This paper presents GMPLS/OXC networking experiments conducted in JGN II, a nationwide open test bed network established by NICT for promoting R&D activities of advanced networking technologies and network-related applications. This paper describes experimental results that show improvement in the operability of OXCs that are provided connection policy control at the user network interface. The results also show the feasibility of customer controllable functions based on NMS, and the interworking between MPLS and GMPLS using a broadband application. The experimental results confirm the feasibility and applicability of GMPLS/OXC.

Optical fiber transport networks have been evolving rapidly to meet the demands of today's telecommunications such as unprecedented transmission capacity and reach. Fiber nonlinearity becomes an important issue as the transmission capacity and reach increase, and appropriate management of fiber nonlinearity is necessary. We review the progresses on some novel techniques for managing fiber nonlinearity in modern optical transmission systems. Advanced optical modulation techniques that allow optical signals to have high tolerance to both inter-channel and intra-channel nonlinear effects will be discussed. In particular, differential phase-shift keying (DPSK) and its impact in high-speed dense wavelength-division-multiplexing (DWDM) systems will be described. Novel dispersion management methods that suppress nonlinear effects will also be reviewed, particularly in the context of scalable and transparent optical transport networks having mixed 10 Gb/s and 40 Gb/s DWDM channels and optical add/drop multipliers (OADM). Electronic techniques that compensate for fiber nonlinearity at the transmitter side and the receiver side will be briefly discussed.

High-speed optical transmission systems operating at 40 Gb/s or higher are severely limited by intrachannel nonlinearities such as intrachannel four-wave mixing (IFWM) and intrachannel cross-phase modulation (IXPM). Approaches to deal with intrachannel nonlinearities may be classified into three broad categories: modulation formats, constrained (or line) coding, and equalization techniques. The IFWM is a phase-sensitive effect, and the aim of the first approach is to remove the phase short-term coherence of the pulses emitted in a given neighborhood. The role of constrained coding is to avoid those waveforms in the transmitted signal that are most likely to be received incorrectly. In this paper we describe two alternative techniques for suppression of intrachannel nolinearities: (i) constrained coding techniques, and (ii) combined nonlinear ISI cancellation and error control. Three different constrained coding techniques will be presented: (a) the use of constrained encoding itself, (b) combined constrained and error control coding and (c) deliberate error insertion. The nonlinear ISI cancellation scheme employs the maximum a posteriori probability (MAP) symbol decoding based on Bahl-Cocke-Jelinek-Raviv (BCJR) algorithm, while the forward error correction is based on low-density parity-check (LDPC) codes. The nonlinear ISI channel is modeled by a finite state machine (FSM) whose transition and output functions describe the dependency of the channel statistics and the ISI on transmitted patterns. The BCJR algorithm operates on a trellis of the corresponding FSM, and creates the soft information (detected bit likelihoods) used in the iterative decoder. To improve the BER performance of nonlinear BCJR equalizer further, a noise-predictive BCJR equalizer is introduced. The main feature of these schemes is that they can operate in the regime of very strong intrachannel nonlinearities where FEC schemes such as turbo or LDPC codes are not designed to operate.

Parametric devices based on four-wave mixing in fibers enable the amplification, frequency conversion and phase conjugation of optical signals. In this paper some recent research on parametric devices is reviewed briefly.

With the increasing technical maturity in fiber, wireless and satellite communication technologies, new horizons are becoming feasible for future broadband networks, providing economical data rates well in excess of Gbps for stationary and mobile users as well as novel applications these advanced network services will permit. This talk explores the future architecture possibilities of such a network using new and radical technology building blocks such as: free space laser communications, multiple access multi-beam data satellite communications, novel all-optical network transport/switching and analog transmission and processing over optical carriers that support coherent distributed platform sensing and communications. We will articulate why we have to design this new network across layers from the Physical Layer to the Network and Transport Layers (even the Application Layer). Not only can future network performance and cost undergo quantum-leap improvements; such a network can have profound transforming effects on space and terrestrial system architectures for sensing, healthcare, early warning systems, disaster relief, research collaborations and other new commercial applications.

Optical networking attracted a lot of interest in the telecommunication industry during the late 1990s. This interest has weakened since the downturn of this industry in 2000-2001 and throughout the post bubble years. Today, there are signs that optical networking is coming back. In this paper, we examine the current status of optical networking and switching, in terms of deployment in communication networks. We provide a status update in the telecommunication and cable industries. We also discuss today's trend toward relying on optical networks in advanced research and education (R&E) networking initiatives.

There are an increasing number of ways optical network devices and IP routers can interact with each other during a network fault. To provide continuity of service, the interactions between each component in a network must be cooperative. Consequently, the effect of recovery processes cooperating are the network configurations that have certain structural relationships, which can be elaborated. A conflict detector can prove that service will be restored during a fault scenario by checking whether these structural properties hold. We are using simulation as a method to study the coordination of recovery strategies and whether different coordination strategies will achieve recovery goals attached to a network service. The network service carries a traffic stream, which is injected into and extracted from a network. For multilayer recovery to complete, the cumulative effect of device actions during a failure must be (1) a connected path between the endpoints of a service and (2) a flow traffic delivered to a destination at a quality that matches a service level agreement. We represent Optical and Multiprotocol Label Switching (MPLS) recovery actions as graph-maintenance operations that change the state of a digraph. For example, the actions of forwarding traffic between an access port and a trunk port and selecting traffic from a new trunk port and forwarding it to an access port can be modeled as a sequence of edge additions and deletions. The state of the digraph represents the current configuration of a multilayer network as actions of recovery are performed. In this paper, we define some structural properties that can be observed during a simulation as the network evolves to a final state from an initial state before a failure occurs.

This paper proposes new switch architectures for hierarchical optical path cross-connect (HOXC) systems. The architectures allow incremental expansion of system scale in terms of the number of input/output fiber ports, wavebands, and optical paths per waveband. These feature assure the cost-effective introduction of the HOXCs even at the outset when traffic volume is not so large. Furthermore the effectiveness of the proposed switch architectures is demonstrated in a comparison with single-layer OXCs (conventional OXCs). The results provide useful criteria for the introduction of HOXCs.

This paper reviews the ROADM technologies and their applications in practical networks. The review is based on a system integration point of view, and points out the economics challenges of today's ROADM technologies.

In today's converged network environment, a rapid transition to unified packet-based core/edge network architecture is occurring. Core architecture becomes a two-layer network structure based on IP/MPLS (Internet Protocol/Multi-Protocol Label Switch) transport over DWDM bandwidth pipes, which is the most effective way of providing sharing network capacities, enabling efficient protection schemes, and delivering guaranteed end-to-end performance. The edge network is recognized as a place for an intense manipulation of both data streams and services, through traffic grooming, exchange, and service convergence. Three major groups of the end-to-end services are voice, data, and video. Today's reality is that current network structure is in transitional phase, where a number of legacy services, delivering voice and data, are still in place, while packet based services are being rapidly introduced. Optical ROADM handles the wavelength bandwidth pipes and provides flexible handling of wavelength paths (amplification, add/drop, and wavelength switching). In-service upgrade should be achievable at any particular location, which means that in line-amplifier site can be converted to ROADM site. In addition, the ROADM site should be upgradeable to full wavelength crossconnect functionality, which is required in a number of application scenarios. The ROADM functionality is not limited to wavelength related functions, but rather handles the key functions related to multiservice environment by accommodating Layer 1&2 features from a blade. Herewith, we will analyze the role of ROADM, its functions, and expansion over cross-layer applications, and present a structure that is the most appropriate to multiservice packetized environment.

In spite of its long term promise, all-optical switching is still plagued by high cost, low efficiency when handling bursty data traffic, immature management and protection and poor output port contention resolution leading to heavy loss. Given the current situation, hybrid approaches that keep the best features of optics, reverting to the electrical plane when expedient, constitute sensible interim steps that can offer cost-effective solutions along the road to an eventual all-optical core. Two such approaches developed in the framework of the European IP project NOBEL are presented in this work. The first is a quite mature solution that extends present day concepts to achieve multiplexing gain while keeping all the management and restoration benefits of SDH. The other mimics early LANs in executing a distributed switching via its electrical control plane using two-way reservations, thus restricting its applicability to smaller domains. Combining the two leads to a system fulfilling most of today's requirements for Tb/s core networks.

The prospects of deploying Optical Burst Switching (OBS) in next generation all-optical transport networks would greatly benefit, in terms of ease of implementation and cost, from reducing or even avoiding the use of wavelength converters at the network nodes. This paper presents a performance evaluation of strategies to minimize wavelength contention in OBS networks by optimizing wavelength assignment at the bursts ingress nodes. A new wavelength contention minimization strategy is proposed and shown to outperform a previously proposed strategy, in some cases by several orders of magnitude in terms of average burst blocking probability. A tighter performance bound for these strategies is also proposed. Moreover, the network conditions that enhance the effectiveness of using these strategies in OBS networks without wavelength converters are also discussed.

In this tutorial paper, we compare performance of several classes of forward error correction schemes suitable for advanced optical transmission. The first class is based on the concatenation of two RS codes. The second class is based on turbo product codes with BCH codes as component codes. The third class is based on low-density parity-check (LDPC) codes that have attracted much attention over the past decade. The fourth class of codes to be presented is generalization of both turbo product and LDPC codes, known as generalized LDPC (GDLPC) codes. To increase the coding gain while keeping the codeword length reasonable low, the class of nonbinary LDPC codes is introduced. A sophisticated simulator that models all major transmission impairments is used to assess the performance of the error correction schemes.

In this paper an error correcting scheme for long-haul optical transmission systems based on the maximum likelihood sequence detection-Viterbi algorithm and a hard decision "Gallager B" decoding algorithm for LDPC codes is proposed. Numerical results for various LDPC codes are presented and it is shown that the proposed method provides significant coding gain with respect to the uncoded system and Viterbi equalizer only.

As is well known, chromatic dispersion (CD) and nonlinear effect such as self-phase modulation (SPM), cross-phase-modulation (XPM), and four-wave-mixing (FWM), as well as their impairments interaction with each other are recognized as a limiting impairment for a high bit rates optical systems. With the advent of the 40 Gb/s, it is necessary to study transmission performance, which clearly depends on the modulation format and the system design. A numerical comparison of non-return-to-zero (NRZ), return-to-zero (RZ) and differential phase shift keying (DPSK) formats is made at a bit rate of 40 Gbit/s for single-channel and WDM systems with different compensation method in attempt to find the optimum modulation format. The transmitter under consideration used a 1.5 um DFB-laser externally modulated by a MZM modulator with modulation format (NRZ, RZ, DPSK), 64 PRBS data. At the receiver end an optical filtering using gaussian, fabry-perot and rectangular filter is used. Between the compensation method the symmetrical design leaves the best results in comparison to pre- and post-compensation. The impact of SPM can be reduced considerably by the symmetrical design. NRZ shows a best toleranz again chromatic dispersion and DPSK a best toleranz to Nonlinearity.

In high bit-rate return-to-zero (RZ) on-off keying (OOK) systems operating at 40Gb/s and beyond ghost pulses induced by intrachannel four-wave mixing (IFWM), and intrachannel cross-phase modulation (IXPM) are dominant factors affecting the performance of a high-speed optical transmission system. As the creation of ghost pulses is a phase sensitive effect, the common approach to deal with IFWM is to remove short-term phase coherence by employing a proper modulation format. Another approach, known as constrained or line coding, is to identify the most troublesome sequences and to forbid them during encoding process. This paper presents an efficient method for testing the efficiency of a modulation techniques for countering the effects of IFWM by calculating the sum of all the contributors at a given resonance position. For a modulation technique to counter these effects the initial pulses phases must be chosen properly so that different contributors to the ghost pulse creation cancel each other in bit being in "resonance". In addition to this method, we are proposing a modulation technique that shows a significant Q-factor improvement of up to 7.5dB (depending on the number of spans and the phase sequence implemented) over the uncoded RZ-OOK as will be demonstrated. Finally, implementation of this phase modulation technique is very efficient in extending the non-linearity tolerance and enhancing the performance of a high-speed optical transmission system.

This article presents, for the first time, the derivation of approximate analytical formulae for the probability density function and the cumulative density function of the optical signal-to-noise ratio variation in optical local and metropolitan area networks due to the weakly polarization-dependent gain of cascaded semiconductor optical amplifiers. The cumulative density function is used to calculate the outage probability and derive specifications for the maximum allowable value of polarization-dependent gain per semiconductor optical amplifier in order to achieve a given network size.

The most common model used for PMD simulations visualizes the fiber as a concatenation of a large number of birefringent elements. This system's DGD has the same Maxwellian PDF for each frequency. By measurement of certain links it is shown that the PDF of the DGD is not equal for all of the frequency bands. This behavior could be traced back to the fact that fiber links consist of a certain number of stable buried sections, with nearly no PMD changes over weeks and months. These sections are connected by sections exposed to strong temperature variations, acting as polarization rotators. This new model of a fiber link is known as the hinge model. To characterize these hinges, the temperature dependent behavior of several DCM and patch cords commonly used in WDM systems have been investigated. Measurements showed that DCM are the most active hinges. They produce approximately a full rotation in Stokes space when heated 1°C. This rotation is both reproducible and reversible. An novel model of the analyzed DCM has been developed in Matlab, which is able to reproduce the described measured behavior in simulations. The frequency dependency of the DGD's PDF leads from overall systems outage probability to frequency selective outage probability. That means instead of having a system outage at a certain outage probability, outage probabilities are connected to a number of outage channels.

Polarization mode dispersion (PMD) is one of the major limitations for optical transmission systems at 10 Gb/s and beyond. While first- or second-order PMD compensators (PMDC) can be driven with a feedback signal, more complex broadband PMDCs have to be set feed forward. An exact knowledge of the fiber's PMD characteristics - e.g. the PMD vector - is needed for the feed forward setting. Since PMD changes with time, real-time PMD measurement without data traffic interruption is necessary. Some recently published frequency- and time-domain methods meet these conditions. In this publication we are going to examine and compare different on-line measurement methods. Using numerical simulations, the performance of the measurement methods is assessed in terms of the accuracy of the PMD vector measurement and the qualification as feed forward control signal for setting a PMDC. The measurements exhibit an inherent inaccuracy if the signal is launched close to one of the principal states of polarization (PSP). Although these combinations of PSP and signal polarization result in inaccurate PMD vector measurements, the transmitted signal is not degraded by first order PMD. Consequently, the accuracy of the PMD vector measurement is a bad figure of merit for the performance of a system including a feed-forward set PMDC. Furthermore, due to the averaging over the signal bandwidth, the measured PMD vector is a better control variable for a PMDC than the analytically calculated PMD vector if second order PMD is considered.

Driven by high growth rates of internet traffic the question of upgrading existing optical metro-, regio- and long haul transport networks introducing 40 Gbit/s/λ is one of the most important questions today and in the near future. Current WDM Systems in photonic networks are commonly operated at linerates of 2.5 and 10 Gbit/s/λ. Induced by market analyses and the historical development of transport systems some work has already been carried out to evaluate update scenarios from 10 to 40 Gbit/s channel data rates. Due to the inherent quadruplication of the bandwidth per channel, limitations due to linear and non-linear transmission impairments become stronger resulting in a highly increased complexity of link engineering, potentially increasing the capital and operational expenditures. A lot of work is therefore in progress, which targets at the relaxation of constraints for 40 Gbit/s transmission to find the most efficient upgrade strategies. One approach towards an increased robustness against signal distortions is the introduction of more advanced modulation formats. Different modulation schemes show strongly different optical WDM transmission characteristics. The choice of the appropriate format does not only depend on the technical requirements, but also on economical considerations as an increased transmitter- and receiver-complexity will drive the transponder price. This article presents investigations on different modulation formats for the upgrade of existing metro-/ regio and long haul transport networks. Tolerances and robustness against the main degrading effects dispersion, noise and nonlinearities are considered together with mitigation strategies like the adaptation of dispersion maps. Results from numerical simulations are provided for some of the most promising modulation formats like NRZ, RZ, CS-RZ, Optical Duobinary and DPSK.

All-optical multi-casting permits the establishment of high-quality, high-bandwidth point-to-multipoint applications in metropolitan area networks by diffusing an incoming data carrying wavelength onto a number of outgoing wavelengths. With the proliferation of hybrid Wavelength Division Multiplex (WDM)/Optical Time Division Multiplex (OTDM) networks, the ability to perform high-speed broadcasting of OTDM signals at multiple wavelengths will prove an efficient method in the dissemination of information over WDM. Current approaches to WDM multi-casting involve the execution of multiple cycles of optical-electronic-optical conversion, thus necessitating the use of costly high-speed electronics and optoelectronics. All-optical multi-casting would therefore remove such constraints while concurrently providing for a higher level of network transparency thereby improving network management and performance. To date, the issue has most promisingly been addressed through the manipulation of nonlinear phenomena within semiconductor optical amplifiers (SOA). The demonstrations so far however, have exhibited either low conversion efficiency or operating speed constraint or a complicated setup. All-optical Mach-Zehnder interferometer (MZI) approaches are therefore particularly attractive as they are not limited by the aforementioned constraints, while still offering a low switching power requirement at high-speed and a high level of integratability. In this paper we present a detailed model replicating a 40Gb/s experimental setup in order to investigate the operational limit of the MZI when employed in WDM multi-casting. Through simulation we examine the factors determining the constraints imposed on the maximum number of output multi-cast channels that can be achieved using such a device and establish its suitability as a next-generation all-optical multi-caster.

In this tutorial, we will show several novel optical instruments using optical phase modulation, which is a common technique used in fiber optic communications for phase shift keying and chirped RZ transmission. We will cover the concept of space-time duality, time-lens for jitter compensation and pulse compression, time-prism for ultrafast tunable optical delay, and generation of effective negative nonlinear refractive index using electro-optic phase modulation for compensation of self-phase modulation. These device concepts are inspired by the rapid technological development in telecom, and demonstrate the great potential of applying telecom technologies to optical instrumentation.

Optical multiplexers/demultiplexers developed for the telecommunication industry, at the level of the basic principles, perform essentially the same functions as general-use optical spectrometers. The spectrometer design inspired by the telecom devices would represent an extremely compact device compatible with the manufacturing procedures in integrated optoelectronics and micro-optics. In this paper we summarize our recent results on development of a miniature optical spectrometer. The spectrometer uses a diffractive optical element integrated with a planar optical waveguide. It is designed to provide spectral resolution of at least 2nm in the entire visible spectral range from 400nm- 700nm, and simultaneously resolve spectra from up to 35 independent optical inputs. The optical part of the spectrometer fits volume below 10mm³. The spectrometer is designed for on-chip diagnostic systems, in particular for fluorescence detection of hazardous materials. A device prototype with diffractive optical element fabricated using electron beam lithography is manufactured and tested.

The effects of optical feedback on the magnitude of the anticorrelation of polarization dynamics in vertical-cavity surface-emitting lasers have been studied experimentally. We compare the effects of polarization-preserved and polarization-selective optical feedback on the magnitude of the anti-correlation. The results show that in the case of the polarization-preserved or orthogonal polarization optical feedback into the VCSEL a strong anti-correlation between orthogonal polarizations can arise, however, no strong anticorrelation is observed for parallel polarization optical feedback. The correlations in the spectral domain have also been investigated. It is found that the anticorrelation is strong at low frequencies but poor at higher frequencies.

Explicit expressions are derived for the like and cross linear polarized reflection and transmission coefficients in terms of the chiral parameter. Taylor series expansions of these coefficients are derived. The diagonal like polarized reflection and transmission coefficients are insensitive to the chiral properties of the material while the off diagonal cross polarized terms are proportional to the chiral parameter to first order. Continuity relations in and perpendicular to the plane of incidence for vertically and horizontally like and cross polarized waves, energy conservation and duality relations at a free space-chiral interface are satisfied. Applications for the optimal detection and identification of chiral materials such as drugs and biological or chemical threat agents are considered.

All-optical XOR operation has been demonstrated using a semiconductor optical amplifier Mach-Zehnder interferometer (SOA-MZI) and delayed interferometer (DI) at 80 Gb/s. The DI is based on a polarization maintaining loop mirror (PML). The results show using the PML-DI to perform differential scheme can improve the pulse quality of the XOR result.

An analytical approach is presented to evaluate the impact of polarization mode dispersion on the average bit error rate (BER) performance of an intensity modulated direct detection (IM-DD) optical transmission system considering Maxwellian distribution for the differential group delay (DGD). The results show that the performance of an IM-DD system suffers power penalty of 0.27 dB, 0.45 dB and 2.4 dB corresponding to mean DGD of 20 ps, 35 ps and 40 ps respectively at a BER of 10^-9 operating at a bit rate of 10 Gb/s. Furthermore, at increased values of the mean DGD there occur BER floors above 10^-9 which can not be lowered by further increasing the signal power. It is noticed that BER floors occur at about 2x10^-9, 10^-7 and 10^-5 corresponding to mean DGD of 45 ps, 50 ps and 60 ps respectively at 10Gb/s. The effect of PMD is found to be more detrimental at higher bit rates.