Optical Regeneration Research Articles

Chalcogenide Glass Square Photonic Crystal Fibre with Large Negative Dispersion and High Non-Linearity

We propose a square structure, square lattice photonic crystal fibre (PCF) with square air-holes in its cladding. We consider chalcogenide (As2Se3) glass as the material of PCF. Chalcogenide glass has a large refractive index and high non-linearity compared to silica glass. A large negative dispersion of around -5473.7 ps/(nm-km) at 0.85 /um is obtained. A high non-linearity of 4813.5 W−1km−1, at telecom wavelength of 1.55µm is observed. This PCF can be used for dispersion compensation as well as non-linear applications such as non-linear switching, optical regeneration, wavelength division multiplexing, frequency conversion, super-continuum, etc.

Reducing bit-error rate with optical phase regeneration in multilevel modulation formats

We investigate theoretically the benefits of using all-optical phase regeneration in a long-haul fiber optic link. We also introduce a design for a device capable of phase regeneration without phase-to-amplitude noise conversion. We simulate numerically the bit-error rate of a wavelength division multiplexed optical communication system over many fiber spans with periodic reamplification and compare the results obtained with and without phase regeneration at half the transmission distance when using the new design or an existing design. Depending on the modulation format, our results suggest that all-optical phase regeneration can reduce the bit-error rate by up to two orders of magnitude and that the amplitude preserving design offers a 50% reduction in bit-error rate relative to existing technology.

The prospect of inter-data-center optical networks

Mega data centers and their interconnection networks have drawn great attention in recent years because of the rapid public adoption of cloud-based services. The unprecedented amount of data that needs to be communicated between data centers imposes new requirements and challenges to inter-data-center optical networks. In this article, we discuss the traffic growth trends and capacity demands of Google¿s inter-data-center network, and how they drive the network architectures and technologies to scale capacities and operational ease on existing fiber plants. We extensively review recent research findings and emerging technologies, such as digital coherent detection and the flexgrid dense wavelength-division multiplexed channel plan, and propose practical implementations, such as C+L-band transmission, packet and optical layer integration, and a software-defined networking enabled network architecture for both capacity and operational scaling. In addition, we point out a few critical areas that require more attention and research to improve efficiency and flexibility of an inter-data-center optical network: optical regeneration, data rate mismatch between Ethernet and optical transport, and real-time optical performance monitoring.

New Quaternary Sb-Se-Ge-In Chalcogenide Glasses: Linear and Nonlinear Optical Properties

Chalcogenide glasses find extensive applications in infrared (IR) devices and optical communication. Optical parameters of Sb10Se65Ge25−yIny thin films, deposited by the thermal evaporation technique, have been analyzed using ultraviolet–visible-near IR spectroscopy. The transitions in the forbidden gap are indirect. The effect of indium (In) alloying on the nonlinear optical parameters has been studied. A shift in optical absorption edge towards higher wavelength shows that the width of the localized states changes, which affects the optical parameters of the system. The high nonlinearity of these glasses makes them suitable for optical regeneration and Raman amplification.

Low-noise optical amplification and signal processing in parametric devices

Recent progress in low-noise optical amplification and signal processing has raised prospects of practical devices operating below the conventional quantum limit. We review the basic principles, practical implementation, and performance of such devices. In particular, we focus on the operation and limitations of χ(3)-based nonlinear platforms, such as silica high-confinement fiber. Classified by the parametric process application, we discuss the use of low-noise parametric mixers as optical amplifiers, phase regenerators, wavelength converters, and signal multicasters.

Field Trial Demonstration and Evaluation of a Coherent 100G IP Over WDM Alien Wavelength Across 769 km of Multiple WDM Infrastructures Without Regeneration [Invited

We report the first successful coherent 100G IP over WDM alien wavelength field trial over WDM infrastructures spanning a total distance of 769 km, demonstrating the feasibility and robust performance of a simplified 100G IP over WDM core network architecture. Key performance aspects have been investigated including co-propagation of a 100G IP over WDM alien wavelength and native wavelengths generated from WDM transponders, polarization mode dispersion tolerance, and operation without in-line dispersion compensation modules. We also demonstrated the feasibility of a 100G IP over WDM alien wavelength over multiple WDM systems and optical router or regenerator bypass. In addition, we show evaluation results on the key performance management and monitoring functions with a coherent 100G IP over WDM optical interface in the core router.

BPSK Phase Regeneration Based on Second-Order Nonlinearities in Periodically Poled Lithium Niobate

With the advance of phase modulated optical systems all-optical regeneration of Phase-Shift Keying (PSK) signals has become a key functionality for future high-speed optical networks. This paper presents a phase-sensitive optical phase regenerator for Binary Phase-Shift Keying (BPSK) signals based on direct second-order nonlinear effects in Periodically Poled Lithium Niobate (PPLN) waveguides. Analytically and through simulations, the proposed set-up is found to require lower input power for efficient operation than more complex current solutions exploiting cascaded second-order nonlinear effects, while showing lower residual noise and the prospect of efficient intensity regeneration through saturation.

Design of four-wave mixing frequency-shift-free amplitude regenerators

Frequency-shift-free all-optical amplitude regenerators based on fiber-four-wave mixing were investigated by means of simulations. These regenerators, comprised of two stages of highly nonlinear dispersion-shifted fiber, were designed using a heuristic procedure that implements a routine based on a genetic algorithm to optimize the device performance. A bit error rate improvement of up to four orders of magnitude was found as compared to a previous design approach discussed in the literature. It was due to a proper choice of the pump signal frequency regarding to the input signal that brings about a trade-off between four-wave mixing optical reshaping and four-wave mixing crosstalk leading to optimal optical regeneration. The proposed design method might be applied to other parametric devices that rely on four-wave mixing.

NRZ/RZ 40 Gbit/s optical regenerator based on a photonic two-level nonlinear device

A compact device with a two-level transfer function (TF) implemented with two semiconductor optical amplifier (SOA)-based stages is proposed and characterized. Each stage exploits nonlinear polarization rotation and self-phase modulation. The obtained improved TF with very flat top and bottom levels makes the scheme suitable for working as a reshaper in all-optical regeneration. The effectiveness of the device is verified in regenerating both nonreturn-to-zero (NRZ) and return-to-zero (RZ) data signals up to 40 Gb/s. Bit error rate measurements demonstrate increased threshold margin and extinction ratio improvement.

Performance analysis of a micro-scale pulse tube cryocooler based on optical fiber regenerator

The newly-developed holey optical fiber in photo-communication technology is introduced to the pulse tube cryocooler (PTC), exploring its feasibility as the regenerator. The influences of regenerative materials, as well as the influences of regenerator geometry, frequency, working pressure and input power were analyzed by calculating with a model based on thermoacoustic theory. The results from the simulation demonstrate that compared with the conventional stacked stainless steel screen, the utilization of optical fiber has the potential in increasing the coefficient of performance (COP) of a micro-scale PTC, as large as 0.136 at 80K. Further calculation shows the influence of working parameters on the performance of a micro-scale PTC with the optimized geometries.

基于半导体光放大器光判决门的光2R再生研究

基于半导体光放大器光判决门的光2R再生研究

Performance Evaluation of the Loop Buffer Switch Under Prioritized Traffic and Optical Regeneration

In this paper, an all-optical regenerator based, photonic packet switch architecture, which consists of the fiber loop for the storage of the contending packets, is considered. In the loop buffer, the available buffer space may not be fully utilized due to the limited re-circulation count of the data placed on buffer. This limit can be counteracted by placing a pool of regenerators inside the buffer. As optical regenerators are costly devices, hence they should be placed optimally in the buffer. The simulations results are presented by consider Prioritized and non - prioritized traffic. It is shown in the results that regeneration of data is essential if prioritized traffic has to be considered.

All-Optical Signal Processing for UltraHigh Speed Optical Systems and Networks

With high-bandwidth and on-demand applications continuing to emerge, next-generation core optical networks will likely require significant improvements in reconfigurability and ultra-fast operations. Optical signal processing overcomes the electronic bandwidth limitations with the advantages in terms of transparency and scalability. We review recent progresses in all-optical signal processing potentially for ultrahigh speed systems and networks. Starting from a brief overview of optical signal processing in high-speed optical systems and networks, we highlight a few key network functionalities, including optical logic operations, reconfigurable add/drop multiplexing, optical regeneration, wavelength conversion, format conversion, and phase-sensitive amplification. Different techniques are investigated and discussed, employing a wide range of devices and various nonlinearities. Some of experimental results are presented in both single polarization systems and polarization-division multiplexing systems.

Frequency Transfer in Electronically Stabilized Fiber Optic Link Exploiting Bidirectional Optical Amplifiers

In this paper, we present the experimental result for the fiber optic frequency transfer link with optical regenerators exploiting the same Er-doped fiber for amplifying the signals in both directions. The measurements performed at the distance of 124 km with one amplifier and 224 km with three amplifiers showed that the presented solution is adequate for transferring the frequency signals generated by cesium clocks, hydrogen masers, and cesium fountain clocks. The Allan deviation around 9 ·10-18 and 5.5 ·10-17 was found for the averaging time of 105 s for 124- and 224-km-long links, respectively.

Translucent Optical Network Planning With Heterogeneous Signal Modulation Formats

We investigate the design and planning of translucent optical networks with heterogeneous signal modulation formats. By employing multiple signal modulation formats of different optical reaches in the network, the required number of optical regenerators can be minimized. Hence, the overall network deployment capital cost and operational cost are much reduced. By building auxiliary graphs, a novel integer linear programming (ILP) is formulated to minimize the overall weighted network cost. Also, an effective heuristic is proposed to tackle networks of much larger scales. Numerical simulation studies indicate that our approach can achieve significant savings in overall network costs.

High efficiency and ultra broadband optical parametric four-wave mixing in chalcogenide-PMMA hybrid microwires

We present polymer (PMMA) cladded chalcogenide (As(2)Se(3)) hybrid microwires that realize optical parametric four-wave mixing (FWM) with wavelength conversion bandwidth as broad as 190 nm and efficiency as high as 21 dB at peak input power levels as low as 70 mW. This represents 3-30 × increase in bandwidth and 30-50 dB improvement in conversion efficiency over previous demonstrations in tapered and microstructured chalcogenide fibers with the results agreeing well with the simulations. These properties, combined with small foot-print (10 cm length), low loss (<4 dB), ease of fabrication, and the transparency of As(2)Se(3) from near-to-mid-infrared regions make this device a promising building block for lasers, optical instrumentation and optical communication devices.

Modeling of Burst Mode 2R Optical Regenerator Cascades for Long-Haul Optical Networks

A complete system-level model for cascades of burst mode 2R optical regenerators (BMOR), each consisting of an optical limiting amplifier (LA) followed by an optical reshaper, is presented for optical packet/burst-switched optical networks. The major distinction compared to continuous-mode 2R OR is that a BMOR can successfully handle the large power variations because of the LA, and the impact of inclusion of this into the system analysis is presented here. The bit error rate is evaluated along a cascade of identical BMORs, interspersed with heterogeneous inter-regenerator links (i.e., varying amplified spontaneous emission noise and net gains) which further complicate the burst mode case relative to the continuous mode. The dependency of performance of the cascade on the characteristics of the LA is investigated.

Controlling Optical Signals Through Parametric Processes

Parametric processes are capable of preserving the phase information of optical signals while their frequencies are converted. This feature, in conjunction with other basic features such as instantaneous and wideband operation, low noise, and high reliability, creates various unique functionalities in optical domain, invaluable for realizing future dynamic all optical networks that are scalable in capacity without energy crunch. This paper will review the fundamentals and proof of concept of the parametric devices that authors have been proposing as important building blocks for the future networks. The devices to be reviewed are parametric wavelength converters, parametric tunable dispersion compensators, parametric delay dispersion tuners, and wavelength-tunable optical parametric regenerators.

All-Optical 2R Regeneration With a Vertical Microcavity-Based Saturable Absorber

This paper gives an overview of recent demonstrations of optical 2R regeneration achieved by vertical microcavity mirror-based multiple-quantum-well saturable absorber (SA). The potential of the device to perform wavelength division multiplexing regeneration is first demonstrated through the first pigtailed SA chip implemented with eight independent fibers using a cost effective coupling technique. The cascadability and wavelength tunability assessment of this module associated with a power limiter fiber-based function has been experimentally demonstrated at 42.6 Gbit/s. Because this method of power limiting is not a suitable solution for all-optical multichannel 2R regeneration, a new SA structure allowing a power limiting function was proposed. We describe and characterize such a structure in this paper. This new SA opens the door to a complete passive all-optical 2R regeneration relying upon a single technology, as shown in this paper through the use of two SA: SA.0 for extinction ratio enhancement and SA.1 for high-power level equalization allowing receiver sensitivity (up to 3.5 dB) and Q-factor (up to 1.4 dB) improvement for a RZ signal at 42.6 Gbit/s. The limitation of SA.1 when the regenerator must be cascaded a large number of times is also described, leading to the observation that SA.1 should be more suitable for phase encoded formats that are more spectrally efficient than ON-OFF keying formats. A SA.1 used as a phase-preserving amplitude regenerator in a 42.6 Gbit/s RZ differential quadrature phase-shift keying transmission system is, therefore, assessed . A fiber launched power margin of 2 dB and a receiver sensitivity improvement of 5.5 dB are obtained. Finally, we use, for the first time an SA.1 as a phase-preserving amplitude regenerator of RZ differential quadrature phase-shift keying signals. The regenerator is assessed in a recirculating loop at 28 Gbaud. The system tolerance to nonlinear phase noise is enhanced by 3 dB and the distance improvement factor was 1.3 for a bit error rate = 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-4</sup> .

Service Velocity: Rapid Provisioning Strategies in Optical ROADM Networks

The advent of reconfigurable optical add/drop multiplexers with colorless and non-directional add/drop ports enables transponders and regenerators to be pre-deployed, without a priori knowledge of which wavelength or direction they will eventually serve. We study pre-deployment of optical regenerators as a means to drastically reduce the provisioning time, using Monte Carlo simulation of an optical backbone network. With appropriate placement strategies, regenerators can be efficiently pre-deployed so that new connections can be established rapidly, without the delays caused by service visits to intermediate network nodes.