This PDF file contains the front matter associated with SPIE Proceedings Volume 6774, including the Title Page, Copyright information, Table of Contents, Introduction (if any), and the Conference Committee listing.

This paper describes the photonics technologies that make it possible to support exploding traffic demand in next generation broadband networks combining telecom and broadcast arena. Technology trends of high capacity transmission and network node are summarized including some Japanese government funded projects, together with access technologies and some emerging device technologies that support the system requirements.

Due to the tenfold capacity increase of Ethernet from one generation to the next, 100 Gbps will be the straight forward next step after 10 Gbps. Demand can be predicted for the following years based on increasing internet data traffic and the lack of efficient packet based link aggregation mechanisms in the Ethernet protocol. Solutions have to be found for short haul intra-office and long haul inter-office interconnections of large routers. This contribution focuses on options for physical layer interfaces. Optical component aspects are discussed as well as transmission aspects. The selection of a suitable modulation format in combination with equalizer technologies opens a path towards robust transmission systems for this ultra-high datarate.

The future Internet traffic growth will require deployment of optical transmission systems with bit rates higher than rate of currently available 40-Gb/s systems, such as 100-Gb/s and above. However, at data rates beyond 100-Gb/s the signal quality is significantly degraded mainly due to impact of polarization mode dispersion (PMD), and intra-channel nonlinear effects. All electrically time-division multiplexed (ETDM) multiplexers and de-multiplexers operating at ~100-Gb/s are becoming commercially available. However, the modulators operating ~100-Gb/s are not widely available so that alternative approaches to enable 100-Gb/s transmission and beyond using commercially available components operating at 40-Gb/s are of high practical importance. In this invited paper, several joint coded-modulation and multiplexing schemes enabling beyond 100-Gb/s transmission using commercially available components operating at 40-Gb/s are presented. Using this approach, modulation, coding and multiplexing are performed in a unified fashion so that, effectively, the transmission, signal processing, detection and decoding are done at much lower symbol rates, where dealing with the nonlinear effects and PMD is more manageable, while the aggregate data rate is maintained above 100-Gb/s. The main elements of our approach include: (i) bit-interleaved LDPC-coded modulation, (ii) multilevel coding (MLC) with LPDC component codes, and (iii) LDPC-coded orthogonal frequency division multiplexing (OFDM). The modulation formats of interest in this paper are M-ary quadrature-amplitude modulation (QAM) and Mary phase-shift keying (PSK), where M=2,...,16, both combined with either Gray or natural mapping rule. It will be shown that coherent detection schemes significantly outperform direct detection ones and provide an additional margin that can be used either for longer transmission distances or for application in an all-optical networks.

A key challenge set by carriers for 40Gb/s deployments was that the 40Gb/s wavelengths should be deployable over existing 10Gb/s DWDM systems, using 10Gb/s link engineering design rules. Typical 10Gb/s link engineering rules are: 1. Polarization Mode Dispersion (PMD) tolerance of 10ps (mean); 2. Chromatic Dispersion (CD) tolerance of ±700ps/nm; 3. Operation at 50GHz channel spacing, including transit through multiple cascaded [R]OADMs; 4. Optical reach up to 2,000km. By using a combination of advanced modulation formats and adaptive dispersion compensation (technologies rarely seen at 10Gb/s outside of the submarine systems space), vendors did respond to the challenge and broadly met this requirement. As we now start to explore feasible technologies for 100Gb/s optical transport, driven by 100GE port availability on core IP routers, the carrier challenge remains the same. 100Gb/s links should be deployable over existing 10Gb/s DWDM systems using 10Gb/s link engineering rules (as listed above). To meet this challenge, optical transport technology must evolve to yet another level of complexity/maturity in both modulation formats and adaptive compensation techniques. Many clues as to how this might be achieved can be gained by first studying sister telecommunications industries, e.g. satellite (QPSK, QAM, LDCP FEC codes), wireless (advanced DSP, MSK), HDTV (TCM), etc. The optical industry is not a pioneer of new ideas in modulation schemes and coding theory, we will always be followers. However, we do have the responsibility of developing the highest capacity "modems" on the planet to carry the core backbone traffic of the Internet. As such, the key to our success will be to analyze the pros and cons of advanced modulation/coding techniques and balance this with the practical limitations of high speed electronics processing speed and the challenges of real world optical layer impairments. This invited paper will present a view on what advanced technologies are likely candidates to support 100GE optical IP transport over existing 10Gb/s DWDM systems, using 10Gb/s link engineering rules.

Improving the tolerance to polarization mode dispersion (PMD) is considered to be one of the major prerequisites for the success of modern high bit rate optical communication systems. Various approaches such as optical compensation, electrical mitigation, multi-level modulation formats promise to increase the PMD tolerance of optical systems, whereas the question of how to experimentally characterize these solutions needs to be answered before commercial deployment. This is not an easy task since these systems need to be characterized with respect to first and higher order PMD but also with respect to their dynamic behavior. We show that deterministic polarization controllers combined with in-situ measurement of PMD can help to explore the PMD tolerance of an optical communication system and to generate reliable and repeatable results by avoiding statistical elements such as polarization scramblers. These elements can be combined to form a PMD testbed which allows to stress a system by applying a deterministic amount of PMD including a well-defined rate of change. Such a PMD testbed can be used during development of adaptive mitigators as well as for compliance testing. Finding an agreement on standard test procedures for such a testbed will make the evaluation of PMD tolerant receivers easier and more comparable.

Due to the growing demand of bandwidth in optical communication systems, the step towards 40 Gbit/s is inevitable. This step is limited mainly by the polarization mode dispersion of the fiber infrastructure. To extend the usability of the infrastructure it is necessary to employ PMD-compensation. The On/Off-keying modulation format in conjunction with direct detection is state of the art in high bitrate optical communication systems. But as a drawback, direct detection only provides an output signal which is proportional to the square of the absolute value of the electrical field and therefore transforms linear effects such as PMD into the nonlinear domain, which makes linear compensation schemes 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. In our work, we employ optical coherent detection to receive two orthogonal components of the complex valued electrical field of an On/Off-keying modulated optical carrier. This single input multiple output system delivers us up to four output signals, i.e. real and imaginary part of the two detected polarization planes, which can be fed to feed forward equalizers or other electronic processing methods for an effective compensation of signal distortions caused by PMD. The required feed forward equalizer settings and their performance are presented.

Ethernet is widely used in LAN and campus networks and its potential use for next generation transmission systems is further supported by ongoing standardization activities for 100Gb/s Ethernet over optical fiber. In telecom networks data rates of 40Gb/s per channel will be deployed during the next few years and discussions about the next option already started. To ensure compatibility and foster the transport of Ethernet data the upgrade to 100Gb/s optical transmission in telecom networks is under discussion. Several transmission techniques like advanced modulation formats (e.g. DQPSK), inverse Multiplexing, OFDM and equalization techniques are possible candidates. As high speed electronics become available pure 100Gb/s ETDM seems to be the most cost efficient solution, compared to polarization multiplex or multilevel modulation, but suffers from severe signal degradations due to chromatic dispersion and even dispersion slope. As these effects are also temperature varying the adaptive dispersion compensation is critical for 100Gb/s systems. The variations of first and second order dispersion for the SMF as well as the DCF modules have to be compensated exactly and therefore adaptive techniques are mandatory. In this paper we investigate the influence of dispersion changes due to temperature variations in 107Gbit/s transmission for different system configurations consisting of e.g. transmission fibers like SSMF and NZ-DSF and appropriate DCF modules by numerical simulations. The temperature and dispersion variations are changed randomly for different fiber spans to model a distributed telecom infrastructure of regional and metro networks. The potential of optical and electrical equalizers in these scenarios using cost-effective NRZ modulation is analyzed.

A theoretical analysis for evaluating the performance of a lincoded continuous phase optical frequency shift keying (CPFSK) optical transmission system impaired by polarization mode dispersion (PMD) with delay line demodulation receiver is presented. The analysis is carried out for three different linecoding schemes, i.e., alternate mark inversion, order-1 and delay modulation coding, to investigate the efficacy of the linecoding in counteracting the effect of PMD in CPFSK optical transmission system. The average bit error rate (BER) performance results are evaluated with line codes and compared with NRZ-CPFSK system at a bit rate of 10 Gb/s considering Maxwellian probability distribution for the mean differential group delay (DGD) due to PMD. The results show that the penalty improvement of line coded systems is within 0.5 dB to 2.0 dB with respect to NRZ data at a BER of 10^-9.

Future transparent networks require optical regeneration. The regeneration process of amplitude-modulated signals consists of three key stages: re-amplification, re-shaping, and re-timing. In this Paper we briefly review various optical clock recovery methods and propose a polarization insensitive low-cost scheme capable of resolving timing information simultaneously for multiple wavelength channels. We also discuss the prospects of low-cost volume production with integrated optics and especially with Si-photonics.

Sophisticated modulation formats like phase shift keying (PSK) as discussed for high-speed fiber-optic transmission systems operating at 40 Gbit/s and beyond, cause new challenges for clock recovery. Whereas conventional return-to-zero on-off keyed (RZ-OOK) modulated signals provide proper clock tones which can be used to recover the clock signal, the additional phase modulation (RZ-PSK) changes the spectral composition of the signal and weakens or suppresses the clock tones. This effect is bit pattern dependent as can be seen from a simple example: If all the pulses in an RZ-PSK signal are in phase, the result is equivalent to an ordinary RZ on-off-keying (OOK) signal with a strong carrier and clock tones. If the pulses in a sequence oscillate in phase by &pgr;, the result is equivalent to the well-known carrier-suppressed return-to-zero signal (CS-RZ) where the carrier is suppressed and where clock tones are differently spaced compared to RZ-OOK. In this paper we present results of the simulation of the different cases taking into account realistic bit sequences and analyze the results with special emphasis on the influence the effect has on clock recovery.

The increasing demand for higher transmission capacity originated by upcoming Triple-Play services forces the network operators to increase the transmission capacity and drive down the costs per bit/s. Therefore the line rates of installed networks, operating at 2.5 and 10 Gbit/s/λ, must be upgraded. In current optical networks first implementations of WDM Systems with line rates of 40 Gbit/s/λ are already accomplished. First results with electronically multiplexed transmitters and receivers at 80 Gbit/s/λ have already been published and higher channel data rates e.g. 100 or 160 Gbit/s/λ attract more and more attention in the R&D community. With increasing data rates unfortunately new circumstances and physical impairments have to be considered, which are negligible at lower data rates. For data rates above 40 Gbit/s chromatic dispersion causes pulses to broaden extremely rapidly, so that transmission behaviour can be regarded as "quasi-linear". Due to the broad signal spectra and massive pulse overlap the signal quality is mainly degraded by the intra-channel effects intra-channel-cross-phase modulation (IXPM) and Intra-channel four wave mixing (IFWM). In this paper we present an analytic engineering rule to extend the system reach limits for 160 Gbit/s/λ data rates by optimizing the dispersion compensation schemes for different parameters such as fiber types and modulation formats. With minimizing the effect of non-linear intra-channel crosstalk, by able system design the maximum system reach can be extended by more than 40%.

Good resource allocation strategy is able to alleviate the resource contention. Deflection routing is one of contention resolution of good connectivity optical burst switching networks. But the offset time maybe not enough for reserve resource if deflection routing adopted. Too much deflection adopted will deteriorate the network performance, another issue is how to determine if a contending burst will be deflected or discarded. In this paper, little Fiber Delay Lines (FDL) is used to assure the offset time will be compensated in time, and an optimum scheme is proposed from three aspects as if the network situation permits deflection, if contending burst is worthy to be hold continuously and the impaction of alternative route on deflection. Numerical results show that our optimized deflection scheme can achieve not only preferred deflection, but also to keep wavelength link from overloading. It balances the network load and stabilizes the network performance some degree.