All-optical 2R Regeneration Research Articles

Self-phase modulation-based integrated optical regeneration in chalcogenide waveguides

We demonstrate integrated all-optical 2R regenerators based on Kerr optical nonlinearities (subpicosecond response) in chalcogenide glass waveguides with integrated Bragg grating filters. By combining a low loss As/sub 2/S/sub 3/ rib waveguide with an in-waveguide photo-written Bragg grating filter, we realize an integrated all-optical 2R signal regenerator with the potential to process bit rates in excess of 1 Tb/s. The device operates using a combination of self phase modulation induced spectral broadening followed by a linear filter offset from the input center wavelength. A nonlinear power transfer curve is demonstrated using 1.4 ps pulses, sufficient for suppressing noise in an amplified transmission link. We investigate the role of dispersion on the device transfer characteristics, and discuss future avenues to realizing a device capable of operation at subwatt peak power levels.

Optical 40-gb/s 3R regenerator with a combination of the SPM and XAM effects for all-optical networks

An all-optical 3R regenerator with a combination of self-phase modulation (SPM) and cross-absorption modulation (XAM) effects is proposed and investigated. Principle performances of the proposed all-optical 3R regenerator were experimentally investigated at a signal bit rate of 40 Gb/s. The all-optical 3R regenerator, which is located at the midpoint of a 1080-km transmission line, successfully provided an approximately 3-dB improvement of the Q-factor both just after regeneration and after totally 1080-km transmission. The chromatic dispersion tolerance of the proposed 3R regenerator was also investigated and successfully enhanced to about twice as wide by introducing a predistortion block configuration including a highly nonlinear fiber (HNLF). It was confirmed that the proposed all-optical 3R regenerator can become one of the strong candidates for the actual deployment of the all-optical network

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.

All-optical 2R regeneration based on a compact self-seeded fabry-Pe/spl acute/rot laser diode with an embedded fiber Bragg grating

A cost-effective method, based on the injection-locking technique of a compact self-seeded Fabry-Peacuterot laser diode with a 10-mm-long embedded fiber Bragg grating cavity, is proposed and experimentally compared with the two-mode injection-locked scheme for all-optical 2R regeneration at 10 Gb/s. Placing the presented all-optical 2R regenerator after a 50-km fiber significantly improves the transmission performance of a signal over 50- and 100-km fiber links. The power penalties at BER=10-9 are similar to those of the two-mode injection-locked scheme

Efficient all-optical 2R regeneration using self-phase modulation in bidirectional fiber configuration

An efficient wavelength-conversion-free all-optical 2R regenerator is proposed. The regeneration is based on power-dependent spectrum broadening in normal-dispersion fiber and subsequent off-centered filtering. Twofold regeneration is performed in a bidirectional configuration where the signal is transmitted twice along the fiber in opposite directions. Experiment at 10Gb/s shows no penalty arising from the bidirectional high-power signal transmission in the fiber and demonstrates strong improvement of extinction ratio of the input signal by the regenerator.

Jitter reduction in 40 Gbit/s all-optical 3R regenerator using integrated MZI-SOA switches

Root-mean-square-phase jitter reduction from 4 to 1 ps in an all-optical 3R regenerator module operating for continuous and different length data packets at 40 Gbit/s is presented. The circuit is based on hybrid integrated Mach-Zehnder interferometric switches. Error-free operation is demonstrated with 2.5 dB power penalty improvement.

Theoretical Analysis and Experimental Demonstration of Switch characteristics of MZI Optical Switch Based on SOAs

In this paper we propose a Mach-Zehnder interferometer (MZI) optical switch based on Semiconductor Optical Amplifiers (SOAs) for all-optical 2R regeneration. Detailed investigations are presented on the characteristics of switching window of this device. Numerical simulation and experimental demonstration indicate the width of the optical pulse and the time delay between the input optical signals are essential parameters for a good performance of the device.

40-gb/s burst-mode optical 2R regenerator

We have developed a 40-Gb/s burst-mode all-optical 2R regenerator using a limiting amplifier and a monolithic integrated wavelength converter. A limiting amplifier using a gain-saturated semiconductor optical amplifier with an inverted-mode signal can mitigate the pattern effect caused by the a burst-mode signal. By using this 2R regenerator, the 8-dB packet-to-packet power fluctuation of a return-to-zero (RZ) format signal was successfully equalized and the bit-error rate was greatly improved. In addition, we confirmed that a nonreturn-to-zero format signal was equalized by the limiting amplifier as well as the RZ format signals.

All-optical multichannel 2R regeneration in a fiber-based device

We propose the design of an all-optical 2R regenerator capable of handling multiple wavelength-division-multiplexed channels simultaneously. It extends the known concept of off-center filtering of self-phase-modulation-broadened signal spectra. The novel feature of the proposed device is a dispersion map that strongly suppresses interchannel impairments. The map employs several sections of nonlinear fiber with high normal dispersion, separated by dispersion compensators with spectrally periodic group delay. The results of our numerical simulations indicate the feasibility of such a multichannel regenerator.

Field Trial of All-Optical 2R Regeneration in 40-Gbit/s WDM Transmission Systems with Optical Add/Drop Multiplexing

Optical signal processing is one of essential technologies for improving the flexibility of all-optical network. Above all, recently there have been a lot of studies regarding all-optical 2R/3R regeneration technology. However, there are few studies about all-optical 2R/3R technologies that are carried out in field environment. In this paper, we report the successful results of field trials of an all-optical 2R regeneration system based on an electro-absorption modulator for 40-Gbit/s WDM transmission systems with optical add/drop multiplexing. It was made sure that by applying the all-optical 2R regeneration system to the optical add/drop multiplexer in the 320-km-long transmission systems the transmission characteristics of the express signal after 320-km transmission and those of the dropped signal at 160-km can be made nearly the same. It is quite important that the transmission characteristics are equal for both the dropped and express channel from a point of view of the system design, and the results in this paper suggests one possible solution for this matter.

Regeneration of RZ-DPSK signals by fiber-based all-optical regenerators

Reshaping of return-to-zero differential-phase-shift keying (RZ-DPSK) signals by fiber-based all-optical 2R regenerators is numerically studied. Diffusion of the phase of the signal in the process of amplitude stabilization is assessed for two types of regenerators: one based on soliton compression followed by narrow-band filtering, and another based on ultrafast saturation of four-wave mixing (FWM) in parametric amplifier configuration. It is shown that the FWM-based regenerators induce small phase diffusion and they can improve RZ-DPSK transmission performance.

Investigation of transmission with cascaded all-optical 3R regenerators and variable inter-regenerator spacing

Transmission with cascaded all-optical 3R regeneration is reported using a reconfigurable fibre loop to investigate, for the first time, the impact of varying the inter-regenerator spacing on long-distance transmission. Error-free transmission at 10 Gbit/s over 20 000 km of standard singlemode fibre was achieved with inter-regenerator spacing range of 150-600 km, corresponding to an OSNR range of 30-23 dB/0.1 nm at the regenerator input.

A wavelength-preserving all-optical 3r regenerator

A novel all-optical 3R regenerator operated in the optically clocked scheme (OC-3R) is presented. The regenerator basically comprises two semiconductor components: an ultra-long semiconductor optical amplifier (UL-SOA) for effective use of fast nonlinearities and a self-pulsating PhaseCOMB-laser for all-optical clock recovery. The dynamic behaviour of the key devices is investigated theoretically and experimentally. An excellent regenerative performance of the assembled OC-3R is demonstrated by eye analysis and by bit error rate (BER) measurements at 40 Gbit/s.

All-Optical 2R Regeneration Using a Two-Mode Injection-Locked Fabry–PÉrot Laser Diode

We propose and demonstrate all-optical 2R regeneration using a two-mode injection-locked Fabry-Pe/spl acute/rot laser diode. We show that two-mode injection-locking can suppress the effect of relaxation oscillation and demonstrate waveform regeneration at 10 Gb/s.

BER Estimation in Optical Fiber Transmission Systems Employing All-Optical 2R Regenerators

A bit error rate estimation method for optical fiber transmission systems employing all-optical 2R regenerators is presented. The method is based on the linearization of the nonlinear transfer function of the regenerators in three sections. Using this linearized three-section model, the impact of 2R regeneration on the system performance as a function of the extinction ratio, the clamping factor, and the steepness of the transfer function is studied.

Semiconductor-based all-optical 3R regenerator demonstrated at 40 Gbit/s

A novel ‘optically clocked’ 3R regenerator (OC-3R) preserving the data wavelength and logic is presented. It is based on two compact semiconductor components, avoiding expensive and bulky EDFAs. The excellent system performance is demonstrated by eye analysis and BER measurements at 40 Gbit/s displaying a −3.5 dB negative penalty for strongly degraded signals.

10-Gb/s All-Optical 2R Regeneration Using an MQW Fabry–PÉrot Saturable Absorber and a Nonlinear Fiber

An all-optical 2R regenerator that consists of an ion implanted InGaAsP multiple-quantum-well saturable absorber, a nonlinear fiber, and an optical filter is presented. Error-free 10-Gb/s transmission over 7000 km of standard fiber with an amplifier spacing of 80 km is demonstrated in a recirculating loop experiment.

Investigation of a 2R All-Optical Regenerator Based on Four-Wave Mixing in a Semiconductor Optical Amplifier

The properties of an all-optical 2R regenerator based on four-wave mixing (FWM) in a semiconductor optical amplifier (SOA) are investigated. The regeneration is based on the nonlinear FWM transfer function and a study of the system's static behavior reveals the operating conditions, under which the transfer function approaches most the ideal, step-like discrimination characteristic function. A fiber Bragg grating (FBG) is employed in order to overcome the SOAs speed limitations due to limited carrier dynamics. The simulations with dynamic input data by means of extinction ratio (ER) and Q-factor calculations, showed satisfactory regenerative behavior up to 40 Gb/s.

Investigation of group delay ripple distorted signals transmitted through all-optical 2R regenerators

We investigate the use of all-optical regenerators to correct pulse distortions introduced by group delay ripple. Group delay ripple creates unwanted satellite pulses and intensity fluctuations. By placing an all-optical regenerator after a device that introduces group delay ripple, we show that the signal distortions can be effectively reduced. This has the benefit of opening the signal eye at the receiver. The performances of both self-phase modulation and four-wave mixing based regenerators in reducing ripple induced system penalties are examined. We find that the regenerator based on four-wave mixing achieves better suppression of group delay ripple distortions than the self-phase modulation based alternative. The eye closure penalty introduced by group delay ripple is reduced by the four-wave mixing based regenerator by 1dB.

Amplitude jitter suppression using patterning-tolerant, all-optical 3R regenerator

Investigation of the patterning tolerance and the amplitude jitter cancellation properties of a 40 Gbit/s all-optical SOA-based 3R regenerator operating with a variable optical threshold is reported. Efficient suppression of up to 3 dB peak-to-peak amplitude jitter is demonstrated for the first time at 40 Gbit/s.