Daniel C. Kilper

Optical performance monitoring

Progress in optical networking has stimulated interest in optical performance monitoring (OPM), particularly regarding signal quality measures such as optical signal-to-noise ratio (SNR), Q-factor, and dispersion. These advanced monitoring methods have the potential to extend fault management and quality-of-service (QoS) monitoring into the optical domain. This paper reviews OPM applications and techniques, while examining the role of OPM as an enabling technology for advances in high-speed and optically switched networks.

Power Trends in Communication Networks

Power trends in communication networks are analyzed using a transaction-based model. Traffic models are developed for North America and used to evaluate the relative power trends of wireline networks and mobile networks through 2020. An ideal case for aggressive network-efficiency improvement measures is evaluated within this framework and shown to lead to roughly unchanged consumption over the next decade. Implications for future technology requirements are discussed.

Energy-Optimal Mobile Cloud Computing under Stochastic Wireless Channel

This paper provides a theoretical framework of energy-optimal mobile cloud computing under stochastic wireless channel. Our objective is to conserve energy for the mobile device, by optimally executing mobile applications in the mobile device (i.e., mobile execution) or offloading to the cloud (i.e., cloud execution). One can, in the former case sequentially reconfigure the CPU frequency; or in the latter case dynamically vary the data transmission rate to the cloud, in response to the stochastic channel condition. We formulate both scheduling problems as constrained optimization problems, and obtain closed-form solutions for optimal scheduling policies. Furthermore, for the energy-optimal execution strategy of applications with small output data (e.g., CloudAV), we derive a threshold policy, which states that the data consumption rate, defined as the ratio between the data size (L) and the delay constraint (T), is compared to a threshold which depends on both the energy consumption model and the wireless channel model. Finally, numerical results suggest that a significant amount of energy can be saved for the mobile device by optimally offloading mobile applications to the cloud in some cases. Our theoretical framework and numerical investigations will shed lights on system implementation of mobile cloud computing under stochastic wireless channel.

In-network caching effect on optimal energy consumption in content-centric networking

In content-centric networking (CCN), the in-network caching feature provides several attractive advantages such as low dissemination latency and network transport load reduction. Thus, CCN requires less transport energy but additional energy to provide a caching capability at every content router. In this paper, we investigate the minimum energy consumption that CCN can achieve with optimal cache locations by considering different caching hardware technologies, number of downloads per hour, and content popularity. We first set up an energy consumption model for CCN and then formulate linear and nonlinear programming problems to minimize total energy consumption of CCN. Also, a genetic algorithm (GA) approach is proposed to find energy-efficient cache locations. Using reported energy efficiency of computational hardware and network equipment, we show CCN yield greater energy savings for very popular content and small-sized catalog, compared to conventional CDN. Our results also indicate that two aspects of the memory technology, energy-proportional caching and sufficient memory capacity, are critical to the overall energy efficiency gain of CCN.

Linear optical sampling

We demonstrate the measurement of waveforms and eye diagrams at high bit rates by optical sampling using coherent detection. By simultaneously recording two orthogonal quadratures of the interference between the data stream and a sampling pulse with two balanced detectors, we are able to cancel the phase sensitivity inherent to linear optics. As the device is based on linear optics and square-law low-speed photodetectors, its sensitivity is 1000 times better than nonlinear optical sampling techniques, which makes it attractive for optical signal characterization and monitoring. This new diagnostic tool was used to measure eye diagrams at 10, 40, and 80 Gb/s, and is projected to operate at 160 Gb/s and higher.

Toward energy-efficient content dissemination

A major role of todays Internet is to provide efficient content dissemination among users, such as distributing multimedia content and sharing user generated data. To meet the ever increasing demands, the Internet has been rapidly growing, and it now includes a web of tens of millions of networked devices ranging from content servers to core and edge routers to home gateways. Due to the sheer numbers, however, it is reported that these devices, such as those used for content delivery, consume a considerable amount of energy. While optimizing the energy efficiency of data centers is well studied in the literature, understanding the energy efficiency of various content dissemination strategies has received comparatively little attention thus far. In this article we review existing content dissemination architectures and survey the energy efficiency of various network devices used for content delivery. The energy efficiency comparison using simple trace-based simulations reveals that a change from a host-oriented to a content-centric networking model can substantially improve energy efficiency of content dissemination. Our preliminary results are encouraging and will stimulate further research in this direction.

8 – ROADMs and their system applications

Publisher Summary Subsystem and system vendors are rapidly developing and producing reconfigurable optical add/drop multiplexers (ROADMs), and carriers are installing and deploying them in their networks. This chapter is a comprehensive treatment of ROADMs and their application in WDM transmission systems and networks, comprising a review of various ROADM technologies and architectures, analyses of their routing functionalities and economic advantages, and considerations of design features and other requirements. The complex interplay between ROADM properties and optical transmission has also been explored, including a detailed discussion of static and dynamic channel power control. ROADMs enable an automated and transparent network capable of rapid reconfiguration. To fully realize this vision within the growing global communication fabric, transmission systems must be capable of dealing with continual changes, including power transients and varying transmission conditions. Network management systems must solve complex problems in routing and wavelength blocking, path verification, and more as the photonic layer assumes some of the tasks previously handled by higher layers. Advanced ROADM functionality, such as colorless add/drop ports, steerable transponders, and adaptive passbands, will be increasingly sought after, as will new and better solutions for signaling, network management, and mesh transmission. By meeting these challenges, the optical R&D community will help address the worlds need for flexible, economical, and scalable networks.

Optical performance monitoring using data stream intensity autocorrelation

We demonstrate optical performance monitoring (OPM) using intensity autocorrelations of 10-Gb/s return-to-zero (RZ) data. Data stream intensity autocorrelations are used for the quantitative determination of the optical signal-to-noise ratio (OSNR) and accumulated dispersion values up to half the Talbot dispersion. Autocorrelations are performed using sensitive two-photon absorption in photon counting silicon avalanche photodiodes. Simulations and experimental results demonstrate the retrieval of optical signal-to-noise ratio values in the presence of large accumulated dispersion

Monitoring optical network performance degradation due to amplifier noise

The relationship between optical performance as monitored within a network and the end terminal optical signal-to-noise ratio (OSNR) and bit error ratio (BER) is measured for the case of performance degradation due to amplified spontaneous emission noise. Measurements on 10-Gb/s signals reveal that performance monitoring sensitivity to OSNR levels of 26 dB is sufficient for identifying degradations that impact the end terminal BER.

Energy Challenges in Current and Future Optical Transmission Networks

In this paper, we examine how energy constraints might shape future optical communication networks and the impact that current technology trends may have on future energy use. Historical factors and prevailing complications associated with fiber capacity point to an increased focus on energy to enable tighter photonic and electronic component integration and larger networks. Energy requirements and associated challenges are described at the component, system, and network level.