This paper analyzes bit-error-rate (BER) performance of various optical network-on-chip topologies, taking into account signal losses and crosstalk components along the signal paths. A novel optical interconnect topology, using multiple-segment buses, is proposed which offers an encouraging BER performance within the acceptable limit of per-wavelength launched power (1.5mW).

We propose a redundant radix based number (RBN) representation for encoding and transmitting data for applications which typically utilize low cost devices and demand low power operations with simple modulation techniques like ASK, OOK and FSK. Coupled with silent periods for communicating the digit zero, this encoded communication scheme, called as RBNSiZeComm, provides a highly energy-efficient technique for data transmission. Considering an n-bit data representation and assuming that each of the 2nbinary strings is equally likely to occur, theoretically obtainable fraction of energy savings by using our proposed RBNSiZeComm transmission protocol is, on an average, 1 - n+2/4n. A hybrid modulation scheme using FSK and ASK with non-coherent detection based receiver for the RBNSiZeComm protocol has been presented. Assuming equal likelihood of all possible binary strings of a given length, there is nearly 53% savings in energy on an average at the transmitter relative to binary FSK, over additive white gaussian noise (AWGN) channels. Simulation results demonstrate that compared to binary FSK, our proposed implementation can extend the battery life of devices from about 33% to 62% on an average in applications like remote healthcare and wireless sensor networks for agriculture.

Wireless sensor networks typically require low cost devices and low power operations. Hence, such networks usually employ radios with only simple modulation techniques such as ASK, OOK and FSK. We propose a new energy efficient communication scheme for wireless sensor networks that is based on the ternary number system encoding of data. An efficient algorithm for conversion from binary to ternary and vice versa is used that does not involve any division or multiplication but only addition. Our Ternary with Silent Symbol (TSS) communication scheme is similar in concepts to the RBNSiZeComm protocol proposed. However, in contrast to RBNSiZeComm, TSS simultaneously saves energy at both the transmitter and receiver due to shortening of the transmission duration. We also propose a transceiver design that uses a hybrid modulation scheme utilizing FSK and ASK so to keep the cost/complexity of the radio devices low. With a non-coherent detection based receiver and assuming equal likelihood of all possible binary strings of a given length, there is a savings of about 20% in energy on an average at the transmitter compared to binary FSK, for additive white gaussian noise (AWGN) channels. Simultaneously, there is a savings of 36.9% at the receiver too, due to the reduced length of ternary encoded transmitted data, compared to binary encoding. Coupled with the low cost and low complexity of the transceiver, these results establish the effectiveness of TSS as a suitable candidate for communication in low power wireless sensor networks.

Optical burst switching (OBS) is a promising technique for supporting high-capacity, bursty data traffic over optical wavelength-division-multiplexed (WDM) networks. An optical link failure may result in a huge amount of data (and revenue) loss, and it has been an important survivability concern in optical networks. In this paper, we study the fault- management issues related with a link failure in an OBS network. We propose to use pre-planned global rerouting to balance network load and to reroute bursts after a link fails. We apply optimization techniques to pre-plan explicit backup routes for failure scenarios. Our objective is to achieve optimal load balancing both before and after a failure such that the network state can still remain stable with minimum burst-loss probability when a failure occurs. We apply the pre-planned normal and backup routing tables to an OBS network, and study the network performance after a failure occur using illustrative numerical examples. The results show that the average burst-loss probability can be significantly reduced by 60% - from an average of 0.10 to 0.04 (when the normalized link load is less than 0.5) using globally-rerouted backup routes, when compared with the scheme without global rerouting. We also observe that the burst-loss probability is reduced by 43% - from an average of 0.07 to 0.04 (when the link load is less than 0.5) if the rerouting is done using optimization techniques, when compared with shortest-path routing.for Fault Management

Optical burst switching (OBS) is a promising technique for supporting high-capacity bursty data traffic over optical wavelength-division-multiplexed (WDM) networks. A label-switched path can be established to forward a burst control packet (BCP) if each OBS node is augmented with an IP/MPLS controller. Such a network is called a labeled OBS (LOBS) network, and it can exploit the explicit routing and constraint-based routing properties supported in the MPLS framework to perform traffic and resource engineering. However, the burst-loss probability (denoted as BLP) can be large if the traffic is not properly engineered in a LOBS network, especially after a failure occurs. In this paper, we propose to use pre-planned global rerouting to balance network load and to restore bursts after a link fails. We apply optimization techniques to pre-plan explicit backup routes for failure scenarios. Our objective is to achieve optimal load balancing both before and after a failure such that the network state can still remain stable with minimum BLP when failure occurs. We apply the pre-planned global rerouting method in a LOBS network and study the performance of different rerouting schemes on some typical network topologies. Our illustrative numerical examples show that the BLP can be significantly reduced by 25%-99% (when the average link load is less than 0.5) using globally rerouted backup routes, when compared with the scheme without global rerouting. We also observe that the BLP is reduced by 20%-65% (when the average link load is less than 0.5) if the rerouting is done using optimization techniques, when compared with shortest-path routing.

The problem of formulating a suitable access protocol for hierarchically designed optical wavelength division multiplexed (WDM) metropolitan area networks (MANs) is studied. The proposed network uses a two level hierarchy. Groups of nodes, located nearer to each other, are inter-connected through passive optical broadcast stars, which represent level-0 clusters. These level-0 clusters are connected to each other through an active wavelength routing switch (WRS). We consider a slotted-ALOHA based access protocol for both intracluster and intercluster communications and evaluate the performance of the proposed protocol in terms of network throughput and delay. Our study reveals that, even for such a simple protocol, WRS enhances the throughput of the system considerably with respect to the passive star-on-star configuration.

Node architectures which are being considered for wavelength-routed WDM optical networks do not provide a high degree of scalability with respect to the number of wavelengths in the system. In this investigation, we propose a new node architecture which allows new wavelengths to be added to the network without significant additional costs. We study the performance of such nodes in a network environment, and we develop a simple cost model for the network. We show that the proposed architecture provides a higher degree of scalability as well as significant cost benefits when compared to a traditional node architecture, such as the wavelength-routing switch (WRS) or a wavelength-selective cross-connect (WSXC), while also maintaining comparable performance in terms of blocking probability.

This paper examines the problem of self bit synchronization employing nonlinear timing extraction schemes in optical receivers with avalanche photodetectors (APD) through digital computer simulation. A direct algorithm is developed for the simulation of sample functions of the APD output process with due consideration to intersymbol interference (ISI). Simulation of all the functional blocks used for synchronization is carried out in the discrete time domain. Performances of the nonlinear timing recovery schemes are evaluated in terms of the rms timing jitter for nonreturn-to-zero (NRZ) as well as return-to-zero (RZ) signaling formats.