All-optical Signal Regeneration Research Articles

Modeling and design of enhanced all optical signal regeneration technique

Optical Signal regeneration in all-optical domain has played a vital in role for long haul optical communication systems. On contrary, the electronic regeneration systems have limitations in terms of real-time infeasibility for high data rate transmission with quality performance. The existing all-optical signal regeneration techniques remain in challenges for its complex design, testing and modeling prospective. The proposed all-optical signal regeneration technique is the new signal regeneration technique that is modeled and designed efficiently in order to regenerate high data rate signal that is degraded during transmission. The proposed all-optical signal regeneration technique is developed using single- pump Phase Sensitive Amplification, designed Optical Frequency Locked Model and noise mitigation model. The PSA performance is examined using various aspects i.e. signal power, noise figures, and phase error detection and correction. The proposed system will add a new dimension for signal regeneration schemes to develop more efficient regeneration systems with better performance analysis approach.

The Effect of the Nonlinearities on Gaussian Pulses Propagation in Photonic Crystal Fiber

Nonlinear effects are attributed to the dependence of the susceptibility on the electric field, which becomes important at high field strengths, in optical fibers impose different limitations on the communications link, and an understanding of such effects is almost a prerequisite for actual light wave system designers. On the other hand, they offer a variety of possibilities for all-optical signal processing, amplification and regeneration, in the nonlinear regime, is introduced and shows the influence and consequences of the nonlinear effects of the propagation Gaussian pulse in photonic crystal fibers. In this paper, one reviews the effects - both detrimental and potentially beneficial - of optical nonlinearities in photonic crystal fibers.

Development of New All-Optical Signal Regeneration Technique

All-optical signal regeneration have been the active research area since last decade due to evolution of nonlinear optical signal processing. Existing all-optical signal regeneration techniques are agitated in producing low Bit Error Rate (BER) of 10−10 at below than −10 dBm power received. In this paper, a new all-optical signal regeneration technique is developed by using phase sensitive amplification and designed optical phase locked signal mechanism. The developed all-optical signal regeneration technique is tested for different 10 Gb/s Differential Phase Shift Keying degraded signals. It is determined that the designed all-optical signal regeneration technique is able to provide signal regeneration with noise mitigation for degraded signals. It is analyzed that overall, for all degraded test signals, average BER of 10−13 is achieved at received power of −14 dBm. The designed technique will be helpful to enhance the performance of existing signal regeneration systems in the presence of severe noise by providing minimum BER at low received power.

The theoretical investigation of the impact of two-photon absorption and free-carrier absorption on phase-sensitive amplification in silicon waveguides

We investigate the influence of two-photon absorption (TPA) and free-carrier absorption (FCA) on phase-sensitive amplification (PSA) process in a dispersion engineered silicon strip waveguide at the telecom wavelengths. The phase-dependent gain and phase-to-phase transfer functions as well as the phase regeneration capacity of PSA are numerically analysed. It is found that TPA and FCA will suppress the phase-sensitive extinction ratio (PER) and the efficiency of phase squeezing. Moreover, the phase regeneration capability of silicon waveguide-based PSA is investigated by comparing the regenerated signal waveforms at a different signal power with/without TPA and FCA. Our results have potential application in all-optical signal regeneration.

A New All-Optical Signal Regeneration Technique for 10 GB/S DPSK Transmission System

<p>The transmission of high power inside the optical fiber, produce amplitude noise, phase noise and other transmission impairments that degrade the performance of optical communication system. The signal regeneration techniques are used to mitigate these nonlinear impairments in the electrical or in the optical domain. All-optical signal regeneration techniques are one of the solutions to mitigate these nonlinear transmission impairments in the optical domain without converting the signal from optical to electrical domain. The existing techniques are not capable enough to attain the Bit Error Rate (BER) less than 10<sup>-10</sup> with the power penalty less than – 9dBm. In this paper, a new all-optical signal regeneration technique is developed that mitigate amplitude and phase noises in the optical domain. The new optical signal regeneration technique is developed by combining the two existing technique one is 3R (Reshaping, Reamplification and Retiming) regeneration and other is Phase Sensitive Amplification (PSA). The 10Gb/s Differential Phase shift Keying (DPSK) noisy transmission system is used to verify the features of developed technique. The developed technique successfully mitigates the nonlinear impairments from the noisy DPSK system with significant improvement in BER at low power penalty with the additional feature of high Q-factor and an eye open response for the regenerated signal. It is determined that BER of 10<sup>-12</sup> is achieved at the power penalty of -14 dBm with Q-factor of 42 and an eye opened response. The developed technique in the DPSK system is realized using commercial software package Optisystem. The designed technique will be helpful to enhance the performance existing high-speed optical communication by achieving the minimum BER at low power penalty.</p>

All-optical wavelength conversion and signal regeneration of PAM-4 signal using a silicon waveguide.

We experimentally demonstrate on-chip all-optical wavelength conversion of 10-Gbit/s (9.35-Gbit/s net rate) 4-level pulse amplitude modulation (PAM-4) signal by exploiting degenerate four-wave mixing (FWM) in a silicon waveguide. The measured optical signal-to-noise ratio (OSNR) penalty of wavelength conversion is ~1 dB at a bit-error rate (BER) of 2 × 10-3. Moreover, the use of wavelength conversion for PAM-4 signal regeneration is also demonstrated in the experiment.

Phase-sensitive amplification in loop configuration for QPSK signal regeneration

In this paper, phase-sensitive amplification (PSA) in a loop configuration for phase regeneration of quadrature phase-shift keying (QPSK) signals is proposed. Unlike the conventional PSA schemes in which the signal output phase is locked to one of two values (e.g., 0 or π), the proposed scheme outputs signal light with one of four phase values different by π/2, owing to the loop configuration with two pump lights. All-optical QPSK signal regeneration can be achieved by using this PSA scheme.

All-Optical Signal Regenerator for Differential Phase-Shift Keying Format Employing a Differential Encoding Circuit With SOA-MZIs

We propose and demonstrate the all-optical differential phase-shift keying (DPSK) signal regenerator with differential encoder employing a newly proposed all-optical T-type flip-flop (T-FF). The proposed configuration of an all-optical T-FF employs a counter-faced configuration of two semiconductor optical amplifier Mach–Zehnder interferometers (SOA-MZIs) to realize a short feedback path without loopback waveguide for high-speed operation. Numerical simulation reveals that it can operate as a T-FF at a bit-rate of 10-Gb/s under the condition of a carrier life time of 10 ps. We also experimentally demonstrate the operation of the proposed all-optical T-FF at a bit-rate of 2 Gb/s with a fiber-based experimental setup. Finally, we demonstrate the possibility of a DPSK signal regenerator with the combination of the proposed all-optical T-FF and the standard SOA-MZI by numerical simulations, which can drastically improve the quality of a DPSK signal degraded in transmission. We believe that the proposed configuration of an all-optical DPSK regenerator is promising for future optical networks.

Fiber-Based All-Optical Signal Regeneration

Fiber-based all-optical signal regeneration techniques are reviewed. In the first half of the paper, amplitude regeneration schemes for ON-OFF keying signals using self-phase modulation and four-wave mixing in fibers are classified and their features are described. In the second half of the paper, focus is placed on regeneration schemes of phase-encoded signals. In particular, we discuss the performance of the regenerators in which phase information is converted to/from amplitude information and noise suppression is done on the amplitude. Usefulness of phase-preserving amplitude-only regeneration in reducing nonlinear phase noise is also discussed. Some experimental results are shown. Finally, issues in applying all-optical regeneration to real transmission systems are mentioned.

Enhanced Properties in Single-Walled Carbon Nanotubes Based Saturable Absorber for All Optical Signal Regeneration

Ultrafast relaxation dynamics of photogenerated carriers in nanostructure based saturable absorber (SA) are investigated using a degenerate cross-polarized pump–probe experiment at 1.55 µm operating wavelength. Single-walled carbon nanotubes (SWNT) encased in micelles are studied and compared to bundled ones as well as to iron doped InGaAs/InP multiple quantum wells (MQW). SA parameters for all optical signal regeneration (AOSR) are extracted from the normalized differential transmission. Although all samples show the same order of recombination time, SWNT in micelles present a much higher contrast ratio associated to a lower level of saturation fluence as compared to their bundled and MQW counterparts.

Design of quantum dot semiconductor optical amplifier by intelligence methods

The outstanding features of Quantum Dot Semiconductor Optical Amplifiers (QD-SOA’s) such as all-optical signal processing and signal regeneration are caused them are widely used in the optical communication systems. Due to the nano structure of these amplifiers, accurate design and modelling of them is a complex and challenging problem. This paper addresses design a QD-SOA. We present a novel method based on genetic algorithm to design QD-SOA. Since it is essential to having a model for designing, a numerical model is obtained in the first step. Then, an artificial neural network model is made using training data sampled from numerical model. The experiments show the proposed neural model has high accuracy as well as low computation time. In the next step, we convert the design problem to a genetic algorithm problem. Using neural model, the suitable fitness function is defined. The user can optimize the cost of production by setting the weight for the design parameters. The proposed system finds the best solution that satisfies desired gain regarding the production cost.

A direct comparison of single-walled carbon nanotubes and quantum-wells based subpicosecond saturable absorbers for all optical signal regeneration at 1.55 μm

Subpicosecond optical transmission experiments are used to compare saturable absorber (SA) based on bundled single-walled carbon nanotubes (SWNT) and iron-doped InGaAs/InP epitaxial multiple quantum wells (MQW) at 1.55 μm telecom wavelength. The SA key parameters (contrast ratio, saturation fluence, and recovery time) relevant for high speed all optical signal regeneration (AOSR) are extracted from the normalized differential transmission (NDT). Although both SA exhibit good contrast ratios, SWNT show a full signal recovery as well as a much faster response time than MQW. This original work on SA shows that SWNT are excellent candidates for future low cost AOSR.

A Theoretical and Experimental Study on Modulation-Format-Independent Wavelength Conversion

Modern optical networks are adopting advanced modulation formats. Future dynamic optical networks will benefit from all-optical wavelength conversion and signal regeneration techniques in support of multiple modulation formats. This paper presents a concept for a modulation-format-independent wavelength conversion technique based on an optical hybrid and an in-phase/quadrature (IQ) wavelength converter. This technique has the potential for wavelength conversion and signal regeneration of multiple modulation formats. This paper also discusses the signal distortions and noises in the semiconductor optical amplifier based IQ wavelength converter. A proof-of-principle experiment shows the wavelength conversion results of multiple modulation formats. Further, this paper presents the signal regeneration of a return-to-zero quadrature-phase-shifted-keying signal through simulation.

Wideband wavelength-flexible all-optical signal regeneration using gain-band tunable Raman amplification and self-phase-modulation-based spectral filtering

We demonstrate operating wavelength-flexible all-optical signal regeneration with 80 nm wavelength range by simply controlling the pump wavelength of the Raman preamplifier and the passband of broadened signal spectral filtering. In the operating wavelength range, improvements in receiver sensitivity of more than 2.2 dB are successfully achieved.

Timing Jitter Reduction by All-Optical Signal Regeneration Using a Polarization Bistable VCSEL

All-optical signal regeneration is experimentally demonstrated using a polarization bistable vertical-cavity surface-emitting laser. The retiming operation of signal regeneration is performed by using an AND gate operation and a reset operation. An optical clock pulse and input data signal are used for the AND gate operation. The timing jitter of the regenerated signal is reduced by optimizing the injection power ratio of the clock pulse and the data signal. The retiming operation is analyzed using a simple model that includes random fluctuation of the polarization switching threshold and bandwidth limitation of the response to the injection light.

NONLINEAR EFFECTS IN OPTICAL FIBERS: LIMITATIONS AND POSSIBILITIES

Nonlinear effects in optical fibers impose different limitations on the communications link, and an understanding of such effects is almost a prerequisite for actual lightwave-system designers. On the other hand, they offer a variety of possibilities for all-optical signal processing, amplification and regeneration. The nonlinear effects are enhanced dramatically, and new phenomena are observed in the so-called photonic crystal fibers. In this paper, we review the effects — both detrimental and potentially beneficial — of optical nonlinearities in conventional and in photonic crystal fibers.

Dispersion compensation by a tunable all-optical signal regenerator

The effect of dispersion on an NRZ signal in 120 km of SMF28 fiber is partially compensated by a tunable all-optical signal regenerator (TASR). The TASR is comprised of a semiconductor optical amplifier incorporated in an asymmetric Sagnac loop. It is shown theoretically that the primary mechanism underlying dispersion compensation in the TASR relies on its ability to control the optical phase of the carrier. Our results are supported by numerical simulations and experimental results.

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.

Tunable all-optical signal regenerator with a semiconductor optical amplifier and a Sagnac loop: principles of operation

In this paper we investigate the wavelength conversion and regeneration properties of a tunable all-optical signal regenerator (TASR). In the TASR, the wavelength conversion is done by a semiconductor optical amplifier, which is incorporated in an asymmetric Sagnac loop (ASL). We demonstrate both theoretically and experimentally that the ASL regenerates the incident signal's bit pattern, reduces its noise, increases the extinction ratio (which in many aspects is equivalent to noise reduction) and improves its bit-error rate. We also demonstrate the general behavior of the TASR with a numerical simulation.

All-optical signal regeneration by temporal slicing of nonlinearly flattened optical waveform

A novel all-optical time domain regeneration technique using nonlinear pulse broadening and flattening in normal dispersion fiber and subsequent temporal slicing by an amplitude modulator (or a device performing a similar function) is proposed. Substantial suppression of the timing jitter of jitter-degraded optical signals is demonstrated using the proposed approach.