be small, since the guided mode overlaps slightly with the heavily doped silicon layer. The electroluminescence (EL) property of the device showed a superlinear increase in integrated EL intensity with increasing injection current, indicating that direct recombination is enhanced by L-valley filling. An increase in intensity and red-shift of the EL peaks of the device with a SiN stressor indicate that additional tensile strain was successfully applied to the germanium active layer.

System performance scaling imposes an increase of package-to-package aggregate bandwidths to interface chips in high performance computing. This scaling is expected to encounter several I/O bottlenecks (pin count, speed, power consumption) when implemented in the electrical domain. Several optical interface technologies are being proposed among which silicon photonics, considered as a promising candidate. In this paper we will review the recent progress made in this technology that may enable multi-channel WDM links for package-to-package interconnects: 1.0V drivers with microring modulators and compact manufacturable microring filters with efficient thermal tuning.

In this paper, the effects of gridless spectrum allocation in Wavelength Division Multiplexed (WDM) optical networks are examined. The advanced modulation formats and multi-rate transmissions of the signals, which are key parameters in the optical system project, are taken into account. The consumed spectrum, as well as the impact of linear and nonlinear impairments on the signal transmission, are compared to WDM network adopting standard grid and gridless ITU. To analyze the influence of these physical effects, some key network design parameters are monitored and evaluated, such as the guard band size, the signal occupied bandwidth, the laser power and the quality of channels. The applied signal modulation formats were On/Off Keying (OOK), Quadrature Phase Shift keying (QPSK), and Dual Polarization State Phase Modulation (DP-QPSK), whereas the transmission rate per wavelength was varied from 10 Gb/s to 100Ghz. The guard band, signal band, and laser power were swept and the resulted Bit Error Rate (BER) was estimated from the eye-diagram. Analytical calculations and simulations are conducted in order to evaluate the impact of the gridless spectrum allocation on both the spectral consumption and the signal quality of transmission (QoT). Results reveal that a gridless transmission system reduces the spectral consumption while offering an acceptable QoT. This work was carried out with both analytical modeling and numerical calculation using the Optisystem as well as Matlab.