Masaki Funabashi

10 000-hop cascaded in-line all-optical 3R regeneration to achieve 1 250 000-km 10-Gb/s transmission

We demonstrate 1 250 000-km 10-Gb/s return-to-zero transmission over 10 000 stages of in-line all-optical reamplification, reshaping, and retiming (3R) regeneration spaced every 125 km. The all-optical 3R regenerator incorporates a 10-GHz all-optical clock recovery module including a Fabry-Pe/spl acute/rot filter and a semiconductor optical amplifier in a cascaded configuration for fast and stable response. Bit-error-rate (BER) performance measurements show less than 0.7-dB power penalty at the BER of 10/sup -9/ between 1 250 000- (Lap 10 000) and 125-km (Lap 1) transmission using pseudorandom bit sequence 2/sup 23/-1.

High-Performance Optical 3R Regeneration for Scalable Fiber Transmission System Applications

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-Peacuterot 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) 223-1 ] 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 223-1) using 1000 stages of optical 3R regenerators spaced by 125-km large-effective-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 223-1 through 264 000-km deployed fiber across 1000 stages of optical 3R regenerators spaced by 264-km spans

Jitter and Amplitude Noise Accumulations in Cascaded All-Optical Regenerators

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 231-1 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.

1000 cascaded stages of optical 3R regeneration with SOA-MZI-based clock enhancement to achieve 10-gb/s 125 000-km dispersion uncompensated transmission

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 223-1

All-Optical Label Swapping, Clock Recovery, and 3R Regeneration in 101-Hop Cascaded Optical-Label Switching Router Networks

This paper experimentally demonstrates the cascaded operation of an optical-label switching router for up to 101 hops, with optical label swapping, optical clock recovery, and 3R regeneration (re-amplification, reshaping, and retiming) at each hop. The optical label swapping utilizes all-optical payload/label separation and label rewriting with subcarrier label. An interferometer wavelength converter enables the reshaping function, while the synchronous modulation driven by the optically recovered packet clock performs the retiming function. The optical label swapping and 3R regeneration enable the packets to traverse a large number of hops while maintaining the signal quality to support the scalability of the optical-label switching network

Cascadability of Optical 3R Regeneration for NRZ Format Investigated in Recirculating Loop Transmission Over Field Fibers

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-Perot filter to realize optical 3R regeneration including all-optical clock recovery. The cascadability 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 400km in distance) with a bit-error-rate error floor at ~1times10-8

Optical Clock Recovery and 3R Regeneration for 10-Gb/s NRZ Signal to Achieve 10 000-hop Cascadability and 1 000 000-km Transmission

This letter experimentally demonstrates all-optical clock recovery and optical 3R regeneration for a 10-Gb/s nonreturn-to-zero (NRZ) format. The 3R regenerator has achieved 10 000-hop cascadability and 1 000 000-km transmission for a pseudorandom bit sequence (PRBS) of 27-1. A semiconductor-optical-amplifier-based Mach-Zehnder interferometer (SOA-MZI) as an NRZ to pseudoreturn-to-zero converter and a Fabry-Perot filter perform the all-optical clock recovery from an NRZ signal. A pair of SOA-MZIs combined with a synchronous modulator provides the 2R regeneration and retiming functions. The cascadability of the 3R regenerator is investigated in a recirculating loop transmission experiment by eye diagram, bit-error rate, and Q-factor measurements. Transmission with the 3R regenerator shows significant performance improvement over that without 3R regeneration. A 100-hop cascadability is also demonstrated for PRBS 231-1, enabling 10 000-km error-free transmission with a low power penalty of 1.2 dB

101-hop cascaded operation of an optical-label switching router with all-optical clock recovery and 3R regeneration

This paper experimentally demonstrates the cascaded operation of an optical-label switching router for up to 101hops with 3R regeneration (reamplification, reshaping, and retiming). A semiconductor optical amplifier-based Mach-Zehnder interferometer wavelength converter performs the reshaping. A Fabry-Peacuterot filter all-optically recovers the clock from the incoming packets. Synchronous modulation by a LiNbO3 modulator using the recovered clock performs the retiming. The 3R regeneration maintains good signal quality in the cascaded operation, which is important for scalable optical networking

Nanosecond guard time packet-by-packet burst-mode optical 3R regeneration in an optical-label switching router

This letter discusses an experimental demonstration of 10-Gb/s packet-by-packet burst-mode optical 3R regeneration in an optical-label switching router. A monolithically integrated Mach-Zehnder interferometer with semiconductor optical amplifiers provides the all-optical 2R regeneration. Synchronous modulation with the use of Fabry-Pe/spl acute/rot filter-based clock recovery performs the burst-mode retiming function necessary for 3R regeneration. The clock recovery works successfully despite a clock phase discontinuity between adjacent packets. The optical 3R regenerator shows bit-error rates below 1/spl times/10/sup -10/ and sensitivity variations less than 1.5 dB over a wide range of guard times from 3 to 1000 ns.

Error-free 31-hop cascaded operation of an optical packet switching router with all-optical 3R regeneration

This paper demonstrates 31-hop cascaded operation of an optical-label switching router. The all-optical 3R regeneration enables error-free 31-hop cascaded packet switching with no additional penalty beyond 3 hops up to 31 hops.