Networks

We propose an optical 3R regenerator that incorporates a clock enhancement stage based on a semiconductor optical amplifier (SOA)-based Mach-Zehnder interferometer and a 10-GHz all-optical clock recovery module employing a Fabry-Perot filter and an SOA. The experiments assess the optical 3R regeneration technique using a fiber recirculation loop containing 125-km dispersion uncompensated large effective area fiber with a total chromatic dispersion of 531.25 ps/nm. The optical 3R regeneration achieves error-free 125 000-km dispersion uncompensated return-to-zero transmission at 10 Gb/s over 1000 optical 3R stages. The bit-error-rate (BER) measurements show that there is only 1.2-dB power penalty at 10 9 BER between 125 000-km (Lap 1000) uncompensated transmission and back-to-back using pseudorandom bit sequence 2 23 1. Index Terms-All-optical clock recovery, dispersion uncompensated transmission, Fabry-Pérot filter (FPF), optical regeneration, semiconductor optical amplifier-based Mach-Zehnder interferometer (SOA-MZI), synchronous modulation, wavelength conversion.

Using asymmetric narrow-band optical filtering to improve the response and reshape the optical spectrum of a commercial directly modulated distributed feedback laser, we demonstrate 40-Gb/s error-free transmission over 25-km negative dispersion fiber without dispersion compensation.

We experimentally demonstrate a polarization-mode dispersion (PMD) monitoring technique that is insensitive to chromatic dispersion (CD) utilizing a polarizer and a low-speed detector for an 80-Gb/s polarization-multiplexed return-to-zero differential phase-shift-keying (pol-muxed RZ-DPSK) data channel. Measured RF power increment of 16.2 dB, which is insensitive to 0 approximately 100 ps/nm CD, is measured in the presence of the increasing differential group delay (DGD) from 0 to 12 ps. High-speed components are not required for monitoring the PMD on the pol-muxed data channel, which means that the proposed technique is potentially applicable to the higher speed pol-muxed data channels.

We introduce a probabilistic framework, based on service risk mitigation and disruption management, for the problem of capacity protection in optical networks. This is in contrast to the established deterministic approach of designing the protection network to guarantee no service disruption for up to M failures. We present the novel problem formulation and establish a framework for optimal network design in this extended abstract, while leaving the detailed optimization results and algorithms for the full paper [1].

We demonstrate an alternative differential quadrature phase-shift keying (DQPSK) receiver offering reduced complexity through sharing of hardware in the I=Q demodulation paths. Demodulation of 43-Gb/s return-to-zero DQPSK is demonstrated without penalty relative to a traditional DQPSK receiver. Rate tuning is demonstrated using a tunable birefringent element.

Multibit delay demodulation of differential-phase shift-keying (DPSK) is finding applications in polarization interleaved modulation, optical time-domain multiplexing (OTDM), and multisymbol DPSK demodulation. Little attention has been paid to the degradation in tolerance and power penalty associated with multibit delay demodulation. We assess experimentally, numerically, and analytically the power penalties and tolerances associated with multibit delay DPSK demodulation. Numerical and analytical results show that the power penalty scales by a small factor of 0.2-0.35 dB per integer bit delay due to laser linewidth (LW) while experimental back-to-back results show a significant 1.2 dB per integer bit delay due to frequency offset penalty of longer bit delays. Frequency offset tolerance scales as 1/bit-delay and the delay-mismatch tolerance decreases by 20% for delays longer than 1 bit. A simple analytic model accounts for the combined effect of LW, frequency offset, and amplified spontaneous emission.

This letter demonstrates optical 3R regeneration in 10-Gb/s nonreturn-to-zero field transmission. The 3R regenerator utilizes semiconductor-optical-amplifier-based Mach-Zehnder interferometer wavelength converters, a synchronous modulator, and a Fabry-Pérot filter to realize optical 3R regeneration including all-optical clock recovery. The cascadablity of the 3R regenerator is investigated in recirculating loop transmission experiments with various regeneration spacings up to 462 km (corresponding to an input optical signal-to-noise ratio (OSNR) of 22 dB). Transmission with the 3R regenerator shows significant performance improvement over that without 3R regeneration. A 66-km-spaced 3R regeneration with a 33-dB input OSNR achieves 1000-hop cascaded error-free transmission (66 000 km in distance) with no hop-to-hop power penalties. A 264-km-spaced 3R regeneration with a 25-dB input OSNR also achieves 100-hop cascaded transmission (26 400 km in distance) with a bit-error-rate error floor at 1 10 8 .

We experimentally demonstrate a technique for monitoring the time misalignment of in-phase/quadrature (I/Q) data streams and pulse carver/data in a 20-Gb/s return-to-zero differential quadrature phase-shift-keying (RZ-DQPSK) transmitter. By measuring the radio-frequency clock-tone power at 10 GHz and low frequency power at 600 MHz, a monitoring power dynamic range of 18 dB is obtained for I/Q data misalignment and 6 dB is shown for carver/data misalignment. With the monitor information, a simple feedback loop is proposed to automatically align the RZ-DQPSK transmitter.

This letter demonstrates the efficacy of an optical arbitrary waveform generation (OAWG) transmitter in generating high-bandwidth, single-channel optical waveforms with precompensation overcoming chromatic dispersion. Specifically, 20-bit, 200-Gb/s differential phase-shift keying and 40-bit, 400-Gb/s quadrature phase-shift keying packets are precompensated for the 1675.16 ps/nm of dispersion and 4.833 ps nm 2 of dispersion slope present in 100 km of single-mode fiber, and successfully recovered after transmission. The repetitive waveform packets were generated using static OAWG methodology, with a pair of silica arrayed-waveguide gratings through line-by-line pulse shaping.

We propose and demonstrate an adaptive quality of transmission (QoT) restoration scheme combining the methods of lightpath rerouting and modulation-format switching to overcome real-time impairments in elastic optical networks. A hybrid objective algorithm is designed to minimize the spectral consumption and the interference that the rerouting imposes on the other parts of the network. Simulation results show the algorithm achieved more than 50% reduction in blocking probability and 75% decrease in the spectral consumption on the bypass links compared with the rerouting-only method. Testbed experiments demonstrated successful real-time QoT restoration in the presence of time-varying optical signal-to-noise ratio impairment for two simultaneously impaired 100 and 200 Gb/s quaternary phase-shift keying superchannels.

This paper proposes and demonstrates optical 3R regeneration techniques for high-performance and scalable 10-Gb/s transmission systems. The 3R structures rely on monolithically integrated all-active semiconductor optical amplifier-based Mach-Zehnder interferometers (SOA-MZIs) for signal reshaping and optical narrowband filtering using a Fabry-Pérot filter (FPF) for all-optical clock recovery. The experimental results indicate very stable operation and superior cascadability of the proposed optical 3R structure, allowing error-free and low-penalty 10-Gb/s [pseudorandom bit sequence (PRBS) 2 23 -1] return-to-zero (RZ) transmission through a record distance of 1 250 000 km using 10 000 optical 3R stages. Clock-enhancement techniques using a SOA-MZI are then proposed to accommodate the clock performance degradations that arise from dispersion uncompensated transmission. Leveraging such clock-enhancement techniques, we experimentally demonstrate error-free 125 000-km RZ dispersion uncompensated transmission at 10 Gb/s (PRBS 2 23 -1) using 1000 stages of optical 3R regenerators spaced by 125-km largeeffective-area fiber spans. To evaluate the proposed optical 3R structures in a relatively realistic environment and to investigate the tradeoff between the cascadability and the spacing of the optical 3R, a fiber recirculation loop is set up with 264-and 462-km deployed fiber. The field-trial experiment achieves error-free 10-Gb/s RZ transmission using PRBS 2 23 -1 through 264 000-km deployed fiber across 1000 stages of optical 3R regenerators spaced by 264-km spans.

This paper proposes and demonstrates a simulation model to systematically investigate jitter accumulations in cascaded all-optical 2R regenerators. The simulation results indicate that when the pattern dependence from the memory effect is minimized, the jitter accumulation depends critically on the degree of the regenerative nonlinearity. Studies of tradeoffs between the jitter from bandwidth limitation and the signal-to-noise-ratio degradation help identify the optimized regenerator bandwidth for various degrees of regenerative nonlinearity. The simulation then considers the pattern dependence from the memory effect and finds that it can severely degrade the cascadability of an optical 2R regenerator and can make it worse than that of a linear optical amplifier (optical 1R). The simulation results show good matches to the experimental results of an optical 2R regenerator based on a semiconductor optical amplifier based Mach-Zehnder interferometer. To overcome the jitter accumulation associated with the optical 2R regeneration, we experimentally demonstrate an optical 3R regenerator for optical nonreturn-to-zero signals with all-optical clock recovery. The experiments achieve more than 1000-hop cascadability for pseudorandom binary sequence 2 31 1 inputs with a 100-km recirculation loop using lab fiber. Field trial experiments then demonstrate a more than 1000-hop cascadability for a 3R spacing of 66 km and a 100-hop cascadability for a 3R spacing of 264 km.

We demonstrate an all-optical clock-and-data recovery technology for 10-Gb/s NRZ-DPSK signals. With a relatively simple configuration, the clock-recovery scheme achieves less than 1.5-ps RMS jitter for signals after fiber transmission. The pattern-dependence of data-recovery is within 0.5-dB at BER 10 -9 .

This paper demonstrates optical 3R regeneration distance is demonstrated utilizing a reconfigurable for a 10 Gb/s nonreturn-to-zero (NRZ) data format. recirculating loop transmission setup that facilitates Semiconductor optical amplifier based Mach-Zehnder transmission with variable 3R regeneration spacings. interferometer (SOA-MZI) wavelength converters, synchronous modulator, and Fabry-Perot filter (FPF) are used for 3R regenearation including all-optical clock 2. Experimental Setup recovery. Recirculating loop transmission experiments compare transmission performances with different 3R 2.1 Reconfigurable Recirculating Transmission Setup regenation spacings. Transmission with the 3R regenerator shows significant performance improvement over that Figure 1 shows the setup for recirculating loop transmission without 3R regeneration in terms of eye diagram, Q-factor, to evaluate transmission performance with cascaded 3R and transmission distance. Q-factors around 20 dB are regenerators. The transmitter generates 10 Gb/s NRZ obtained up to a transmission distance of 5000 km when the signal. The 100-km dispersion-compensated transmission 3R regeneration spacing is 100 or 500 km. line consists of two sets of 50-km LEAF fibers followed by a two-stage erbium-doped fiber amplifier (EDFA) and a dispersion compensating fiber (DCF). To reduce optical Keywords: All-optical clock recovery, Fabry-Perot filter, signal-to-noise ratio (OSNR) degradation while maintaining nonreturn-to-zero format, optical regeneration, the linear optical transmission regime, the input power semiconductor optical amplifier based Mach-Zehnder levels to the LEAF and DCF fibers are set moderately high interferometer at 5 dBm and -3 dBm, respectively. The measured OSNR and the estimated residual dispersion at the 3R regenerator input are 37.7dB (0.1 nm bandwidth) and 22 ps/nm, 1. Introduction respectively. Three acoustic optical modulator (AOM)

We demonstrate field trial experiments to evaluate a 10-Gb/s optical 3R regenerator using fiber recirculation loops built with 264-km and 462-km SSMF fiber in field. Error-free transmission over 264,000-km with 1,000 optical 3R regeneration stages has been achieved. Experimental results indicate only 1.5-dB power penalty at BER 10 -9 after 264,000-km.

We demonstrate a proof-of-principle transmitter for flexible-bandwidth network with parallel synthesis and a wavelength-selective switch. Impairment-aware spectrum allocation is used to maintain data rates in spite of varying signal-to-noise ratio.

This paper experimentally demonstrates flexible-bandwidth networking by splitting a 500-GHz waveform generated by optical arbitrary waveform generation into its two tributary spectral slices using a liquid-crystal spatial light phase modulator as a wavelength selective switch.