Frequency shift measurement of Brillouin Phaseshift Spectrum (BPS) by Brillouin optical time-domain analysis (BOTDA)-based optical fiber sensors is an attractive approach to realizing fast and high-resolution distributed strain, vibration, and temperature monitoring. This paper proposes a system that employs a multistage coherent detection technique based on an intradyne optical phase-diversity receiver at the front stage and electrical coherent receiver at the second stage. In the sensing optical fiber, probe light within the Brillouin scattering bandwidth co-propagates with a pilot light that has the same optical phase as the probe light at the input of the sensing optical fiber. Those lights are converted into complex electrical signals with the help of a local light at the optical polarization-phase diversity receiver. The second stage electrical coherent receiver, implemented on a digital processing platform cancels optical phase fluctuation between probe/pilot light and local light, and detects the Brillouin Phase-shift Spectrum by comparing the phase of the complex electrical signals extracted from the probe and pilot light. Proof-of-concept experiments of BPS measuring BOTDA conducted on a 1 km long sensing section of a 10 km transmission fiber are performed and highly sensitive detection with the total power of probe and pilot light power as low as -32-dBm, which is 10dB lower than that attained in the previous study, is demonstrated; the standard deviation of measured Brillouin Frequency Shift is 2.1 MHz.

This letter proposes a visible light indoor position tracker employing a newly developed Angle of Arrival (AOA) with Multiple Input Multiple Output (MIMO) channel model algorithm. The position tracker utilizes indoor illumination lights and a photodiode(PD) array. An adaptive digital spatial filter attached to the output of the PD array performs MIMO signal processing and decomposes the light signals received from different illumination light sources that are simultaneously input to the PD array. The position tracker then estimates the angle of arrival of each light signal and finally its position from that data. This letter demonstrates a position tracker with an adaptive digital filter tuning the Least Mean Square (LMS) algorithm and evaluates its positioning error performance. Experiments show excellent performance as the positioning errors were as low as 0.05 m in an indoor environment with dimensions of 1.75×2×2 m.

This paper investigates the impact of nonlinear optical effects on Time-Domain Single Carrier Index Modulation (TDSC-IM) optical signals in Wavelength Division Multiplexing-Passive Optical Network (WDM-PON) systems that use standard single-mode fibers. Simulations indicate that TDSC-IM optical signals with high peak-to-average power ratio (PAPR) can maintain sufficient signal-to-noise ratios (SNRs) in C-band transmission in optical delivery networks with standard single mode fibers, while O-band transmission suffers larger nonlinear effects. This paper demonstrates that the degradation in the SNRs of the 25 GBaud quaternary phase shift keying (QPSK) based TDSC-IM optical signals can be less than 1 dB for 8 wavelength channel WDM-PON systems with 50 GHz spacing.

Index modulation has received a lot of interest in the wireless communication field in the last decade, since this technology can enhance the data transmission rate per energy (Eb/N0) in low signal power conditions. This gain originates from the utilization of index activation patterns that can transmit part of the data without consuming additional energy. This inherent characteristic of index modulation can be used to develop a new elastic optical fiber access service that supports energy efficient intermediate data rates in ultra-low signal power conditions. We evaluate the receiver sensitivity of a Time-Domain Single Carrier (8,1,BPSK) Index Modulation optical signal with symbol rate of 2.5 GBaud for the first time. We confirm 3 dB gain in Eb/N0 values and 6 dB margin to maintain optical link connectivity compared to BPSK optical signaling.

This paper studies non-integer power of two-ary quadrature amplitude modulation (QAM) for long-haul optical fiber transmission systems. Numerical simulations show that 12-QAM and 24-QAM provide intermediate solutions on reachable transmission distances among traditional M-QAM such as C8-QAM, 16-QAM, and 32-QAM. In addition, short block length probabilistic shaping of 24-QAM not only provides an intermediate solution with nonlinear tolerance, but also yields greater transmission distances than 16-QAM for the same information data rates.

This paper addresses the issue of implementing a sequence for restoring fiber links and communication paths that have failed due to a catastrophe. We present a mathematical formulation to minimize the total number of steps needed to restore communication paths. We also propose two heuristic algorithms: Minimum spanning tree - based degree order restoration and Congestion link order restoration. Numerical evaluations show that integer linear programming based order restoration yields the fewest number of restoration steps, and that the proposed heuristic algorithms, when used properly with regard to the accommodation rate, are highly effective for real-world networks.

Elastic optical networks (EONs) represent a promising network architecture that accommodates a wide variety of traffic demands in the optical layer. Thanks to the functionality of bandwidth flexibility of elastic optical paths, we can now accommodate IP traffic directly into the optical layer by configuring, for example, the modulation format and subcarrier counts to client demands (optical path demands). At the same time, to accommodate temporally and geographically changing IP traffic demands efficiently in optical networks, cooperation between the IP and optical layers is essential. This paper proposes a multilayer network reconfiguration algorithm that supports periodically changing IP traffic patterns. We incorporate two schemes, which make IP over EONs more flexible, into the heuristic iterative multilayer network reconfiguration algorithm (IMNR). The first scheme involves bandwidth resizing achieved through subcarrier expansion and reduction, and the second employs energy-efficient adaptive modulation according to the data rate and distance of the client demands. We evaluated the impact of the following on energy efficiency: the IMNR algorithm, the proposed adaptive bandwidth resizing and modulation schemes, and some multicarrier-based transponder architectures including bandwidth-variable transponder (BVT) and sliceable BVT (SBVT). The evaluation results show that the IMNR algorithm with the proposed schemes significantly reduces the energy consumption compared with traditional network planning schemes and equipment.

Network function virtualization is regarded as a promising candidate for future networks. Although many advantages are expected, there is still a lack of services that directly link to increased revenue for telecom operators. Therefore, we propose a new NFV-based service, virtual network integration as a service (VNIaaS). The service allows enterprise network administrators to construct and monitor virtual enterprise networks as necessary. As a key enabler, we further propose vConductor, an innovative technology due to its automatic network provisioning, multi-objective resource scheduling, and NFV-oriented inventory management characteristics. Finally, we show the feasibility through implementation of a prototype system. We believe that this contribution will be a catalyst to accelerate the industrialization of NFV.

With the continuing growth in the amount of backbone traffic, improving the cost-effectiveness and ensuring survivability of the underlying optical networks are very important problems facing network service providers today. In this paper, we propose a bandwidth squeezed restoration (BSR) scheme in our recently proposed spectrum-sliced elastic optical path network (SLICE). The proposed BSR takes advantage of elastic bandwidth variation in the optical paths of SLICE. It enables spectrally efficient and highly survivable network recovery for best-effort traffic as well as bandwidth guaranteed traffic, while satisfying the service level specifications required from the client layer networks. We discuss the necessary interworking architectures between the optical path layer and client layer in the BSR in SLICE. We also present a control framework that achieves flexible bandwidth assignment as well as BSR of optical paths in SLICE. Finally, we describe an implementation example of a control plane using generalized multi-protocol label switching (GMPLS).

This article describes the first multi-area multiprotocol label switching and generalized MPLS interoperability trial over a reconfigurable optical add/drop multiplexer and optical cross-connect network. The interoperability trial demonstrated the routing of label switched paths over a multi-area GMPLS controlled ROADM/OXC network and the control of Ethernet over MPLS transport service on top of the GMPLS network. The trial was conducted using various network elements provided by 14 institutions and was carried out in Tokyo and Virginia. This article introduces the motivation for the trial, technical issues related to controlling multiarea MPLS/GMPLS networks, test network topology, and experimental results. The results show that the interior gateway routing protocolbased multi-area routing architecture is a promising solution for the nationwide deployment of GMPLS networks within a carrier domain. In addition, this article discusses the technical issues of routing constraints in ROADM/OXC networks and the limit of multiarea routing without the Path Computation Element Protocol. © 2009 IEEE.

Bolstering survivable backbone networks against multiple failures is becoming a common concern among telecom companies that need to continue services even when disasters occur. This paper presents a multiple-failure recovery scheme that considers the operation and management of optical paths. The presented scheme employs scheme escalation from pre-planned restoration to full rerouting. First, the survivability of this scheme against multiple failures is evaluated considering operational constraints such as route selection, resource allocation, and the recovery order of failed paths. The evaluation results show that scheme escalation provides a high level of survivability even under operational constraints, and this paper quantitatively clarifies the impact of these various operational constraints. In addition, the fundamental functions of the scheme escalation are implemented in the Generalized Multi-Protocol Label Switching control plane and verified in an optical-cross-connect-based network.

Traffic engineering in backbone networks is an important issue in supporting an appropriate QoS level to accommodate various types of traffic flows efficiently. Automatically switched optical networks and generalized multiprotocol label switching control planes are promising functionalities to achieve the sophisticated mechanism of interdomain traffic engineering. In this article we address dynamic operational scenarios to control IP traffic flows using the ASON/GMPLS control plane. This includes cut-through IP/MPLS routers and the rerouting of failed links through the tunnel of optical label-switched paths. This article presents an operational evaluation of traffic engineering. More specifically, we present QoS recovery for protecting high priority traffic using policy controllers and fault recovery of inter-domain LSPs over the JGN II network testbed. This article evaluates and discusses the feasibility of these operational scenarios using state-of-the-art optical switching and control- plane technologies.

To utilize network resources effectively and guarantee the system reliability in Internet exchanges (IXs) in the future, the use of photonic IXs that employ optical cross connects and generalized multiprotocol label switching is considered. This paper presents a theoretical and experimental study of link-capacity adjustment for a photonic IX employing a statistical-decision method for traffic monitoring. We present parameter estimation of the statistical-decision method in detail considering the traffic characteristics in IXs. Then, experiments on the link-capacity adjustment are presented. The first experiment shows the link-capacity adjustment of an optical path to evaluate path addition from one path to two and path deletion from two optical paths to one. The second experiment shows the link-capacity adjustment using multiple paths. We confirmed that there is no packet/frame loss in either experiment during the transmission of demo traffic, which simulates daily traffic changes.

The objective of this paper is to survey the Generalized Multi-Protocol Label Switching (GMPLS) based recovery technology for optical transport networks. This paper introduces standardization activities of the GMPLS based recovery technology in the Internet Engineering Task Force (IETF), and recent progress of related experiments. In addition, this paper extracts requirements for the GMPLS based recovery technology through the evaluation of existing network elements, which can be client nodes of the optical transport networks. The results of field evaluations on the GMPLS based recovery technology are also introduced in this paper. Then, this paper addresses the issues for future deployment of the GMPLS based recovery technology for the optical transport networks.

In this paper the current trends in the optical networking including the physical components, technologies and control architectures are discussed. The possible interaction schemes and implementation models of the automatic communication between applications and network as well as between ASON/GMPLS based network domains are proposed. Finally, the related research activities based on simulation results of control plane dimensioning are illustrated and real test bed experiments on OIF worldwide interoperability demonstration and the ongoing European IST project MUPBED are disseminated.

Generalized Multi-protocol Label Switching (GMPLS) technologies are expected a key technology that creates high-performance Internet backbone networks. There were many GMPLS interoperability trials. However, most of them reported the successful results only. How to set up a trial network and how to test it was generally not discussed. In this paper, as a kind of tutorial, detailed GMPLS field trials in the National Institute of Information and Communications Technology (NICT) Kei-han-na Info-Communication Open Laboratory, Interoperability Working Group (WG) are reported. The interoperability WG is aiming at the leading edge GMPLS protocol based Inter-Carrier Interface that utilizes wide-bandwidth, cost-effective photonic technology to implement IP-centric managed networks. The interoperability WG is a consortium for researching the GMPLS protocol and advancing a de facto standard in this area. Its experimental results, new ideas, and protocols are submitted to standardization bodies such as the International Telecommunications Union-Telecommunication standardization sector (ITU-T), the Internet Engineering Task Force (IETF), and the Optical Internetworking Forum (OIF). This paper introduces the activities of the interoperability WG; they include a nationwide GMPLS field trial using the JGN II network with multi-vendor, multi-switching-capable equipment and a GMPLS multi routing area trial that used a multi-vendor lambda-switching-capable network.

近年のIP系ブロードバンドサービスの拡大によるトラヒックの増大に伴い,波長多重技術,光スイッチング技術,自律制御プロトコル技術を用いた光ネットワークが注目されている.しかし,複数の装置及び複数のレイヤで構成されたネットワークを統合的に管理し,効率的なネットワーク運用をサポートするマルチレイヤネットワーク管理技術についての検討は十分とはいえない.本論文ではGMPLS制御機構を有する光クロスコネクト装置及びコアルータ装置で構成されたMPLS/SDH/OTNマルチレイヤネットワークを対象として,統合管理に向けた課題を明確化するとともに,マルチレイヤパスの管理モデル,パス制御管理方式,故障管理方式,及びSRLGの概念に基づくリスク,コスト優先制御管理方式について提案する.更に,試作による機能確認,GMPLSによる開通方式とネットワーク管理システムによる開通方式との比較評価についても述べる.

At iGrid2005, we conducted a live demonstration where our Grid scheduling system co-allocated computing and network resources with advance reservation through Web services interfaces using the Grid Resource Scheduler (GRS), the Network Resource Management System (NRM), which is capable of GMPLS network resource management, and a GMPLS-based network test-bed, for the first time. The goal of the G-lambda project is to define a standard Web services interface (GNS-WSI) between GRS and NRM that is acceptable for both application service providers and commercial network operators, and which can be used as a tool for realizing new and emerging commercial services. (c) 2006 Elsevier B.V. All rights reserved.

The concept of an optical path layer has become increasingly attractive with the growth of traffic in the backbone network. The recent advances in optical switching technology support the deployment of optical cross-connect (OXC) nodes and the construction of large-scale optical path networks. This paper proposes a highly-reliable and fast pre-assigned restoration scheme for optical path networks. To achieve the pre-assigned restoration scheme, this paper investigates the extension of the Generalized Multi-Protocol Label Switching (GMPLS) protocol functionality considering the interoperability with GMPLS capable IP routers in the future. This paper also proposes a new network control architecture called the "partition model" through discussion of network architecture. We clarify that the M:N end-to-end restoration scheme achieves efficient resource usage and management of the network especially in the "partitioned model" network. With the finite design of the GMPLS protocol extension based on the M:N end-to-end restoration scheme, we successfully achieve an intelligent protocol that guarantees 100% recovery against single link failure and is capable of protection grade fast restoration of the optical path less than 50 msec. To our knowledge, this is the first demonstration of GMPLS-controlled protection grade fast optical path restoration.

In this paper, the authors propose novel nongrooming, optical path cross-connect (OXC), single-layer optical path (OP) networks that can route multigranularity optical paths with reduced optical switch (OSW) size. Since the multigranularity OP's are handled in one OP layer, the configuration and path administration of the OXCs become simple. The authors evaluate the network topology dependency of the network elements, i.e., the required number of OSW ports and fibers in networks consisting of 36 fixed nodes with different network topologies as well as that of a 16-OXC, 25-link NSFNET. The proposed networks require 60% fewer OSW ports, enabling efficient link resource utilization. A 60% reduction in total network cost is also confirmed.

This article presents two dynamic multilayer routing policies implemented in the photonic MPLS router developed by NTT for IP+optical generalized MPLS networks. According to IP traffic requests, wavelength paths called lambda label switched paths are set up and released in a distributed manner based on GMPLS routing and signaling protocols. Both dynamic routing policies first try to allocate a newly requested electrical path to an existing optical path that directly connects the source and destination nodes. If such a path is not available, the two policies employ different procedures. Policy 1 tries to find available existing optical paths with two or more hops that connect the source and destination nodes. Policy 2 tries to establish a new one-hop optical path between source and destination nodes. The performances of the two routing policies are evaluated. Simulation results suggest that policy 2 outperforms policy 1 if p is large, where p is the number of packet-switching-capable ports; the reverse is true only if p is small. We observe that p is the key factor in choosing the most appropriate routing policy. We also describe items that need to be standardized in the IETF to effectively achieve multilayer traffic engineering.

This paper presents two dynamic multi-layer routing policies for optical IP Networks. Both policies first try to allocate a newly requested electrical path to an existing optical path that directly connects the source and destination nodes. If such a path is not available, the two policies employ different procedures. Policy 1, which has been published already, tries to find available existing optical paths with two or more hops that connect the source and destination nodes. Policy 2, which is proposed in this paper, tries to establish a new one-hop optical path between source and destination nodes. The performances of the two routing policies are evaluated. Simulation results suggest that policy 2 outperforms policy I if p is large, where p is the number of packet-switching-capable ports; the reverse is true only if p is small. We observe that p is the key factor in choosing the most appropriate routing policy.

This paper proposes a distributed virtual network topology (VNT) reconfiguration method for Internet protocol over wavelength-division-multiplexing network under dynamic traffic demand. We developed a simple heuristic algorithm for calculating the VNT for distributed control. Generalized multiprotocol, label switching (GMPLS)-based routing protocol has been developed. The VNT is quickly reconfigured by setting up and/or tearing down lightpaths using GMPLS signaling protocol. Traffic demand is measured at the ingress node and advertised by the extended GMPLS routing protocol. Performance of the proposed method is investigated using variable traffic model.

The noise figure (NF) of a phase-sensitive parametric amplifier using a nonlinear Mach-Zehnder interferometer (NMZI) with Kerr media is analyzed for amplitude-modulation signals. In the analysis, the distributed loss of the Kerr media and the excess noise of the pump light are taken into account. As for the distributed loss of the Kerr media, the quantum Langevin equation for the NMZI is derived and solved. The results elucidate a simple degradation factor in the NF representation of the amplifier. This factor implies that the NF can be less than the standard quantum limit (SQL) of 3 dB, even if the total loss of the Kerr media exceeds 3 dB. As for the excess noise of the pump light, the semi-classical small signal analysis is utilized. The results clearly indicate that the signal-to-noise ratio of the pump light must be four times higher than that of the input signal in order to realize a low-noise optical amplifier under the SQL of 3 dB.

A new extended signaling and traffic engineering method for the GMPLS-based photonic and electrical multilayer router (Hikari router) is proposed. The method allows dynamic optical network management and photonic signal recovery, such as regeneration, reshaping, etc., to be realized adaptively. Wavelength conversion is also adaptive, which reduces network cost. Multilayer traffic engineering, which yields the dynamic cooperation of IP and photonic layers, is described to provide IP services cost effectively. To realize multilayer traffic engineering, we propose the OSPF extension, which advertises both the number of total wavelengths and the number of unused wavelengths, and the RSVPTE extension, which minimizes the number of wavelength conversions needed. In addition, this paper proposes a heuristics-based multilayer topology design scheme that uses IP traffic measurements in a generalized multi-protocol label switch (GMPLS). The proposed scheme yields the optical label switch path (OLSP) network topology, that is, OLSP placement, that minimizes network cost, in response to fluctuations in IP traffic demand. In other words, the OLSP network topology is dynamically reconfigured to match IP traffic demand. Networks are reconfigured by the proposed scheme so as to utilize network resources in the most cost effective manner.

Coherent optical amplifiers intensify the amplitude of the component which has a given optical phase and attenuate the amplitude of the component which has the optical phase orthogonal to the 'amplified phase'. Principles, effectiveness in the optical transmission and current status of experimental demonstrations of the coherent amplifiers are reviewed.

コヒーレント光増幅器は,コヒーレント光検波技術と光パラメトリック増幅技術を併用することで,光位相に依存したパワー利得を実現する線形光増幅器である.この特徴的な動作により,既存のレーザー光増幅器,ラマン光増幅器などの限界とされる標準量子限界(雑音指数3dB)以下の低雑音光増幅が原理的に可能とされる.また,光周波数チャーピングにより波形がひずんだ超短パルスの波形整形動作も実現可能である.本稿では,このコヒーレント光増幅器の原理と,最近の研究動向について紹介する.

The first demonstration of an inline coherent optical amplifier with a noise figure which is lower than the 3dB quantum limit is presented. The amplifier is based on optical phase-sensitive amplification using a nonlinear fibre Sagnac interferometer pumped by an injection-locked semiconductor laser with a compensation phase-locked loop. A noise figure of 2.0dB with a high signal gain of 16dB has been successfully obtained.

This paper investigates the gain characteristics of coherent optical amplifiers that amplify only one of two quadrature phase components in an input signal light according to the phase of pump light. It is constructed around a Mach-Zehnder interferometer with Kerr media. To heuristically obtain the design parameters of the coherent optical amplifier, small-signal analysis is adapted to the Mach-Zehnder interferometer with Kerr media. The theoretical results are then compared to experimental results and shown to agree well, which confirms the validity of this design approach. By utilizing low-loss and high-nonlinearity silica fiber as the Kerr medium and optimizing its length, a coherent optical amplifier is constructed that yields high-gain (up to 26 dB) operation.

A noise figure which is less than the standard quantum limit of 3dB has been observed for the first time in a high gain phase-sensitive fibre parametric amplifier. A noise figure of 1.8dB with a 16dB signal gain was measured by a precisely calibrated electrical spectrum analyser.

This paper describes an in-line optical phase-sensitive amplifier (PSA) with a pump laser whose optical phase is locked to that of a randomly modulated signal by using an optical phase-lock loop (OPLL). The OPLL is designed with the capability of optical phase locking at an arbitrary relative phase. Experimental evaluation is presented of the OPLL employing a newly developed external cavity semiconductor ring laser with a spectrum linewidth df less than 20 kHz. Employing this pump laser with the OPLL in conjunction with a 4.4-km long nonlinear fiber Sagnac interferometer (NFSI) yields optical phase-sensitive gain of up to 11 dB, A randomly modulated signal is successfully amplified and confirmed offering a clear eye-opening.

Optical phase-sensitive amplifiers (PSAs) are promising circuit elements for expanding the regenerative repeater spacing of optical transmission systems. The authors first demonstrate error-free operation of in-line PSAs with a 10dB net gain by using an injection-locked pump with a compensation phase-locked loop.

This paper shows the theoretically derived performance of single channel, amplitude modulation/direct detection optical transmission systems using in-line optical phase-sensitive amplifiers (PSA's), The calculations take into account the degradation of the signal-to-noise power ratio (SNR) and intersymbol interference (ISI) due to the distortion of transmitted signal pulses. The SNR is analyzed by considering not only amplifier noise and fiber loss but also noise enhancement by four-wave mixing in the transmission fiber. The ISI is estimated by eye-pattern degradation of the transmitted signal numerically calculated using the nonlinear Schrodinger equation. The regenerative repeater spacing of in-line PSA systems limited by SNR and ISI can be expanded by approximately 3 to 10 times that of in-line EDFA systems, in the case of \D\ less than or equal to 0.1 ps/nm/km dispersion fiber systems transmitting a 40-Gb/s signal.

An in-line optical phase-sensitive amplifier with a phase-locked pump source is demonstrated. The pump source, which consists of a modelocked semiconductor ring laser, is phase-locked to the input signal light by optical injection of the signal. The randomly modulated signal pulses are successfully amplified in a Sagnac interferometer-type parametric amplifier pumped by the injection-locked laser.

Randomly modulated signal pulses from an independent source are successfully amplified by a phase-sensitive amplifier with an internal pump light whose optical phase is locked to that of the injected signal using an optical phase-locked loop.

The linewidth of the individual modes of an actively mode-locked extended-ring-cavity semiconductor laser is reduced from a free running linewidth of over 200-20 kHz by the injection of a narrow linewidth continuous-wave (CW) tight. The optical phase of the injection-locked pulses can be controlled by adjusting the free-running optical frequency of the semiconductor ring laser. The variation in the optical phase of the output pulses versus the change of the free-running optical frequency is evaluated to be 0.57 pi radians within the locking range of about 96 MHz by observing temporal shape of the beat signal formed between output pulses and CW injection light.

Optical phase-sensitive amplification using individual pump and signal light sources is presented for the first time. In the experiment, optical phase of pump and signal light is locked by an optical phase-locked loop (OPLL). Stable optical phase-locking is achieved and optical phase-sensitive amplification with a gain of 12dB is successfully demonstrated using a nonlinear Sagnac interferometer.

In optical fiber transmission systems near the zero-dispersion wavelength that use in-line erbium-doped fiber amplifiers (EDFA's), the enhancement of optical amplifier noise caused by four-wave mixing (FWM) in transmission fibers degrades signal-to-noise ratio (SNR) excessively. We theoretically show that the enhancement of amplifier noise by the FWM in transmission fibers can be effectively eliminated by implementing in-line phase-sensitive amplifiers (PSA's). Small-signal analysis of the nonlinear Schrodinger equation shows that the transmission distance limited by the SNR of an in-line PSA system is expanded four times more than that of an in-line EDFA system. (C) 1997 Optical Society of America

A phase sensitive gain of 23dB is achieved using a pulse excited nonlinear loop mirror with a 3km zero dispersion optical fibre. It is shown that the phase sensitive amplifier (PSA) behaves as a limiting amplifier in the high input signal power region. The suppression of amplitude fluctuation in the input signal is also demonstrated using the PSA as a limiting amplifier.

Theoretical design of ZnSSe/ZnCdSSe laser diodes emitting 460 nm at room temperature (RT) was studied by means of threshold current analysis. The threshold current density calculation was based on the laser theory established for the III-V laser diode (LD) system. The result of the threshold current density calculation indicated that the reduction of carrier overflow is an essential issue in realizing the device with a reasonable threshold current level at RT. Another indication is that 30% S content in the ZnSSe cladding layer would be a suitable target value for a practical 460 nm LD at RT, along with a multiple quantum barrier structure. The predicted threshold current density of such a LD could be as low as 450 A/cm(2) at RT.

In transparent optical networks, the optical path accommodation design must consider the continuous wavelength allocation constraint from source to destination and the transmission impairment constraint. The optical path accommodation schemes considering those two constraints are classified into the pre-planning scheme and the post-planning scheme. In this paper, we propose the re-allocation scheme in the pre-planning scheme in order to minimize the expansion of the facility cost even in the case of demand fluctuation and clarify the effectiveness of the proposed scheme through quantitative evaluation.

We propose the multi-layer path configuration management system that constructs and manages the accommodation relation of path between layers of multi-layer network in cooperation with GMPLS automatically. We describe about the path management model of GMPLS to construct the accommodation relation of multi-layer path. Moreover, associating the passing management data constructed with GMPLS and the passing management data of a high-ranking operation system is clarified. Specific speed-up of the grasp related to the accommodation of multi-layer path and the extent of the impact of the breakdown occurrence can be expected by using this system.

AIST, KDDI R&D Laboratories and NTT are promoting collaborative project G-lambda to establish a standard Web services interface between Grid and network resources. At iGrid2005, we conducted a experiment in cooperation with NICT, where our Grid scheduling system coallocated computing and network resources with advance reservation through the interface. In this report, our co-allocation system model, the Web services interface (GNS-WSI) between GRS (Grid Resource Scheduler) and NRM (Network Resource Management System), overview of GRS which AIST has developed and NRM which KDDI R&D laboratories developed, and overview of the experiment are described.

Photonic networks (PNW's) need to be robust against failures as very high-speed optical paths (OP's) like 2.5Gbps, 10Gbps, and so forth, are operated therein. In particular, failure recovery scheme against multiple failures is essential to establish highly reliable PNW. This paper intends to open up an opportunity for the reliability enhancement of PNW, particularly, against multiple failures, and proposes a novel multiple-failure recovery scheme where both pre-assigned and dynamic restorations gracefully co-functions. We begin with network dimensioning using the OP accommodation design tool we developed to determine the effectiveness of the proposed recovery scheme in terms of the survivability. We then implemented a couple of policies as to how pre-assigned and dynamic restorations are co-related into the OP accommodation design tool to find out the criterion determining the order of setting up new OP.

Label-switching nodes with Generalized Multi-Protocol Label Switching (GMPLS) controller have been convened much attention as a promising way to realize next-generation IP back-bone network, which emphasizes the importance of the reusability of the GMPLS controller, bunch of huge volume softwares, to reduce development, deployment and maintenance costs of the nodes. This paper focuses on a generic specification of a switch management and control interface as a mean of reducing these costs. This paper studies General Switch Management Protocol (GSMP) standardized in Internet Engineering Task Force (IETF) for further generalization and adaptation to photonic network. Then, this paper reports the result of performance evaluation of phonic MPLS routers with the GSMP studied.

Photonic IP networks that integrate wavelength routing and layer 3 cut-through capability are promising candidate to transport large capacity IP traffic effectively. This paper proposes multi-layered optimal accommodation design algorithms that accommodates both LSPs (Label Switched Paths) and OLSPs (Optical LSPs) considering IP traffic for multi-layered photonic IP networks with LSP and OLSP layer. In order to enhance the reliability of networks, we employ optical path restoration scheme considering route independency of working and back-up paths, and evaluate the number of fibers which is needed whole Photonic IP networks. Simultaneously, we clarified advantages and disadvantages considering route independency.

This paper presents two dynamic multi-layer routing policies for optical IP Networks. Both policies first try to allocate a newly requested electrical path to an existing optical path that directly connects the source and destination nodes. If such a path is not available, the two policies employ different procedures. Policy 1, which has been published already, tries to find available existing optical paths with two or more hops that connect the source and destination nodes. Policy 2, which is proposed in this paper, tries to establish a new one-hop optical path between source and destination nodes. The performances of the two routing policies are evaluated. Simulation results suggest that policy 2 outperforms policy 1 if p is large, where p is the number of packet-switching-capable ports p; the reverse is true only if p is small. We observe that p is the key factor in choosing the most appropriate routing policy.

This paper proposes a scaleable SRG-based restoration method in shared mesh wavelength-routed networks. We introduce a backup-SRG concept to identify which SRG is backed up by individual links. We developed an admission control method for backup path using the backup-SRG concept to achieve 100% recovery performance. The proposed method is extended to support networks with a large number of SRGs by introducing hierarchical SRG assignment technique.

This paper discusses the requirements for extending routing protocols to realize IP+Photonic multi-layered networking under the Generalized Multi-Protocol Label Switching (GMPLS) controller. This paper also proposes dynamic optical-path generation algorithms and evaluates their impact on the performance of the IP+Photonic multi-layered GMPLS network comprising label-switching routers with integrated packet and lambda switching capability. Then, the optical label-switched path (O-LSP) Creation First (OCF) strategy is elucidated, which provides excellent throughput in high network capacity.

So far, we have evaluated that a grouped-wavelength-path, which is a bundle of wavelength continuous paths between a node pair, could suppress the node scale, securing node throughput with a simple node configuration. This method, however, requires more bandwidth than conventional wavelength routing because of the vacant path in the grouped-wavelength-path. To accomplish the node scale suppression, efficient resource utilization, and simple configuration, we propose wavelength / grouped-wavelength setting node which handle these paths in each format, and compare it with conventional wavelength path routing node in terms of the amount of NW elements required for traffic load. Furthermore, we evaluated cross talk in lump wavelength converter. Wavelength converter is the key device for the grouped-wavelength routing to attain the node scale suppression. Crosstalk of Optical fiber (FWM) and Periodically Poled LiNbO_3(PPLN:χ_2Cascading) is evaluated theoretically as an example of one lump wavelength converter.

We propose OSPF extension and light path routing algorithms in photonic networks to resolve the RWA (Routing and Wavelength Assignment) problem. We extend OSPF to advertize the wavelength status and wavelength conversion status for each link. A light routing path is calcurated using them. In this paper, we describe the evaluation results of our light path routing algorithms.

This paper proposes a simple dynamic traffic engineering method in hierarchical GMPLS networks. Virtual topologies in optical and electrical layers are re-configured in a graceful way responding the traffic demand change. The electrical layer re-routing is done first with make-before-break technique assuming the anticipated virtual optical layer topology before the optical layer rerouting is done. The proposed method satisfies the six goals, which we raised: (1) simple, (2) fast, (3) efficient, (4) adaptive, (5) minimum disruptive, and (6) stable. The protocol extensions are addressed to support the proposed method. By exchanging the traffic demand matrix between border nodes, each border node determines the order nodded, to which it should set up the light-path.

This paper presents the performance of distributed-controlled dynamic wavelength-conversion (DDWC) optical networks based on our simple route and wavelength assignment (RWA) policy. A source node first chooses an optical-path route by using aggregated optical link-state information, then sends a signaling message on the selected route, after which wavelength assignment is performed. If wavelength conversion is needed at a transit node, the wavelength is adaptively converted by using trunk-type wavelength converters. The advertised information overhead incurred by the routing protocol and the cost processing incurred in solving the complicated RWA problem at the source node are reduced. We show via simulations that the performance of the DDWC network with our simple RWA policy emulates that of the WC network with small number of trunk-type wavelength converters.

This paper discusses the requirements for extending routing protocols to realize IP+Photonic multi-layered networking under the Generalized Multi-Protocol Label Switching (GMPLS) controller. This paper also proposes dynamic optical-path generation algorithms and evaluates their impact on the performance of the IP+Photonic multi-layered GMPLS network comprising label-switching routers with integrated packet and lambda switching capability. Then, the optical label-switched path (O-LSP) Creation First (OCF) strategy is elucidated, which provides excellent throughput in high network capacity.

Multi-layer traffic engineering which yields the dynamic cooperation of IP and photonic layers, is required to provide IP services cost-effectively. This paper proposes a heuristic-based multi-layer topology design scheme that uses IP traffic measurements in generalized multi-protocol label switch (GMPLS). The proposed scheme yields the optimu optical label switch path (OLSP) network topology i.e. OLSP placement, to minimze network cost in response to fluctuations in IP traffic demand. In other words. OLSP network topology is dynamically reconfigured to match IP traffic demand. Networks reconfignred by the proposed scheme utilize the network resources cost-effectively.

To support large amount of data traffic, optical path routing nodes are required to route a large number of paths efficiently without increasing the number of NW elements such as optical switch ports and transmission fibers. In this paper, we introduce Higher Order Optical Path(HO-OP)that bundles several optical paths for the purpose of reducing network elements, and evaluate its merits by using path accommodation setting simulations. This method can decrease not only the number of switch ports but also NW total elements.

Coherent optical amplifiers can principally breakthrough the standard quantum limit of the 3-dB noise figure imposed on conventional amplifiers such as laser and Raman amplifiers. This paper analyzes the noise characteristics of the coherent optical amplifier using Kerr medium theoretically and experimentally. In theoretical analysis, we derived the quantum Langevin equation of a lossy Kerr medium, and obtained the quantum field operator and the photon number variation of output signal. In experimental study, we utilized a nonlinear fiber Sagnac interferometer as optical gain medium and achieved stable optical amplification by locking optical phase between signal and pump using optical injection with compensation PLL. The electrical spectrum analyzer method was employed for the noise figure measurement. By using a high nonlinearity fiber with the length of 3 km, the loss coefficient of -0.7 dB/km, and the nonlinear coefficient of 15.8/W/km, we successfully obtained low-noise figure optical amplification under the standard quantum limit, 2.0-dB noise figure with 16-dB gain.

位相感応型光増幅器(PSA)は、光非線形媒質中の縮退パラメトリック(縮退四光波混合)過程により、光位相に依存した光信号利得を実現する。そのためPSAは、伝送ファイバの分散及び非線形効果に起因したチャープでパルス幅の広がった信号光パルスを波形整形できることが理論的に指摘されている。しかしながら、励起光-信号光間の光位相同期が困難であり、実験的な検証はこれまでされていなかった。本稿では励起光-信号光間の光位相同期を光PLLで実現し、PSAの光位相依存利得特性を用いた信号光波形整形動作を実験的に確認したので報告する。

光周波数偏移幅がマイクロ波発信器の精度で、かつ信号光の光位相を保持したままでの光波長変換技術は将来の光位相を利用する光リンク/ネットワークの構築上重要である。今回、信号光の有する光位相を維持したコヒーレントな波長変換を目指して、入射する信号光にオフセット光位相同期したレーザ光で励起されたファイバ四光波混合実験を行った。その結果、入射光の線幅が保存された波長変換に成功したので報告する。

This paper clarifies the relationship between optical gain and fiber parameters of optical phase-sensitive amplifier with nonlinear Sagnac interferometer (NFSI-PSA) by both theoretical experimental study. In the theoretical study, parametric process within nonlinear fiber Sagnac interferomenter (NFSI) is described the small-signel analysis to obtain optical gain. The results of the small-signal analysis well explain experimental results, which means the analysis is applicable to design NFSI-PSA. We also confirmed as high as 11 dB gain increment by using high nonlinearity silica fiber which is enhanced nonlinearity parameter 7 times larger than the conventional single mode silica fiber.

Optical phase-sensitive amplifiers (PSAs) are promising as optical amplifier repeaters in fiber transmission system, because it has been shown theoretically that these have very low noise figures and waveform reshaping effect of chirped pulses. To realize in-line PSAs, the PSA requires internal light source generating pump light whose optical phase is locked to that of input signal light. The extended-ring cavity semiconductor laser with capability of frequency modulation and narrow linewidth-oscillation is developed as pump source and its optical phase is locked by two methods, optical signal injection and optical phase lock loop. By incorporating with degenerated parametric amplification in nonlinear fiber sagnac interferometer, in-line PSAs with internal phase-locked pump light source is successfully demonstrated.

位相感応型光増幅器(PSA)は、標準量子限界(NF=3dB)以下の低雑音性、変調不安定性の抑圧効果を有するため、中継器としての適用が期待できる。このPSAでは、励起光と信号光の光位相同期が必要であるが、従来実現されていなかった。光位相同期には光注入同期法と光位相同期ループ(光PLL)を用いる方法があるが、今回初めて光PLLにより信号光と励起光の光位相を同期させ、安定に光位相依存光増幅動作を実現したので報告する。

位相感応型光増幅器(PSA:Phase Sensitive Amplifier)は、無雑音で変調不安定性抑圧機能等があるため中継増幅器としての適用が期待できる。PSAを中継器として適用するためには、信号光に位相同期した励起光を用いることが必要であるが従来実現していなかった。光位相同期の達成には光位相同期ループを用いる方法と光注入同期法によるものがあるが、今回光注入同期により信号光に光位相同期した励起光を用いたPSA実験に初めて成功したので報告する。

The advent of erbium doped fiber amplifier achieved high-power and long regenerative repeater span optical transmission for high speed and long distance transmission systems. However, this simultaneously enhanced modulation instability originating from non-linear refractive index of transmission fiber. The signal-to-noise ratio (SNR) at receiver of NRZ optical transmission system tends to be degraded by modulation instability, especially for anomalous or zero dispersion fiber transmission systems. This study focuses on the application of phase-sensitive amplifier (PSA) as optical repeater in order to reduce modulation instability. Here, the SNR at receiver of PSA system was analyzed by including dispersion, dispersion slope, and non-linear refractive index of fiber. The results of these analyses indicate that PSA systems using zero dispersion fibercan effectively reduce modulation instability at the condition of high power optical transmission as high as 10 dBm.

The characteristics of phase-sensitive amplifiers using optical Kerr material in interferometer are investigated theoretically and experimentally. Relationship between phase dependent gain, saturation output power, bandwidth and parameters of optical Kerr material used in the phase-sensitive amplifiers is clarified theoretically. It is shown theoretically that the maximum gain of 26 dB, bandwidth of 95 GHz, 3 dB saturation output power of 0.33 W are achieved for standard dispersion shifted fibers (DSFs) with 1 W pump power. Experimentally, the gain characteristics of optical fiber-nonlinear loop mirror employing polarization maintaining DSF are measured. The gain up to 23 dB is obtained and gain saturation due to input signal light are confirmed for the first time. The possibility of suppressing noise by utilizing the gain saturation is discussed.

Reducing the degaradation of signal-to-noise ratio and of signal pulse form due to the combined effect of group velocity dispersion (GVD) and self-phase modulation (SPM) of transmission fiber is important issue to realize high-speend and long-span optical lightwave systems. In this report, the use of Phase-Sensitive Amplifiers as in-line repeater of the lightwave systems is theoretically studied to moderate those both of problems. In the discussion, higher order GVD and SPM are considerd to obtain the relationship between GVD, transmission speed and pulse shape limt, and then those results are compared between NRZ and RZ pulses. We also confirmed theoretically that the implementation of in-line PSAs expands regenarative repeater spacing about 10 times than that of EDFA systems, in case of TDM 40Gbit/s system.

入射光の位相に依存した利得を与える位相感応光増幅器(PSA:Phase Sensitive Amplifier)は、無雑音でかつチャープパルスの波形整形機能があるため中継増幅器としての適用が期待できる。今回、光カー効果を用いたPSAの基本特性について、理論的、実験的に検討したので報告する。

入射光の位相に依存した利得を与える位相感応光増幅器(PSA :Phase Sensitive Amplifier)は、無雑音[1]でかつチャープパルスの波形整形機能がある[2]ため中継増幅器としての適用が期待できる。今回、PSA多中継伝送系の最大再生中継間隔について理論的に検討し、初めて明らかにしたので報告する。

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