The efficiency of generating four-wave mixing (FWM) from phase-modulated (PM) optical signal is studied. An analysis, that takes bit shifts occurring during fiber propagation due to group velocity differences into account, indicates that the FWM efficiency from PM signals is smaller than that from continuous waves in fiber transmission lines whose distance is longer than the walk-off length between transmitted optical signals.

A Brillouin optical correlation domain reflectometry (BOCDR) system, which can set measuring point to arbitrary distance that is aligned in a random order along an optical fiber (i.e., random accessibility), is proposed to measure dynamic strain and experimentally evaluated. This random-access system can allocate measurement bandwidth to measuring point by assigning the measurement times at each measuring point of the total number of strain measurements. This assigned number is not always equally but as necessary for plural objects with different natural frequencies. To verify the system, strain of two vibrating objects with different natural frequencies was measured by one optical fiber which is attached to those objects. The system allocated appropriate measurement bandwidth to each object and simultaneously measured dynamic strain corresponding to the vibrating objects.

The needs for ultra-high speed short- to medium-reach optical fiber links beyond 100-Gbit/s is becoming larger and larger especially for intra and inter-data center applications. In recent intensity-modulated/direct-detection (IM/DD) high-speed optical transceivers with the channel bit rate of 50 and/or 100 Gbit/s, multilevel pulse amplitude modulation (PAM) is finally adopted to lower the signaling speed. To further increase the transmission capacity for the next-generation optical transceivers, various signaling techniques have been studied, especially thanks to advanced digital signal processing (DSP). In this paper, we review various signaling technologies proposed so far for short-to-medium reach applications.

A number of all-optical signal processing schemes based on nonlinear optical effects have been proposed and demonstrated for use in future photonic networks. Since various modulation formats have been developed for optical communication systems, all-optical converters between different modulation formats will be a key technology to connect networks transparently and efficiently. This paper reviews our recent works on all-optical modulation format conversion technologies in order to highlight the fundamental principles and applications in variety of all-optical signal processing schemes.

5G infrastructures will heavily rely on novel paradigms such as Network Function Virtualization and Service Function Chaining to build complex business chains involving multiple parties. Although virtualization of security middleboxes looks a common practice today, we argue that this approach is inefficient and does not fit the peculiar characteristics of virtualized environments. In this paper, we outline a new paradigm towards autonomous security assurance in 5G infrastructures, leveraging service orchestration for semi-autonomous management and reaction, yet decoupling security management from service graph design. Our work is expected to improve the design and deployment of complex business chains, as well as the application of artificial intelligence and machine learning techniques over large and intertwined security datasets. We describe the overall concept and architecture, and discuss in details the three architectural layers. We also report preliminary work on implementation of the system, by introducing relevant technologies.

For any positive integer n, define an iterated function $f(n)=left{ egin{array}{ll} n/2, & mbox{ $n$ even, } 3n+1, & mbox{ $n$ odd. } end{array} ight.$ Suppose k (if it exists) is the lowest number such that fk(n)

Price-based power control problem is investigated in the spectrum sharing cognitive radio networks (CRNs) by Stackelberg game. Using backward induction, the revenue function of the primary user (PU) is expressed as a non-convex function of the transmit power of the secondary users (SUs). To solve the non-convex problem of the PU, a branch and bound based price-based power control algorithm is proposed. The proposed algorithm can be used to provide performance benchmarks for any other low complexity sub-optimal price-based power control algorithms based on Stackelberg game in CRNs.

This paper studies the performance of the quantitative RF power variation in Radio-over-Fiber beam forming system utilizing a phased array-antenna integrating photo-diodes in downlink network for next generation millimeter wave band radio access. Firstly, we described details of fabrication of an integrated photonic array-antenna (IPA), where a 60GHz patch antenna 4×2 array and high-speed photo-diodes were integrated into a substrate. We evaluated RF transmission efficiency as an IPA system for Radio-over-Fiber (RoF)-based mobile front hall architecture with remote antenna beam forming capability. We clarified the characteristics of discrete and integrated devices such as an intensity modulator (IM), an optical fiber and the IPA and calculated RF power radiated from the IPA taking account of the measured data of the devices. Based on the experimental results on RF tone signal transmission by utilizing the IPA, attainable transmission distance of wireless communication by improvement and optimization of the used devices was discussed. We deduced that the antenna could output sufficient power when we consider that the cell size of the future mobile communication systems would be around 100 meters or smaller.

This letter proposes a comprehensive assessment of the mission-level damage caused by cyberattacks on an entire defense mission system. We experimentally prove that our method produces swift and accurate assessment results and that it can be applied to actual defense applications. This study contributes to the enhancement of cyber damage assessment with a faster and more accurate method.

This paper proposes fabrication process of a pyramidal electromagnetic (EM) absorber made by natural rubber. The advantage of this research is to generate value-added latex from Thai rubber and to reduce number of chemical absorber by using natural rubber based absorber. The proposed absorber in the research is mainly made from latex with carbon black filler. The proposed absorber is in the form of rubber foam which provides suitable characteristics to serve as an EM absorber. The results of this research are chemical formulas for fabrication of pyramidal rubber foam with carbon black filler. The fabrication cost is very low when compared to an available commercial absorber. The electrical properties of the proposed EM absorber are measured. Also the reflectivity is measured and compared well with a commercial EM absorber.

Multi-static Primary Surveillance Radar (MSPSR) has recently attracted attention as a new surveillance technology for civil aviation. Using multiple receivers, Primary Surveillance Radar (PSR) detection performance can be improved by synthesizing the reflection characteristics which change due to the aircraft's position. In this paper, we report experimental results from our proposed optical-fiber-connected passive PSR system with transmit signal installed at the Sendai Airport in Japan. The signal-to noise ratio of experimental data is evaluated to verify moving target detection. In addition, we confirm the operation of the proposed system using a two-receiver setup, to resemble a conventional multi-static radar. Finally, after applying time correction, the delay of the reflected signal from a stationary target remains within the expected range.

We propose a novel bit error rate (BER) analysis model of weighted-type fractional Fourier transform (WFRFT)-based systems with WFRFT order offset Δα. By using the traditional BPSK BER analysis method, we deduce the equivalent signal noise ratio (SNR), model the interference in the channel as a Gaussian noise with non-zero mean, and provide a theoretical BER expression of the proposed system. Simulation results show that its theoretical BER performance well matches the empirical performance, which demonstrates that the theoretical BER analysis proposed in this paper is reliable.

Improvement of output and lifetime is a problem for biofuel cells. A structure was adopted in which gelation mixed with agarose and fuel (fructose) was sandwiched by electrodes made of graphene-coated carbon fiber. The electrode surface not contacting the gel was exposed to air. In addition, grooves were added to the gel surface to further increase the oxygen supply. The power density of the fuel cell was examined in terms of the electrode area exposed to air. The output increased almost in proportion to the area of the electrode exposed to air. Optimization of the concentration of fuel, gel, and the amount of enzyme at the cathode were also examined. The maximum power density in the proposed system was approximately 121μW/cm2, an enhancement of approximately 2.5 times that in the case of using liquid fuel. For the power density after 24h, the fuel gel was superior to the fuel liquid.

In cloud computing environments, data processing systems with strong and stochastic stream data processing capabilities are highly desired by multi-service oriented computing-intensive applications. The independeny of different business data streams makes these services very suitable for parallel processing with the aid of multicore processors. Furthermore, for the random crossing of data streams between different services, data synchronization is required. Aiming at the stochastic cross service stream, we propose a hardware synchronization mechanism based on index tables. By using a specifically designed hardware synchronization circuit, we can record the business index number (BIN) of the input and output data flow of the processing unit. By doing so, we can not only obtain the flow control of the job package accessing the processing units, but also guarantee that the work of the processing units is single and continuous. This approach overcomes the high complexity and low reliability of the programming in the software synchronization. As demonstrated by numerical experiment results, the proposed scheme can ensure the validity of the cross service stream, and its processing speed is better than that of the lock-based synchronization scheme. This scheme is applied to a cryptographic server and accelerates the processing speed of the cryptographic service.

The potential transmission capacity of a standard single-mode fiber peaks at around 100Tb/s owing to fiber nonlinearity and the bandwidth limitation of amplifiers. As the last frontier of multiplexing, space-division multiplexing (SDM) has been studied intensively in recent years. Although there is still time to deploy such a novel fiber communication infrastructure; basic research on SDM has been carried out. Therefore, a comprehensive review is worthwhile at this time toward further practical investigations.

Pseudorandom number generators are required to generate pseudorandom numbers which have good statistical properties as well as unpredictability in cryptography. An m-sequence is a linear feedback shift register sequence with maximal period over a finite field. M-sequences have good statistical properties, however we must nonlinearize m-sequences for cryptographic purposes. A geometric sequence is a sequence given by applying a nonlinear feedforward function to an m-sequence. Nogami, Tada and Uehara proposed a geometric sequence whose nonlinear feedforward function is given by the Legendre symbol, and showed the period, periodic autocorrelation and linear complexity of the sequence. Furthermore, Nogami et al. proposed a generalization of the sequence, and showed the period and periodic autocorrelation. In this paper, we first investigate linear complexity of the geometric sequences. In the case that the Chan-Games formula which describes linear complexity of geometric sequences does not hold, we show the new formula by considering the sequence of complement numbers, Hasse derivative and cyclotomic classes. Under some conditions, we can ensure that the geometric sequences have a large linear complexity from the results on linear complexity of Sidel'nikov sequences. The geometric sequences have a long period and large linear complexity under some conditions, however they do not have the balance property. In order to construct sequences that have the balance property, we propose interleaved sequences of the geometric sequence and its complement. Furthermore, we show the periodic autocorrelation and linear complexity of the proposed sequences. The proposed sequences have the balance property, and have a large linear complexity if the geometric sequences have a large one.

Low-density chaotic binary sequences generated by Bernoulli map are discussed in this paper. We theoretically evaluate auto-correlation functions of the low-density chaotic binary sequences based on chaos theory.

We normally hold a lot of confidential information in hard disk drives and solid-state drives. When we want to erase such information to prevent the leakage, we have to overwrite the sequence of information with a sequence of symbols independent of the information. The overwriting is needed only at places where overwritten symbols are different from original symbols. Then, the cost of overwrites such as the number of overwritten symbols to erase information is important. In this paper, we clarify the minimum cost such as the minimum number of overwrites to erase information under weak and strong independence criteria. The former (resp. the latter) criterion represents that the mutual information between the original sequence and the overwritten sequence normalized (resp. not normalized) by the length of the sequences is less than a given desired value.

Reverberation chambers (RCs) are used widely in the electromagnetic measurement area. An RC is designed to have a long reverberation time, generate numerous modes, and provide good field uniformity within the chamber. The purpose of this paper is to describe the design process and measurement of the KRISS Reverberation Chamber (KRC). KRC models with 4.5m × 3.4m × 2.8m dimensions are simulated by 3D numerical simulation software. The field uniformity and correlation coefficient are then analyzed at 200MHz to obtain the optimized model. The simulation results show good performance in terms of field uniformity and are confirmed by measurement from 200MHz to 1GHz. The lowest usable frequency (LUF) of KRC was confirmed by field uniformity to be 200MHz. However, the stirrer correlation coefficient results show good performance above 300MHz.

Cyber attacks targeting specific victims use multiple intrusion routes and various attack methods. In order to combat such diversified cyber attacks, Threat Intelligence is attracting attention. Attack activities, vulnerability information and other threat information are gathered, analyzed and organized in threat intelligence and it enables organizations to understand their risks. Integrated analysis of the threat information is needed to compose the threat intelligence. Threat information can be found in incident reports published by security vendors. However, it is difficult to analyze and compare their reports because they are described in various formats defined by each vendor. Therefore, in this paper, we apply a modeling framework for analyzing and deriving the relevance of the reports from the views of similarity and relation between the models. This paper presents the procedures of modeling incident information described in the reports. Moreover, as case studies, we apply the modeling method to some actual incident reports and compare their models.