ISDN at NASA Lewis Research Center

An expository investigation of the potential impact of the Integrated Services Digital Network (ISDN) at NASA Lewis Research Center is described. To properly frame the subject, the paper contains a detailed survey of the components of Narrowband ISDN. The principles and objectives are presented as decreed by the Consultative Committee for International Telephone and Telegraph (CCITT). The various channel types are delineated and their associated service combinations are described. The subscriber-access network functions are explained pictorially via the ISDN reference configuration. A section on switching techniques is presented to enable the reader to understand the emergence of the concept of fast packet switching. This new technology is designed to operate over the high bandwidth, low error rate transmission media that characterizes the LeRC environment. A brief introduction to the next generation of networks is covered with sections on Broadband ISDM (B-ISDN), Asynchronous Transfer Mode (ATM), and Synchronous Optical Networks (SONET). Applications at LeRC are presented, first in terms of targets of opportunity, then in light of compatibility constraints. In-place pilot projects and testing are described that demonstrate actual usage at LeRC

Space division multiplexing chip-to-chip quantum key distribution

Quantum cryptography is set to become a key technology for future secure communications. However, to get maximum benefit in communication networks, transmission links will need to be shared among several quantum keys for several independent users. Such links will enable switching in quantum network nodes of the quantum keys to their respective destinations. In this paper we present an experimental demonstration of a photonic integrated silicon chip quantum key distribution protocols based on space division multiplexing (SDM), through multicore fiber technology. Parallel and independent quantum keys are obtained, which are useful in crypto-systems and future quantum network

Rate-Distortion-Based Physical Layer Secrecy with Applications to Multimode Fiber

Optical networks are vulnerable to physical layer attacks; wiretappers can improperly receive messages intended for legitimate recipients. Our work considers an aspect of this security problem within the domain of multimode fiber (MMF) transmission. MMF transmission can be modeled via a broadcast channel in which both the legitimate receiver's and wiretapper's channels are multiple-input-multiple-output complex Gaussian channels. Source-channel coding analyses based on the use of distortion as the metric for secrecy are developed. Alice has a source sequence to be encoded and transmitted over this broadcast channel so that the legitimate user Bob can reliably decode while forcing the distortion of wiretapper, or eavesdropper, Eve's estimate as high as possible. Tradeoffs between transmission rate and distortion under two extreme scenarios are examined: the best case where Eve has only her channel output and the worst case where she also knows the past realization of the source. It is shown that under the best case, an operationally separate source-channel coding scheme guarantees maximum distortion at the same rate as needed for reliable transmission. Theoretical bounds are given, and particularized for MMF. Numerical results showing the rate distortion tradeoff are presented and compared with corresponding results for the perfect secrecy case.Comment: 30 pages, 5 figures, accepted to IEEE Transactions on Communication

Analog free-space optical links.

Free-space optics (FSO) communications is a technology that uses modulated infrared optical beams to transmit information line-of-sight through the atmosphere. There has been a substantial increase in the use of FSO technology over the last few years, mainly for "last mile" applications, because FSO links provide the transmission capacity to overcome bandwidth bottlenecks between backbone optical fiber links and metropolitan concentrations of end users. Optical fiber has been traditionally deployed for the transmission of both digital and analog signals. While transmission techniques for analog radio frequency (RF) intensity-modulated signals over optical fibers is well-established, prior to the investigations presented in this dissertation, there is no report of research on the efficiency of FSO for transmission of analog signals in the technical literature. This dissertation research investigated the effectiveness of FSO to transport modulated RF analog signals and compares key performance measures against those of fiber optic links. In addition, a new method to setup temporary IS-95 CDMA microcells or permanent IS-95 CDMA macrocells using FSO was proposed and its viability investigated. Finally, a new transmission technique for transmitting multiple RF signals (channels) over a single FSO link using wavelength division multiplexing (WDM) technology for potential CATV applications was demonstrated

Performance Studies of a Double-Layered All-Optical Network Architecture

Transmission in complete lightform is now realised with advancements in technology. These include new developments in fabricating the fiber carrier medium, low loss fiber coupling devices, optical switching components for routing lightwave trans mission; laser light sources and sensitive photonic detectors. The in creasing speeds of new generation electronic microprocessors, is capable of resolving the differences in processing and transmission speeds. Access to the medium is regulate d by the medium access control protocol, that permits multiple users to share limited transmission resources of the network. The double-layere dhierarchical all-optical network architecture is proposed, that consists of an upper layer to inter connect sub-networks of the lower layer. The data packets are differentiate d for the two layers . The architecture implements wavelength -space trans mission of wavelength division multiplexed channels. The architecture affords spatial reuse of channels in the lower layer. A non-contentious token-passing medium access protocol is utilised. The token-passing variant that uses one token to provide access to multiple channels is introduced. The performance of the arrayed transmitter of the access node is gauged to determine the suitability of the architecture with the access protocol in supporting multiple accesses. The transmitter can queue a number of data packets awaiting transmission depending on the size of the buffer. Performance indication can be obtained from probabilistic modelling of the changing event states of the transmitter. Performance causal parameters which include the number of nodes, channel allocation and buffer size are defined. The results from the probabilistic models are then analysed and verified with simulation. The architecture provides an inherent feature termed as the bypass that is capitalised to improve performance of the lower layer. Performance indication shows that the architecture is capable of supporting the two types of data packets effectively, and the access protocol is suitable for its purpose. Performance indication of average packet delay improves when the when the bypass feature is implemented. The probabilistic models are found to provide a logical and systematic approach to study and gauge performance of the token-passing access protocol. In conclusion, the double-layered hierarchical AON architecture and the medium access protocol, together serve as a reference for the study of similar scaleable network architectures and their performance

Beyond 5G Fronthaul based on FSO Using Spread Spectrum Codes and Graphene Modulators.

High data rate coverage, security, and energy efficiency will play a key role in the continued performance scaling of next-generation mobile systems. Dense, small mobile cells based on a novel network architecture are part of the answer. Motivated by the recent mounting interest in free-space optical (FSO) technologies, this paper addresses a novel mobile fronthaul network architecture based on FSO, spread spectrum codes, and graphene modulators for the creation of dense small cells. The network uses an energy-efficient graphene modulator to send data bits to be coded with spread codes for achieving higher security before their transmission to remote units via high-speed FSO transmitters. Analytical results show the new fronthaul mobile network can accommodate up to 32 remote antennas under error-free transmissions with forward error correction. Furthermore, the modulator is optimized to provide maximum efficiency in terms of energy consumption per bit. The optimization procedure is carried out by optimizing both the amount of graphene used on the ring resonator and the modulator’s design. The optimized graphene modulator is used in the new fronthaul network and requires as low as 4.6 fJ/bit while enabling high-speed performance up to 42.6 GHz and remarkably using one-quarter of graphene only