We present real-time polarization mode dispersion (PMD) tolerance measurement results with a commercially available 500 Gb/s coherent modem. The first- and second-order PMD space is explored, showing that peak values of 500 ps of static, first-order PMD (differential group delay) have small penalties. The system was stressed using fast scrambling, with polarization change of over 10 000 rad/s, along with high mean PMD. Penalties were small with sufficient equalization.

As traffic demands continue to grow, supporting data rates beyond 100 Gb/s will be required to increase optical channel capacity and support higher-rate client interfaces. Advanced modulation formats that adapt to optimize spectral efficiency over a range of channel signal-tonoise ratio conditions are required. Channels can be constructed by varying parameters such as symbol rate, bits per symbol, number of polarizations, and number of optical and electrical subcarriers. Channel capacity can also be increased using advanced techniques such as optical time-division multiplexing, and fibers that support multiple cores and modes. Many channel designs can support higher data rates, but there are trade-offs between complexity, spectral efficiency, and optical reach.

Nonlinear refraction in fiber optic links is a capacity limiting mechanism, whereby the phase of each propagating signal is modulated by intensity variations of signals in nearby channels. The transition to coherent detection enables a wide variety of modulation formats to be considered. Indeed, the choice of modulation format plays a primary role in determining the degree of amplitude variation in the channel as well as the robustness to the phase noise impairment that nonlinearities induce. On one hand, constant envelope formats (or nearly-constant) avoid fluctuations in the signal and produce lower nonlinearity-based impairments. Alternatively, star-QAM modulation formats enhance the receiver's robustness to phase noise. Using simulated and experimental results we demonstrate the effectiveness of each format in avoiding fiber nonlinearity effects for both standard fiber (17ps/nm-km) and NZDF (5 ps/nm-km). We show sensitivity of several formats to nonlinear phase modulation from adjacent channels. We show the interaction between dispersion and constant envelope formats that guides the applications in which constant envelope formats, such as continuous phase modulation (CPM) provide gain over non-constant formats, such as QPSK. Consideration is made to scaling to 100 Gb/s and beyond in practical implementations.

Polarization multiplexing is an integral technique for generating spectrally efficient 100 Gb/s and higher optical links. Post coherent detection DSP-based polarization demultiplexing of QPSK links is commonly performed after timing recovery. We propose and demonstrate a method of asynchronous blind source separation using the constant modulus algorithm (CMA) on the asynchronously sampled signal to initially separate energy from arbitrarily aligned polarization states. This method lends well to implementation as it allows for an open-loop sampling frequency for analog-to-digital conversion at less than twice the symbol rate. We show that the performance of subsequent receiver functions is enhanced by the initial pol demux operation. CMA singularity behavior is avoided through tap settling constraints. The method is applicable to QPSK transmissions and many other modulation formats as well, including general QAM signals, offset-QPSK, and CPM, or a combination thereof. We present the architecture and its performance under several different formats and link conditions. Comparisons of complexity and performance are drawn between the proposed architecture and conventional receivers.

For the first time native IP data are carried end-to-end by 100 GE router interfaces and a 100 G optical transport system over 1520-km field deployed fiber. This is accomplished with multi-suppliers' 112-Gb/s single carrier real time coherent DP-QPSK DWDM transponder, 100 GE router cards, and 100 G CFP interfaces.

The use of trellis-coded modulation (TCM) in combination with an outer block code is considered for next-generation 100-Gb/s optical transmission systems. Two block codes are employed as an outer code: a 16 times interleaved byte-oriented (255,239) Reed Solomon (RS) code and a code consisting of two interleaved extended three-error correcting Bose Chaudhuri Hocquenghem (BCH) (1020,988) codes. Simulations show that soft-decision decoding of a selected TCM inner code in combination with hard-decision decoding of the outer RS code achieves a net coding gain (NCG) of 8.42 dB at a bit-error rate of 10-13. When the concatenated code based on the two interleaved BCH codes is used as the outer code, the NCG is 9.7 dB. The impact of quantization on the performance of the concatenated TCM scheme with the two interleaved BCH outer codes is evaluated, and it is shown that 4-bit quantization is sufficient to approach the "infinite precision" performance to within 0.15 dB.

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.

We demonstrate Offset-QPSK transmitter and receiver architectures for 112 Gb/s coherent optical networks, highlighting similarities and differences to QPSK implementations. Experimentally we demonstrate that O-QPSK exhibits an enhanced immunity to nonlinearities when transmitted over TrueWave ® fiber links.

A brief review of Verizon's 100 G field trials leading to commercial deployment and considerations for a new network infrastructure for bit rates up to 1 Tb/s are presented.

Constant envelope formats including CPM may reduce the impact of nonlinear impairments arising from intensity variations and the associated nonlinear phase noise. We quantify the advantages of CPM versus QPSK and identify possible deployment opportunities.

Successful transmission of live (real time) video traffic is demonstrated using a prototype 100 Gb-s single-polarization differential quadrature phase shift keying (DQPSK) transmitter and receiver over an in-service 504 km link of the LambdaXtreme® optical transport platform. Teaming with Verizon Business, we demonstrate the feasibility of upgrading an existing, live traffic bearing network to 100 Gb-s per wavelength without any changes to the current hardware or software. The 107 Gb-s signal is added at a reconfigurable optical add-drop multiplexer (ROADM) at a network node in Tampa, Florida, and dropped at a ROADM in Miami, Florida, where both live video and pseudorandom test sequences are received. In addition, we discuss the steps leading up to this field trial that included several important precursor laboratory experiments. We detail the generation, detection, coding, and long-haul transmission of single-polarization DQPSK at a line rate of 53.5Gbaud to support a net information bit rate of 100 Gb-s. © 2010 Alcatel-Lucent.

Networks are transitioning from TDM to packet transport optimized architectures. Packet networks are based on technologies traditionally lacking OAM tools. We will present the OAM tools being developed and their application to the transport layers.

Advances in optical technology now allow practical reconfigurable wavelength networks to be constructed. These networks use wavelength-switching components to dynamically route wavelengths, and provide a level of flexibility and scalability previously not possible. Other components such as low-noise optical amplifiers, electronic dispersion compensators, and advanced modulation techniques simplify system operation, increase capacity, and extend reach. From an application perspective, the architecture of optical transport networks is evolving based on the requirement to support a higher bandwidth access infrastructure. The network architecture also needs to provide the flexibility to incrementally expand on the basis of customer demand and to provide key features such as optical broadcast to lower the cost of video services. The development of new architectures for optical transport networks and how these networks are influenced by critical system parameters and emerging component technologies is reviewed

We described the error-control problems associated with supporting ATM transmission of multimedia services on line of sight (LOS) radio circuits. The major problems to address are associated with poor circuit quality and limited transmission bandwidths. Poor circuit quality is manifested by low received SNRs and high delivered BERs and can be improved by judicious application of error-control coding. The desire to support as many ATM users as possible and the constraint of limited bandwidth favor the use of high-rate coding techniques. To provide an acceptable QoS, however, the selected coding technique must be effective for all realistic channel conditions, including AWGN and slow Rician fading. It was shown that binary BCH codes can be used to provide a highly effective error-control technique for ATM transmission on LOS circuits. The wide selection of block lengths, rate, and error correction power allows solutions to be tailored to the wireless ATM application. It was shown that the best designs result when a powerful binary BCH code is used to protect the header and a somewhat less powerful code is used to protect the payload. The effects of residual uncorrected error events can then be addressed with an appropriate end-to-end error-control technique, or, in the case of MPEG video, with error concealment algorithms. It was also shown that Reed Solomon codes with erasure filling can provide an effective, high-rate, end-to-end coding scheme to protect against cell loss due to congestion in ATM networks and decoding failure events associated with the link codes.