Enhancing data centre networking using energy aware optical interconnects

In a fast changing world where information technology drives economic prosperity, the number of data centres has grown significantly in the past few years. These data centres require large amount of energy in order to meet up with increasing demands. An overview of energy efficient optical interconnects as a means of reducing energy consumption without compromising speed and accuracy was presented. New methods by which energy efficiency can be achieved using OCDMA multiplexing techniques for future optical interconnections were discussed. We also presented some challenges that might inhibit effective implementation of the OCDMA multiplexing scheme

Investigation of all-optical switching OCDMA testbed under the influence of chromatic dispersion and timing jitter

First part of this paper presents an all-optical switching OCDMA testbed investigation under the influence of the residual chromatic dispersion resulted from different locations of the receiving terminal. The investigation was carried out using incoherent 2D-WH/TS OCDMA codes based on picosecond pulses at OC-48 (2.5Gb/s) data rate. The testbed itself is based on a fully chromatic dispersion compensated (with sub-picosecond accuracy) 17 km bidirectional fiber link connecting University of Strathclyde and Glasgow University. We have found that a high performance penalty in the form of BER deterioration was incurred when even a relatively short length of optical fiber was added to a fully compensated transmission link in order to relocate the receiving terminal (we tested increments up to 275m of SMF-28). Second part of this paper reports on the testbed performance when an OCDMA receiver with built in all-optical clock recovery was implemented to mitigate the detrimental effects of the link timing jitter on the picosecond switching based all-optical time gate

In situ method for power re-equalization of wavelength pulses inside of OCDMA codes

A simple in-situ method to equalize power among individual wavelengths pulses representing two-dimensional wavelength-hopping time-spreading OCDMA code originally generated by a fibre Bragg grating-based OCDMA encoder is presented. Experimental data obtained in a field-based multiuser OCDMA testbed shows that applying this method results in system performance enhancements which was demonstrated by observing improved bit error rate (BER) during the field trials

Effect of variations in environmental temperature on 2D-WH/TS OCDMA code performance

Extensive research has been carried out on the performance investigation of two-dimensional wavelength hopping/time spreading optical code division multiple access (OCDMA) codes, which are based on picosecond multiwavelength pulses under the influence of temperature variations resulting from changing environmental conditions. Equations have been derived to theoretically evaluate the extent to which such temperature changes will degrade the overall OCDMA system performance. To mitigate these negative effects on the OCDMA system, several steps have been introduced to improve the code robustness. System design improvements have then been investigated. We also found they would help to improve the spectral efficiency

Investigating the scalability of incoherent OCDMA systems based on ultrashort optical pulses

In a world where bandwidth hungry applications are constantly being churned out to an ever ready sea of consumers most of which are eager to experience the latest means of accessing information of various size and formats, there is an ever growing need for increased network capacity to cope with these demands. Optical code division multiple access (OCDMA) technology has long been researched as a possible solution for high bandwidth multi-access networking. The focus of my investigation is on incoherent OCDMA systems based on two-dimensional wavelength-hopping time-spreading (2D-WH/TS) incoherent OCDMA codes that utilize picosecond multi wavelength pulses. I have conducted experiments to characterise the encoding process of the incoherent optical CDMA transmitter which utilises low cost fibre Bragg gratings (FBG) based all optical encoders and decoders. I have tested the viability and practicality of the incoherent OCDMA system by conducting analysis of its performance under real-life conditions. I have investigated the performance of the picosecond code based optical signal when subjected to temperature variations similar to that experience by most buried fibre systems. I have proposed and demonstrated a novel hybrid system that combined the best of OCDMA and optical time division multiple access (OTDMA) to achieve increased network scalability. The field based demonstration was performed over a fully chromatic dispersion compensated 17-km bidirectional fibre link between Strathclyde and Glasgow University. The compensation of the chromatic dispersion of the link was maintained with sub-picosecond accuracy.In a world where bandwidth hungry applications are constantly being churned out to an ever ready sea of consumers most of which are eager to experience the latest means of accessing information of various size and formats, there is an ever growing need for increased network capacity to cope with these demands. Optical code division multiple access (OCDMA) technology has long been researched as a possible solution for high bandwidth multi-access networking. The focus of my investigation is on incoherent OCDMA systems based on two-dimensional wavelength-hopping time-spreading (2D-WH/TS) incoherent OCDMA codes that utilize picosecond multi wavelength pulses. I have conducted experiments to characterise the encoding process of the incoherent optical CDMA transmitter which utilises low cost fibre Bragg gratings (FBG) based all optical encoders and decoders. I have tested the viability and practicality of the incoherent OCDMA system by conducting analysis of its performance under real-life conditions. I have investigated the performance of the picosecond code based optical signal when subjected to temperature variations similar to that experience by most buried fibre systems. I have proposed and demonstrated a novel hybrid system that combined the best of OCDMA and optical time division multiple access (OTDMA) to achieve increased network scalability. The field based demonstration was performed over a fully chromatic dispersion compensated 17-km bidirectional fibre link between Strathclyde and Glasgow University. The compensation of the chromatic dispersion of the link was maintained with sub-picosecond accuracy

Improving multi access interference suppression in optical CDMA by using all-optical signal processing

This paper presents the study of a novel alloptical method for processing optical CDMA signals towards improving suppression of multi access interference. The main focus is on incoherent OCDMA systems using multiwavelength 2D-WH/TS codes generated using FBG based encoders and decoders. The MAI suppression capabilities based on its ability to eliminate selective wavelength pulse processing have been shown. A novel transmitter architecture that achieves up to 3dB power saving was also presented. As a result of hardware savings, processing cost will be significantly reduced and power budget improvement resulted in improved performance

Novel method for multi access interference suppression in multiwavelength FBG-encoded OCDMA

We present a method for suppressing multi access interference in 2D-WH/TS OCDMA systems. The systems analysed here uses codes that are generated using integrated fiber Bragg grating based encoder/decoders. The method is unique because of its ability to process OCDMA signals without need for demultiplexing and selective processing. This will lead to a significat reduction in the cost of processing multiwavelegth OCDMA signals and enhance system performance. Power budget reduction was also achieved

All-optical clock recovery for OCDMA systems with optical time gating

Implementing time gating in ultra-high speed OCDMA networks over long distance transmissions will require precise synchronization in order to suppress the influence of timing jitter on the OCDMA receiver. To implement optical gating, an optical clock is needed to control a switching window i.e., “a time gate” to pass the desired autocorrelation peak while blocking the MAI noise. We demonstrate that the use of a network global clock distribution is not necessary if the receiver synchronization is done via optical clock recovery. In our experimental demonstration a wider eye opening with power budget improvement of ∼7.5 dB was achieved when using all-optical clock recovery compare to clock distribution

Improving network scalability using OCDMA over OTDM

We analyze and present a field demonstration of an incoherent OCDMA over OTDMA system. The performance analysis shows significant scalability improvement without any significant system performance degradatio

Towards green high capacity optical networks

The demand for fast, secure, energy efficient high capacity networks is growing. It is fuelled by transmission bandwidth needs which will support among other things the rapid penetration of multimedia applications empowering smart consumer electronics and E-businesses. All the above trigger unparallel needs for networking solutions which must offer not only high-speed low-cost "on demand" mobile connectivity but should be ecologically friendly and have low carbon footprint. The first answer to address the bandwidth needs was deployment of fibre optic technologies into transport networks. After this it became quickly obvious that the inferior electronic bandwidth (if compared to optical fiber) will further keep its upper hand on maximum implementable serial data rates. A new solution was found by introducing parallelism into data transport in the form of Wavelength Division Multiplexing (WDM) which has helped dramatically to improve aggregate throughput of optical networks. However with these advancements a new bottleneck has emerged at fibre endpoints where data routers must process the incoming and outgoing traffic. Here, even with the massive and power hungry electronic parallelism routers today (still relying upon bandwidth limiting electronics) do not offer needed processing speeds networks demands. In this paper we will discuss some novel unconventional approaches to address network scalability leading to energy savings via advance optical signal processing. We will also investigate energy savings based on advanced network management through nodes hibernation proposed for Optical IP networks. The hibernation reduces the network overall power consumption by forming virtual network reconfigurations through selective nodes groupings and by links segmentations and partitionings