A 10-Gb/s 1024-Way-Split 100-km Long-Reach Optical-Access Network

Optical-access networks have been developed to remove the access-network bandwidth bottleneck. However, the current solutions do not adequately address the network economics to provide a truly cost-effective solution. Long-reach optical-access networks introduce a cost-effective solution by connecting the customer directly to the core network, bypassing the metro network, and, hence, removing significant cost. This paper charts the design and development of a 1024-way-split 100-km 10-Gb/s symmetrical network, which experimentally proves the feasibility of long-reach optical-access networks for both the upstream and downstream transmission.     

Rayleigh Backscattering Noise-Eliminated 115-km Long-Reach Bidirectional Centralized WDM-PON With 10-Gb/s DPSK Downstream and Remodulated 2.5-Gb/s OCS-SCM Upstream Signal

We propose a novel scheme of Rayleigh backscattering noise-eliminated, long-reach, single-fiber, full-duplex, centralized wavelength-division multiplexed passive optical network with differential quadrature phase-shift keying (DPSK) downstream and remodulated upstream using an optical carrier-suppressed subcarrier-modulation (OCS-SCM) technique and optical interleaver. The error-free transmissions of 10-Gb/s downstream and 2.5-Gb/s upstream signals are experimentally demonstrated over 115-km single-fiber bidirectional SMF-28 with less than 0.5 and 1.9 dB power penalties, respectively.      

Burst-Mode Electronic Equalization for 10-Gb/s Passive Optical Networks

Using computer simulations, it is shown how burst-mode electronic equalization in the optical line termination of a passive optical network (PON) allows 10 Gb/s in the upstream direction with directly modulated distributed-feedback lasers. This allows achieving 10 Gb/s using cost-effective components at the optical network unit. Fast convergence of the equalizer coefficients is achieved during the preamble of each burst using the recursive least squares algorithm instead of the least mean squares algorithm. With a nine-tap feed-forward equalizer, two-tap decision feedback equalizer, a physical reach of 38 km and a splitting factor of 32 can be achieved in the 1.5-$mu$m window, exceeding requirements for deployed PONs.      

Coherent Optical 25.8-Gb/s OFDM Transmission Over 4160-km SSMF

We discuss coherent optical orthogonal frequency division multiplexing (CO-OFDM) as a suitable modulation technique for long-haul transmission systems. Several design and implementation aspects of a CO-OFDM system are reviewed, but we especially focus on phase noise compensation. As conventional CO-OFDM transmission systems are very sensitive to laser phase noise a novel method to compensate for phase noise is introduced. With the help of this phase noise compensation method we show continuously detectable OFDM transmission at 25.8 Gb/s data rate (20 Gb/s after coding) over 4160-km SSMF without dispersion compensation.     

Dispersion-Compensation Schemes for 160-Gb/s 1200-km Transmission by Optical Phase Conjugation

Appropriate dispersion management possesses the superiority to relax the limitation of nonlinearities in high-speed transmission systems employing optical phase conjugation (OPC). In this paper, several dispersion-compensation schemes have been analytically and numerically investigated in a 160-Gb/s OPC system. A comprehensive performance comparison of these schemes over 1200-km transmissions has been carried out to present a reference for future OPC system designs. The scheme with a gradient dispersion map is recommended, particularly for G.655 fiber with a relatively low local dispersion.     

10-Gb/s Operation of RSOA for WDM PON

We report on the 10-Gb/s operation of the reflective semiconductor optical amplifier (RSOA) for the next-generation wavelength-division-multiplexed passive optical network (WDM PON). The bandwidth of the RSOA used in this experiment is merely 2.2 GHz. Nevertheless, a clear eye opening is obtained at 10 Gb/s by using the electronic equalizer processed offline. We investigate the impacts of the network's operating conditions (such as the injection power to the RSOA and the fiber length) on the performances of these equalizers. The results show that the RSOA-based WDM PON is operable at 10 Gb/s and the maximum reach can be extended to ${>}$ 20 km with the help of the forward error correction codes.      

Routing of 40-Gb/s Streams in Wavelength-Routed Heterogeneous Optical Networks

In this paper, we address the design and management issues in routing a mixture of OC-192 and OC-768 streams in wavelength-routed optical networks. We assume that fiber links in the network are heterogeneous with respect to their transmission capability (i.e., links are designed to handle a given maximum bit-rate imposed by regenerator spacing).We investigate the issues of routing connection demands of various bit-rate requirements in such heterogeneous networks. In this environment, we introduce the routing of multirate traffic (RMT) problem. The RMT problem is informally defined as the process of finding the best routing which maximizes the total bandwidth carried in the network, for a set of sessions, within a given TDM equipment budget. We propose a two-phase optimization scheme (two-phase RMT). This scheme first obtains a basis solution used in routing 40-Gb/s traffic only on OC-768 capable links without the use of TDM equipment. In the second phase, an iterative routing, rerouting, and resource allocation step is used to optimize the total bandwidth carried in the network, while allowing 40-Gb/s traffic to be routed on OC-768 incapable links by the proper installation of TDM multiplexors and demultiplexers at some strategic locations in the network. Numerical results reveal the following:. 1) the two-phase RMT optimization algorithm provides substantial savings in terms of both the total TDM equipment installed and number of wavelengths used; 2) noticeable enhancements of the bandwidth utilization and the TDM budget are observed when the route-optimization takes into account the transmission quality of the links; and 3) the use of intermediate TDM multiplexing/demultiplexing functions provides substantial savings, in terms of the total number of channels, over the source-splitting scheme.     

Applications of 40-Gb/s Chirp-Managed Laser in Access and Metro Networks

We investigate 40-Gb/s cost-efficient transmitter for access and metro networks. This 40-Gb/s transmitter comprises a standard directly modulated distributed-feedback (DFB) laser and a subsequent optical filter. Large dispersion tolerance of this transmitter is realized by chirp control through the phase correlation between adjacent bits for the destructive interference in order to erase the power of “0” bits while enhancing the extinction ratio. The chirp model of the DFB laser and the optimum parameters of the optical filter have been numerically analyzed. The chirp-managed 42.8-Gb/s transmission over 20-km standard single mode fiber (SSMF or SMF-28) without dispersion compensation and a centralized lightwave WDM-PON system are experimentally demonstrated. We have also realized the transmission over 100-m graded index plastic optical fiber (GI-POF). Moreover, the application in the metro network over 240-km SSMF or SMF-28 has also been investigated in this paper.      

111-Gb/s Transmission Over 1040-km Field-Deployed Fiber With 10G/40G Neighbors

We demonstrate transmission of a 111-Gb/s coherent polarization-multiplexed return-to-zero differential quadrature phase-shift keying signal over 1040-km field-deployed fiber together with different types of neighboring channels, and with a cascade of 50-GHz reconfigerable optical add-drop multiplexers. Our transmission experiment proves the feasibility of transmitting a 111-Gb/s phase-modulated channel with 10 times 10.7-Gb/s on-off keying neighboring channels on a 50-GHz grid, despite the presence of strong cross-phase modulation.     

Wavelength Remodulation Using DPSK Down-and-Upstream With High Extinction Ratio for 10-Gb/s DWDM-Passive Optical Networks

We propose and demonstrate a novel wavelength remodulation scheme using differential phase-shift keying (DPSK) modulation format in both downstream and upstream signals for ldquocolorlessrdquo dense wavelength-division-multiplexed (DWDM) passive optical networks (PONs). The scheme enables high extinction ratio in both downstream and upstream remodulated signals. Error-free operation was achieved in a 20-km-reach 10-Gb/s DWDM-PON without dispersion compensation. Timing misalignment tolerance between downstream and upstream remodulated signals and maximum launched optical power for the proposed scheme are studied. Comparison with other wavelength remodulation schemes for DWDM-PONs is also performed, showing the proposed scheme can be a potential candidate for next-generation wavelength reuse DWDM-PONs.     

Statistics of Electrical Dispersion Compensator Penalties of 10-Gb/s Multimode Fiber Links With Offset Connectors

In this letter, we investigate the penalty after a 10-Gb/s Ethernet signal is detected and processed. We study the statistics of ideal electrical dispersion-compensation (EDC) performance, measured by the penalty of an ideal decision feedback equalizer (PIE-D), of 300-m multimode fiber links to determine the theoretically best possible EDC performance. We calculate the channel responses using two methods: the individual-mode method and the average-mode method. We find a strong dependence of the PIE-D value on the channel model that is used, especially when there is a connector with a large offset in the link. In system design, one should choose a suitable channel model, taking into account the length of the fiber, the magnitude of offset, and the percentage of coverage     

Precompensation for Narrow Optical Filtering of 10-Gb/s Intensity Modulated Signals

Signals in spectrally efficient optical networks can be distorted by the narrowing of the overall bandwidth that occurs when optical add-drop multiplexers are concatenated. In this letter, it is demonstrated that the performance implications of this bandwidth narrowing can be mitigated by precompensation using arbitrary optical waveform generation. The synthesis of the required voltage waveforms for a dual-drive Mach-Zehnder modulator reduces the penalty in receiver sensitivity due to narrow optical filtering from 6.5 to 1.9 dB. Simultaneous precompensation for fiber dispersion is also demonstrated.     

A 690-mW 1-Gb/s 1024-b, rate-1/2 low-density parity-check codedecoder

A 1024-b, rate-1/2, soft decision low-density parity-check (LDPC) code decoder has been implemented that matches the coding gain of equivalent turbo codes. The decoder features a parallel architecture that supports a maximum throughput of 1 Gb/s while performing 64 decoder iterations. The parallel architecture enables rapid convergence in the decoding algorithm to be translated into low decoder switching activity resulting in a power dissipation of only 690 mW from a 1.5-V supply     

Optical Burst Switching Router With 40-,10-Gb/s Bit-Rate Transparent Contention Resolution

We report a bit-rate transparent optical burst switching (OBS) router prototype using a fast 5 times 5 PLZT [(Pb,La)(Zr,Ti)O₃ ] optical matrix switch. Dynamic switching in a two-wavelength, 2 times 2 OBS switch is demonstrated. Contention resolution using a tunable Mach-Zehnder interferometer wavelength converter for both 40- and 10-Gb/s bursts is demonstrated for the first time. Error-free operation was achieved for both bit rates under the same settings, as required in autonomous networks     

18 Gchips/s Electronic CDMA for Low-Cost Optical Access Networks

This paper reports, for the first time, the coding and decoding of code-division multiple-access (CDMA) signals for use in optical access networks using electronic transversal filters at a chip rate of 18 Gchips/s, a ninefold improvement over previous demonstrations. We demonstrate a 2-user ECDMA system. The use of 7-chip transversal filters gives a potential for 7 users, where each user has a data rate of 1.25 Gb/s. This is comparable to typical all-optical CDMA systems but with potentially lower cost, power consumption and complexity. Error-free transmission of a 1.25 Gb/s electronic CDMA user signal, with and without a single interferer, over 10 km of single-mode fiber is reported for the first time.      

400-ns Continuously Tunable Delay of 10-Gb/s Intensity Modulated Optical Signal

A continuously tunable optical delay line based on a two-pump parametric process in a highly nonlinear fiber providing 400.5-ns range for a 10-Gb/s optical signal is reported. This record 4005-bit delay used fixed dispersion elements, compatible with requirements for fast delay reconfiguration. The large delay range was made possible by partial dispersion slope cancelation.      

40-Gb/s Time-Division-Multiplexed Passive Optical Networks Using Downstream OOK and Upstream OFDM Modulations

In this investigation, we first propose and investigate a 40-Gb/s time-division-multiplexed passive optical network (TDM-PON) using four wavelength-multiplexed signals in both downstream and upstream traffic. Here, each downstream signal uses 10-Gb/s on–off keying (OOK) format encoded by a Mach–Zehnder modulator (MZM) in 1.5-$mu{hbox {m}}$ band. And each upstream channel utilizes the highly spectral efficient 10-Gb/s orthogonal frequency-division-multiplexing quadrature amplitude modulation (OFDM-QAM) generated by directly modulating a 1.3-$mu{hbox {m}}$ laser. Based on the proposed scheme, 40-Gb/s data traffic in a TDM-PON can be obtained easily by using four wavelength-multiplexed channels. In addition, the performance of the proposed PON architecture has also been discussed.      

Single-Fiber Access/Metro WDM Ring Architecture for Asymmetric Traffic Applications in Next Generation Networks

The next generation network (NGN) and the speed-up of access lines will sharply increase the demand for one-way applications such as internet protocol television (IP TV) and video on demand (VOD). One-way applications make the downlink bandwidth much larger than the uplink bandwidth. Asymmetric traffic is best supported by using different numbers of wavelengths in the uplink and downlink, which presumes the use of a wavelength division multiplexing (WDM) network. Unfortunately, the existing 2- or 4-fiber ring network architecture is symmetric, and so it cannot efficiently accommodate asymmetric paths. This paper proposes a novel 1-fiber WDM protection ring that offers a cost-effective optical network architecture for asymmetric traffic as well as symmetric traffic. It also proposes a new 1:1 protection switching scheme and automatic protection switching (APS) control protocol that can reduce capital expenditures for optical-electro-optical termination cards and provide nonrevertive protection switching with extra traffic and APS with end-to-end supervision including optical switching fabrics. Moreover, this paper shows that the proposed wavelength switching scheme offers much better network survivability after multiple wavelength failures than the existing bidirectional switching scheme can offer.     

10-Gb/s Wavelength Transparent Optically Controlled Buffer Using Photonic-Crystal-Fiber-Based Nonlinear Optical Loop Mirror

We have proposed and experimentally demonstrated a 10-Gb/s optically controlled buffer using a photonic-crystal-fiber (PCF)-based nonlinear optical loop mirror for all-optical packet-switched networks. The 10-Gb/s data can be stored in the buffer up to a period of 2.5 mus. By using the cross-phase modulation property between the control signal and the data signal inside the PCF, the total length of the fiber used in the buffer can be shortened to 30.9 m. The stored data packets are retrieved after they are stored in the memory for 2,4,..., and 12 round-trips. Independent bit-error-rate (BER) measurements have been carried out. The maximum power penalty is 3.3 dB at 1550 nm. The proposed buffer is wavelength transparent. For data packets stored in the C-band, the maximum power penalty after the data are stored in the memory for 12 round-trips is 3.5 dB at the BER of 10^-9     

20-Gb/s PolDM Duobinary Transmission Over 350-km SSMF Supported by a Polarization Stabilizer and an Optical Dispersion Compensator

A 20-Gb/s transmission over 350-km standard single-mode fiber exploiting duobinary dispersion robustness and polarization-division multiplexing has been demonstrated. The system performance is evaluated employing an automatic endless polarization stabilizer and a suitably designed transmitter-side optical dispersion compensator.