All-optical 2R Regeneration Research Articles

Impact of RoPP in Wavelength Conversion Inducing Nonlinearity and All-Optical 3R Regeneration for DWDM Networks

Impact of RoPP in Wavelength Conversion Inducing Nonlinearity and All-Optical 3R Regeneration for DWDM Networks

Performance analysis of a cross-gain modulation (XGM) utilization in bulk-semiconductor optical amplifiers (SOAs) based all-optical 2R regeneration scheme

Performance analysis of a cross-gain modulation (XGM) utilization in bulk-semiconductor optical amplifiers (SOAs) based all-optical 2R regeneration scheme

All-optical 2R regenerator based on similariton-induced spectral broadening

We numerically investigated an all-optical high-bit-rate 2R-regenerator based on similariton-induced spectral broadening of the optical signal spectrum. The proposed configuration incorporates two cascaded regeneration stages. Active and passive generation of similariton pulses in a highly nonlinear photonic crystal fiber and a comb-like dispersion decreasing fiber are used for the first and the second stages, respectively. The study of the static behavior of the regenerator linking the design to their nonlinear power transfer functions reveals the operating conditions under which the regenerator is able to reduce amplitude noise and improve the signal extinction ratio. Furthermore, the potential of the proposed configuration is evaluated to regenerate an optical signal at 40 Gbit / s, and the 2R-regenerator is then assessed in a long recirculating fiber loop to investigate its cascadibility. The ability of the 2R-regenerator to enable operating at high-bit rates up to 160 Gbit / s is also investigated. The results demonstrate the high potential of similariton pulses for all-optical 2R-regeneration in future high-speed and long-haul transmission systems.

Verification of All-Optical Regeneration with Hybrid Modulation and with On-Off Keying Modulation with Return to Zero and Non-Return to Zero Coding

In this work we study the non-linear effects through the analysis of the operating results of three alloptical 3R regeneration (re-amplifying, re-shaping and re-timing) under the effects of cross-phase modulation (XPM) and four-wave mixing (FWM), being a system with hybrid modulation and two other communication systems with modulation on-off keying (OOK) with return to zero (RZ) and non-return to zero (NRZ) coding. The main part of the 3R regeneration system proposed here is a Mach-Zehnder interferometer (MZI) composed of an acousto optical filter (AOF) and a highly nonlinear photonic crystal fiber (HNL-PCF), so the system proposed here was named 3R-MZIAOF regenerator. The comparison of the system results occurred through the variation of the input power variation from -10 dBm to 10 dBm for the link length of 121.3 km and transmission rate 10 Gbps. The results showed that the regeneration 3R scheme OOK-NRZ with AOF presented excellent values of bit error rate (BER) equal to 10-21 and quality factor (Q-Factor) equal to 9.4, when compared to a system with OOK-NRZ 3R regeneration and hybrid modulation.

Numerical analysis of the performance of a Mach–Zehnder interferometer based on acousto-optic filter for signal regeneration

In this work we performed a numerical analysis of the performance of an all-optical 3R regenerator based on four wave mixing through a communication system Mach–Zehnder interferometer (MZI) with acousto-optic filter (AOF) and photonic crystal fiber. The frequency difference between the input signal and the pump was used as a figure of merit for comparing minimum bit-error-rate (min. BER), maximum quality factor (max. Q-factor) and optical spectrum results. In this case the non-linear Schrodinger equation was solved by the split step Fourier method. Simulation and performance analysis of the 3R-MZI-AOF regenerator were performed using OptiSystem software for systems with different frequency spacings. Therefore, with the 3R regeneration proposed here, a significant improvement in system performance was achieved, where max. Q-factor was equal to 9 and min. BER was equal to 1 × 10−19 for the 600 GHz frequency spacing and 10 Gb/s transmission rate.

All-optical 3R regeneration for DPSK signal based on a semiconductor optical amplifier scheme.

This paper presents experimental demonstration of an all-optical 3 R (re-amplification, re-shaping, re-timing) regeneration scheme for differential phase-shift keying (DPSK) signals, which consists of a clock recovery module and a phase-regeneration module. The clock recovery module is based on a mode-locked fiber laser, and the optical clock is extracted with low timing jitter of 29 ps from a degraded 10 Gb/s DPSK signal. The phase regenerator consists of a one-bit delay interferometer demodulation stage and a semiconductor optical amplifier in which cross-phase modulation and nonlinear polarization rotation occur simultaneously. The results show that, after 3 R regeneration, the receiver sensitivity is improved by more than 1.6 dB for a bit error rate of 1 E-9.

Simulation of Fiber-Optic Buffer Loop Memory with All-Optical 2R Regeneration

Structure of the fiber-optic recirculating loop memory with periodic 2R-regeneration of information flow in the optical range is designed. The modified optical fiber loop mirror for 2R-regeneration of wavelength division multiplexed return-to-zero signals is proposed. On the basis of the proposed mathematical model, using numerical modeling, the efficiency of the restoration of optical information pulses using a nonlinear optical loop mirror (NOLM) is shown. The dependences of the restoration of the signals to the required values in duration and power on the variable parameters of the NOLM (the gain of the fiber-optic erbium amplifier and the length of the nonlinear optical fiber) are obtained for 10 Gbit/s wavelength channels.

All-optical 2R-regeneration and continuous wave to pulsed signal wavelength conversion based on fiber nonlinearity

In this paper, we propose a novel all-optical 2R (re-amplification and re-shaping) regenerator based on inducing nonlinear chirp over a continuous wave probe. The regenerator also performs continuous wave to pulsed wavelength conversion. The chirp is induced in a highly nonlinear fiber by the data modulated pulsed signal that is to be regenerated. Offset filtering is employed at the output of the highly nonlinear fiber to extract the frequencies generated as a result of chirping. The regenerator performance has been evaluated with the help of bit-error-rate plots and eye diagrams at different values of optical signal to noise ratios. Apart from re-shaping and re-amplification, inclusion of the regenerator results in better resilience to amplified spontaneous emission noise.

All-optical two-channel 2R regenerator for time-interleaved PAM signals

Abstract All-optical multi-channel regeneration of advanced modulation signals is necessary for high-speed larger-capacity optical communication networks in the future from the cost point of view. As for the Mach–Zehnder-interferometer (MZI)-based pulse-amplitude-modulation (PAM) regenerator, we put forward the delay-complementary transmission scheme to avoid the crosstalk of cross-phase modulation (XPM) between two channels. The proposed scheme can ensure the optical power transfer performance required for multi-channel regeneration of time-interleaved PAM signals, regardless of differential group delay of available high nonlinear fibers. All-optical two-channel 2R regenerator for dual-wavelength RZ PAM-4 signals is established by simulation and the noise reduction ratios are up to 9.05 dB and 9.17 dB, respectively.

All-Optical 3R Regeneration Based on an Acousto Optical Filter with Q-Factor Improvement

All-Optical 3R Regeneration Based on an Acousto Optical Filter with Q-Factor Improvement

Characteristics of all-optical 3R regenerators using cascaded second-order nonlinear effect in quasi-phase matched lithium niobate devices

We numerically show that quasi-phase matched (QPM) lithium niobate (LN) devices employing the cascaded second-order nonlinear effect of second harmonic generation (SHG) and difference frequency mixing (DFM) have all-optical decision gate characteristics. The decision gate function is realized by a parabolic transmittance for a low-power region and a limiting characteristic for a high-power region. The limiter function is attributed to the large group-velocity mismatch between the fundamental and second harmonic pulses. This operation principle differs from those of other all-optical 2R (reamplification and reshaping) or 3R (2R and retiming) regenerators that have been proposed in the past. Furthermore, we show that an initial time offset between the signal and clock pulses can improve the output signal power or the switching efficiency of the device. Based on the numerical results, we propose a method for designing all-optical 3R regenerators using the cascade of SHG and DFM in the QPM-LN devices. Following the design method, all-optical 3R operation at the bit rate of 200 Gbps can be achieved using a 1-cm-long waveguide device.

ENGLISH

ENGLISH

A study of 100 Gb/s 2R regeneration for return-to-zero code signal

Quality of optical signal can be severely degraded after a long distance optical fiber transmission, therefore all-optical 2R (re-amplification, re-shaping) regeneration is required for its low power consumption and good potential of high-speed operation. Semiconductor optical amplifier (SOA) is a very promising candidate for regeneration due to its relatively low nonlinear switching power threshold and possibility of integration. However, speeds of the existing 2R schemes based on SOAs are limited by pattern effects introduced by the long carrier recovery time. So far, most of experimental results for SOA-based regeneration schemes have been limited to 40 Gb/s, only a few demonstrations at 80 Gb/s are available. An effective method to cope with the pattern effects in the SOA is to employ cross gain compression (XGC) effect. Simultaneously injecting two signals of different wavelengths with complementary logics and balanced powers into the SOA leads to an almost constant ability to make the XGC effect intrinsically immune to the pattern effects. Previously, 2R experimental results were demonstrated at 10 Gb/s and 40 Gb/s with XGC respectively, but no further results of higher speed have been presented to date. In this study, we improve the previous two-stage configuration for XGC-based regeneration by introducing a transient cross phase modulation (T-XPM) in the first SOA for generating the high-quality logic-inverted signal, which, as we find, is essential to facilitating the high-speed XGC operation in the next SOA. Firstly, a numerical model of the photon-electron dynamics in an SOA is built with considering the ultrafast intra-band processes, amplified spontaneous emission (ASE) noise at multiple wavelengths, and device segmentation along propagation direction. The quality of the logic-inverted signal with different offsets of the filter wavelength for T-XPM is studied with the model. It is found that the appropriate blue-shift detuning of the filter wavelength greatly helps to improve the quality of the logic-inverted signal. In experiment, the influence of the filter offset on the quality of the logic-inverted signal is also investigated systematically and the best quality and the largest eye-opening of the logic-inverted signal are achieved with a blue-shift of 0.72 nm, which are consistent with the simulation result. With the best logic-inverted signal, XGC effect is deployed in the second SOA. Effective reduction of the amplitude fluctuation can be observed by comparing the eye diagrams of the input degraded with output regenerative signals. Bit error rates (BERs) are also measured for all four tributaries of the degraded and the regenerated signals and the receiving sensitivity at a BER of 10-9 is improved by 1.7-2 dB. Such results show that the XGC-based 2R regeneration scheme is effective even at a speed of as high as 100 Gb/s with the help of high-quality logic-inverted signal. Degraded signals at different wavelengths (from 1535 nm to 1555 nm) are successfully regenerated with Q-factor improvement, demonstrating the wavelength-independent regeneration capability of the XGC-based 2R regenerator.

100-Gb/s 2R regeneration using cross gain compression in semiconductor optical amplifiers.

All-optical 2R regeneration of 100-Gb/s on-off-keying (OOK) signal is experimentally demonstrated based on cross gain compression (XGC) effect in semiconductor optical amplifiers (SOAs). It is shown that a high-quality logic-inverted signal and SOAs with faster gain recovery times are the two key enabling factors for obtaining regeneration results at such speeds. BER improvement of 1.2~2 dB is experimentally obtained at 1551 nm and regenerative results are demonstrated on a wide wavelength range from 1535 nm to 1555 nm. The tolerance of the input signal to optical signal-to-noise ratio (OSNR) deterioration is also experimentally studied for the 2R regeneration scheme at two different wavelengths.

All-optical four-wavelength 2R regeneration based on data-pump four-wave-mixing with offset filtering

A simultaneous all-optical 2R regeneration of 4×12.5Gb/s return-to-zero (RZ) signals is demonstrated based on the data-pump four-wave-mixing in a single highly nonlinear fiber, in which the channel spacing and duty cycle are 200GHz and 50%. Both the bidirectional configuration and time-interleaved technology are used to reduce the crosstalk from other channels. For further improving the performance of the multichannel regenerator, an offset filtering (OF) method is employed to minimize the influence from the opposite input signal. Our experiments show that the extinction ratio (ER) of regenerated signals is about two times larger than that of the degraded signals and the maximum ER improvement is about 6.5dB. By using the offset filtering method, the sensitivity improvements of four-wavelength regenerated signals are 2.05dB, 2.53dB, 3.57dB and 2.8dB, respectively.

All-Optical Low-Power 2R Regeneration of 10-Gb/s NRZ Signals Using a III-V on SOI Microdisk Laser

We demonstrate an all-optical low-power 2R regenerator of 10-Gb/s non-return-to-zero data based on a 10- μm-diameter electrically pumped microdisk laser, which is heterogeneously integrated onto the silicon-on-insulator platform and processed in a CMOS pilot line. The scheme results in BER improvement 8and works for submilliwatt-level input signals. The laser operates in the continuous-wave regime, and it is single mode at room temperature and consumes 6 mW of electrical power. Its regeneration capability is investigated in simulations and experimentally demonstrated.

Analysis of a 2R all-optical regenerator utilizing cascaded four-wave mixing in a highly nonlinear fiber

The properties of an all-optical 2R regenerator based on cascaded four-wave mixing (FWM) in a highly nonlinear fiber (HNLF) are investigated. The regeneration is based on the nonlinear cascaded 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. Numerical simulations for the regenerated temporal satellite wave with different signal and pump powers are investigated, and the optimal transfer function based on different fiber lengths and different injected wavelengths are also demonstrated.

全光2R再生器对星间DPSK调制/自差检测系统性能的改善

全光2R再生器对星间DPSK调制/自差检测系统性能的改善

Energy-Efficient Translucent Optical Transport Networks With Mixed Regenerator Placement

Translucent networks utilize sparse placements of optical-electronic-optical (O/E/O) 3R (reamplification, reshaping, and retiming) regenerators to improve the cost effectiveness and energy efficiency of wavelength-routed optical transport networks. In this paper, we show that the energy cost of a translucent network can be further reduced by leveraging the energy efficiency of all-optical 2R (reamplification and reshaping) regenerators. We propose a translucent network infrastructure that uses all-optical 2R regenerators to partially replace O/E/O 3R regenerators and implements mixed regenerator placements (MRP). We first consider the problem of MRP along a single given path, and propose three path-based impairment-aware MRP algorithms, based on periodic placement, genetic algorithm (GA), and ant colony optimization (ACO). We then address the offline network planning problem and develop a heuristic algorithm. By incorporating with one of the proposed MRP algorithms, the heuristic can achieve joint optimization of MRP and routing and wavelength assignment for high energy efficiency. We design simulations to compare the performance of different offline network planning scenarios and to see which one can provide the best balance between quality of transmission and energy cost. Simulation results show that the algorithm achieves 58.91-73.62% saving on regeneration energy, compared to the traditional scheme without all-optical 2R regenerators. The results also indicate that the joint optimization using the MRP-GA obtains the best network planning in terms of energy efficiency. Finally, we address the problem of online provisioning, and propose several algorithms to serve dynamic lightpath requests in translucent networks with MRP, and implement them in simulations to compare their performance in terms of blocking probability. Simulation results indicate that the online provisioning algorithm that utilizes the combination of the MRP-GA and a multiple MRP scheme achieves the lowest blocking probability.

40 Gb/s Optical 3R-Regeneration Based on XPM and SPM in PCF

A scheme to achieve 40Gb/s all-optical 3R-regeneration through cross-phase modulation and self-phase modulation is studied in this paper. The core of the scheme is to use ultra-highly nonlinear photonic crystal fiber as the Mach-Zehnder interference of one arm. Length of the photonic crystal fiber at the arm is adjusted after calculation so as to make the signal light through the arm produce nonlinear phase shift of by means of XPM effect, then mutual interference between the resulting light and the optical signal at the other arm is generated and the noise interfusing the system is eliminated to make the signal be regenerated. Furthermore, self-phase modulation effect of the fiber is applied to make further optimization of the signal, with Optisystem for simulation experiment.