This PDF file contains the front matter associated with SPIE Proceedings Volume 7621, including the Title Page, Copyright information, Table of Contents, and the Conference Committee listing.

Some specific aspects of design, fabrication, application and characterization of selected waveguide devices for optical communication systems will be addressed in this paper ranging from familiar components like Bragg gratings to emerging devices exploiting stimulated Raman scattering in silicon. In particular, we will focus on fiber-optical and planar waveguide components for adaptive dispersion compensation, Raman-based amplifying and nonreciprocal devices in silicon and useful respective characterization techniques.

Optical transceivers are the dominating technology for the optical front end of short and medium reach optical communication systems. They are diverse, ranging from low cost and high volume applications to extreme performance and relatively low volume products. Different technical solutions for the optical components are used and this paper gives an overview of enabling technologies. Furthermore the challenges (density, power consumption, cost, reach, increased performance) that optical transceivers face today and which technologies may be used to solve these challenges in the future are discussed.

The infrastructure of the existing network is determined by the old copper access technology. Not only the copper access itself, also the number of central offices and their geographical distribution are results of the copper network and its physical limitations. Today, in Germany, several thousand active locations cater for the delivery of plain old telephony services, as well as for the delivery of new fiber-based broadband services. Due to the fact that the attenuation of optical fibers is relatively low, new concepts for the design of the network structure become possible and are discussed in this paper. A reach of 40 km, for example, on an optical transport system is no problem. Longer possible link lengths can result in a reduced number of central offices, leading to reduced expenditures for the building, power supply and air conditioning. In the case of Germany a number of some hundred central offices is envisaged. However, a significant drawback of today's existing optical access technologies is the very limited number of customers on a single fiber. For instance, GPON (Gigabit Passive Optical Network) provides typically a 32-way split and a distance of 20 km. This paper discusses some new ideas to introduce higher splitting ratios and longer access lengths into the network. With WDM (Wavelength Division Multiplexing) and/or coherent optical receivers new options for a future proof access network are available.

Fueled by the steady traffic increase in access and enterprise networks, optical metro networks represent a major growth opportunity for system vendors and component manufacturers. This paper reviews new developments from a technical and economic point of view. Topics such as network and node architectures, high-speed transmission, integrated optical/electronic switching as well as management and control will be discussed.

This paper describes the broadband situation in Japan and the recent development of optical metro networks, their future prospects and technologies. First, the situation as regards the broadband infrastructure and internet traffic in Japan is overviewed. Then, the recent development of reconfigurable optical add drop multiplexers (ROADMs) in optical metro networks is reviewed. Finally, the future prospects for optical metro networks are described with particular emphasis on 100Gbit/s standardization, sub-λ function, and colorless/directionless ROADMs.

A regenerative optical grooming switch for interconnecting 100 Gbit/s networks with lower bit-rate networks and switching functionality in time, space and wavelength domain is demonstrated. Lab and field demonstrations show the feasibility of the new concept. Q-factors above 20 dB are reported.

Tackling PMD has turned out to be one of the most puzzling problems during the advent of high speed optical transmission systems. It still seems far more attractive to avoid links with high PMD than to install an expensive PMDcompensator. Measuring the PMD of an installed fiber link can answer the question if this link can be operated with or without a PMD-compensator. Common test methods require exclusive access to the fiber link. This is considered to be a major limitation since it is not easy to reroute the traffic of a WDM system with many channels. This contribution discusses techniques to measure the PMD of a fiber link while it is in service ("In-Situ PMD Measurement"). These approaches can be applied to a single channel as well as to the whole received WDM signal and the fact that only single end access is needed makes them appear quite attractive. However, there are principal limitations which need to be understood in order to qualify a link. Performing these measurements while the link is in service will help network operators to smoothly upgrade to higher bit rates in their backbone networks.

A nonlinear optical loop mirror with a bidirectional attenuator has been used for regeneration of return-to-zero differential phase-shift-keyed (RZ-DPSK) signals. A 2.5 ps, 10 Gb/s signal with amplitude fluctuations of 28 % was regenerated with a negative power penalty of 2 dB practically back to the quality of the undistorted reference signal. Parameters limiting system performance and optimization possibilities will be discussed.

We present an optical receiver for RZ-DPSK signals that use photonic balancing. Photonic balancing is achieved through pulse counter-propagation and collision in a saturated SOA. We explain the principles of photonic balancing and show how it can lead to an improvement in RZ-DPSK detection by 3 dB, similar to electrical balancing. We also show how this scheme can be used as a Mamyshev-type regenerator.

Metro optical networks have undergone changes in design in recent years, driven by growing traffic demands and the establishment of new technologies driving network architectures. In this paper the drivers are described and the implications for optical amplifiers used in metro optical networks are discussed. Challenges for performance improvements and cost reduction in current networks driving metro amplifiers today, together with opportunities for future metro amplifiers are discussed.

A 2x2 cross/bar optically-driven switch is implemented with a single semiconductor optical amplifier. The switch exploits nonlinear polarization rotation experienced by two input signals in the amplifier in presence of a control pump light. The two input data signals travel in opposite directions inside the amplifier. In absence of the control light, the lowpower input signals do not experience nonlinear effects inside the amplifier; when the pump light is applied, both the input data signals experience cross-phase modulation, which reflects in nonlinear polarization rotation for the output signals due to polarization-dependent carriers modulation in the semiconductor amplifier. Polarizes are then used in the output paths in order to discriminate the output packets for the two possible cases of control pump signal in the ON and OFF state. Bit error rate measurements demonstrate error-free operation for both the possible switch configurations. By letting the input signals to travel the amplifier in opposite directions this architecture enables operation with data packets at the same wavelength. The switch speed is limited by the carriers recombination time in the amplifier, in the order of few hundreds of ps. Semiconductor technology allows implementation of compact, cost-effective, and low-power operating all-optical devices.

It has long been a goal of network planners to restructure their networks to reduce or eliminate fixed installations and all the operational difficulties and concerns that go along with them. Optical access networks have been a part of that goal because of their intrinsic long-distance capabilities. In practice, however, the demand for bandwidth has outpaced the supply offered by cost-effective passive optical systems. This has kept most PON deployments at a relatively modest reach (<20km) and split ratio (<32 way). Currently, NG-PON technologies such as 10 Gb/s systems, TDM, WDM, and their hybrids are coming on the scene. These potentially could increase the bandwidth capabilities on a single access fiber to many times what is practical now. The distance capabilities of these systems are also significantly improved, reaching to 60km. This may be the trigger for serious convergence of the inter-office/metro and access networks. This paper will examine the current trends in NG-PON technology, and extrapolate how these will impact the overall telecom network.

Steadily increasing customer demand for more and more bandwidth in excess of 100 Mbit/s per subscriber, new technical options and a strong competitive environment drive the evolution of today's telecommunication networks, particularly in the access network. The physical properties of fibers such as very low loss and almost unlimited bandwidth allow for high bit rate long distance transmission in future access networks compared to the conventional copper based access networks in place today. In future this is expected to lead to much larger service areas which are served from one central office and to a significant reduction of central offices of today's infrastructure facilitating a converged metro-access architecture. One driver for this network consolidation is the need for significant operational expenditure (OpEx) savings which are expected due to reduction of active equipment and footprint. But also the changes from today's "service oriented" network design, where each service is almost realized on a new platform, towards an open standardized multi-layer Next Generation Network where all services will be delivered over a common infrastructure will lead to significant challenges in the network infrastructure.

The increasing demand for higher bit rates in access networks requires fiber deployment closer to the subscriber resulting in fiber-to-the-home (FTTH) access networks. Besides higher access bit rates optical access network infrastructure and related technologies enable the network operator to establish larger service areas resulting in a simplified network structure with a lower number of network nodes. By changing the network structure network operators want to benefit from a changed network cost structure by decreasing in short and mid term the upfront investments for network equipment due to concentration effects as well as by reducing the energy costs due to a higher energy efficiency of large network sites housing a high amount of network equipment. In long term also savings in operational expenditures (OpEx) due to the closing of central office (CO) sites are expected. In this paper different architectures for optical access networks basing on state-of-the-art technology are analyzed with respect to network installation costs and power consumption in the context of access node consolidation. Network planning and dimensioning results are calculated for a realistic network scenario of Germany. All node consolidation scenarios are compared against a gigabit capable passive optical network (GPON) based FTTH access network operated from the conventional CO sites. The results show that a moderate reduction of the number of access nodes may be beneficial since in that case the capital expenditures (CapEx) do not rise extraordinarily and savings in OpEx related to the access nodes are expected. The total power consumption does not change significantly with decreasing number of access nodes but clustering effects enable a more energyefficient network operation and optimized power purchase order quantities leading to benefits in energy costs.

This paper investigates serial 100 Gbit/s PM-RZ-DQPSK transmission in the presence of perturbations from neighboring 10 Gbit/s NRZ, 40 Gbit/s RZ-DPSK, and 40 Gbit/s RZ-DQPSK DWDM channels. It addresses the need to outline upgrade paths of current hybrid DWDM systems equipped with 10 and 40 Gbit/s line cards towards 100 Gbit/s for remaining channels. A numerical simulation approach is used to evaluate the signal quality of the central probe for various DWDM channel constellations and power levels.

To simultaneously mitigate the linear and nonlinear channel impairments in high-speed optical communications, we propose the use of non-binary low-density-parity-check-coded modulation in combination with a coarse backpropagation method. By employing backpropagation, we reduce the memory in the channel and in return obtain significant reductions in the complexity of the channel equalizer which is exponentially proportional to the channel memory. We then compensate for the remaining channel distortions using forward error correction based on non-binary LDPC codes. We propose non-binary-LDPC-coded modulation scheme because, compared to bit-interleaved binary-LDPC-coded modulation scheme employing turbo equalization, the proposed scheme lowers the computational complexity and latency of the overall system while providing impressively larger coding gains.

The demand for 100 Gb/s optical links is rapidly spreading across all levels of the optical networking infrastructure. Many of the first deployments will be in the local area network (LAN) and metro-core and regional network environments. To address needs in LAN, the upcoming IEEE standard (IEEE P802.3ba) seeks 100 Gb/s over distances up to 40km. Furthermore metro-core/regional dense wavelength division multiplexing (DWDM) architectures require reach of several hundred km and the ability to pass through ten or more ROADMs. However, a number of fundamental challenges remain including the selection of appropriate modulation formats that are robust to a variety of nonlinearities, are sufficiently spectrally efficient, and able to withstand the strong optical filtering of cascaded ROADMs. Here we compare a variety of single-carrier quaternary modulation formats, each providing 2 bits/symbol/polarization and each likely to provide some advantages at 100Gb/s. Each format is presented with an appropriate MZM-based transmitter, and constrained by practical signal fidelity limitations that also enable comparison to experimental results from our 100G testbed. We primarily examine direct detection for cost-sensitive metro networks; however we also quantify the performance of coherent receivers, where applicable. Simulation results demonstrate the relative OSNR penalty (at a pre-FEC BER of 10^-3) for a range of launch powers and adjacent channel formats.

There have been numerous attempts to determine the channel capacity of a nonlinear fiber optics communication channel. The main approach, until recently, was to consider ASE noise as a predominant effect and to observe the fiber nonlinearities as the perturbation of linear case or as the multiplicative noise. In this invited paper, we describe how to determine the true fiber-optics channel capacity. Because in most of practical applications the channel input distribution is uniform, we also describe how to determine the uniform information capacity, which represents the lower bound on channel capacity. This method consists of two steps: 1) approximating probability density functions (PDFs) for energy of pulses, which is done by one of the following approaches: (a) evaluation of histograms, (b) instanton approach or (c) edgeworth expansion, and 2) estimating information capacities by applying a method originally proposed by Arnold and Pfitser.

This paper investigates DQPSK transport using both simulation and experimental results from our 100G testbed. We examine 56 Gb/s single polarization (single-pol) RZ-DQPSK and 112 Gb/s polarization multiplexing (POL-MUX) RZDQPSK with 12 Gb/s OOK aggressor channels and a variety of dispersion management maps using AllWave® zero water peak (ZWP) fiber. Although a number of studies of 40 Gb/s line rates within 10 Gb/s networks have been reported, there has been little with respect to 28 Gbaud DQPSK formats. We quantify the OSNR penalty due to nonlinearities of these hybrid optical links. Using a nominal span loss of 22 dB and different span lengths while keeping the dispersion compensation per span constant and the loss per span constant allows a direct examination of the impact of the residual dispersion per span (RDPS) on the nonlinear penalty in the DQPSK channel. We vary compensation from 90% - 110% (of total dispersion) across 8 spans (-119 ps/nm - +153 ps/nm). We report the required OSNR to achieve a non-FEC BER of 10^-4 versus RDPS for both single- and dual-polarization (dual-pol) RZ-DQPSK. Experimental data is validated against RSoft OptSim simulations.

In recent years, we have witnessed an increased demand on optical-networks transmission-capacities due to the growing popularity of the Internet and multimedia in everyday life. According to industry expert estimates, 1Tb/s-Ethernet should be standardized by the year 2012-2013. To this end, we propose a non-uniform modulation format that achieves the channel capacity for SNRs of up to 25dB. The proposed modulation format is optimized for ASE-noise-dominated channels and can achieve 400Gb/s data rate per polarization utilizing the currently-available components operating at 50-GSymbols/s. One major benefit of the current scheme is that it is an affordable upgrade to the current systems.

To open up new optical frequency resources available for optical communications, the concept of all-band photonics has been proposed, which is based on the utilization of broadband of optical frequencies in the 1-μm waveband as a novel photonic band for photonic transmission. In this study, an ultra-broadband photonic transport system was developed by employing a long-distance holey-fiber transmission line to simultaneously use the 1-μm waveband and a conventional waveband such as the C-band. We successfully demonstrate the use of a photonic transport system to achieve simultaneous 10-Gbps error-free optical data transmissions in the 1-μm waveband and C-band.

In recent years LDPC codes have gained significant interest in the area of optical communication systems due to their capacity-approaching performance, high coding gain and low decoding-complexity. We describe the construction principles of high-rate, high-girth, quasi-cyclic LDPC codes and present an LDPC-coded turbo equalization scheme suitable for simultaneous mitigation of multiple transmission impairments. The equalization scheme is based on the maximum a posteriori probability detection, based on Bahl Cocke Jelinek Raviv (BCJR) algorithm that employs the conditional density probability functions of the channel to calculate the initial log-likelihood ratios for the LDPC decoder. To optimize the code performance extrinsic information transfer charts are used. We then investigate and evaluate the performance of the proposed scheme in the presence of polarization mode dispersion (PMD), fiber nonlinearities and chromatic dispersion for 10 Giga symbols/s transmission system and various modulation formats including NRZ and polarization-multiplexed BPSK with both direct and coherent detection. LDPC codes of rates 0.8, 0.9 and 0.95 are evaluated. Experiments with and without chromatic dispersion compensation are conducted.

The still increasing demand for data bandwidth in short-haul transmission as well as in long- haul transmission implicates the development of optical high-speed communication systems that carry 40 Gbit/s and higher. This step is limited mainly by the polarization mode dispersion (PMD) of the fiber infrastructure. Direct detection transmission systems are state of the art. At this the square-law detection of the photo diode transforms linear distortions into nonlinear effects, which makes linear equalization principles less effective. Coherent detection on the other hand delivers amplitude, phase and polarization information of the field and thus enables advanced PMD-compensation in the electrical domain. We realize PMD-compensation by means of least mean squares based adaptive electronic equalizers. The drawback of adaptive equalization principles is the setting of the adaption step-size. Small step-sizes lead to very accurate results, but are very time-consuming. By contrast large step-sizes can accelerate the adaption process but lead to inaccurate equalizer settings. Accordingly, it is desirable to resize the step-size during the adaption process. For these reasons different step-size control algorithms are implemented, analyzed and adapted to the requirements of an optical PMD affected transmission system. It shows that step-size control algorithms are able to accelerate the adaption-process significantly.

There is no doubt that dispersion management soliton systems (DDMS) are the most applicable for the short-haul transport. However on practice it is unbelievable to realize an ideal coincidence between projected and installed lengths of dispersion map fibers, which can be explained, for example, by business problems or an optical closure placement. Here we present results of numerical simulations of optical pulse propagation and following bit-error-ratio estimation in a dense dispersion manage optical link with non-perfect dispersion maps.

A well-known dense dispersion management soliton (DDMS) technique is applied to increase bandwidth of metropolitan area network fiber optic links. This technique requires an installation of optical cables with dispersion compensating fibers (DCFs), which leads to high costs for upgrading of installed fiber optic links. To become the DDMS more applicable, we propose to place DCFs in optical fiber closures. Here results of numerical simulations of optical pulse propagation and following bit-error-ratio estimation in fiber optic link with DCFs in optical closures are represented.