Overview of DWDM/ODC Project

Abstract

This article introduces the main achievements resulting from the DWDM/ODC project. The five areas of research activity within the DWDM/ODC project cover some of the main issues of design and development of dense wavelength division multiplexing systems for transparent optical networks. These issues are: performance assessment with arbitrary optical filtering; performance of signaling formats; dispersion compensation strategies for directly and externally modulated systems in presence of nonlinear transmission-induced degradation; and the impact of noise and crosstalk in the extent of transparent optical networks. All five areas of research activity have contributed significantly to a better understanding of the limitations present in dense wavelength division multiplexing systems.     

Ultra-High-Capacity Passive Optical Network Systems with Free-Space Optical Communications

Abstract

This article experimentally demonstrates a hybrid fiber–free-space passive optical network that enables high spectral density, aggregated capacity, and total throughput through ultra-dense wavelength-division multiplexing baseband and radio-over-fiber channels. Ultra-dense wavelength-division multiplexing 10-Gb/s Nyquist-shaped 16-ary quadrature amplitude modulation, 10-Gb/s radio-over-fiber orthogonal frequency-division multiplexing, and 8.75-Gb/s baseband orthogonal frequency-division multiplexing signals per user were transmitted through a maximum 40-km passive optical network, which includes a 6-m free-space optics link with acceptable performance.     

Beyond 90-km Reach of a 16 × 2.5 Gb/s C/L-band Dense Wavelength-Division Multiplexing Metropolitan Network Based on Self-Seeded Reflective Semiconductor Optical Amplifiers

Abstract

This article reports the operation of a cost-effective, colorless, dense wavelength-division multiplexing metropolitan network based on self-seeded reflective semiconductor optical amplifiers. All reflective semiconductor optical amplifiers used in the experiments are packaged in commercial small form-factor pluggable modules. The proposal architecture is simple and symmetric thanks to utilization of two cyclic array waveguide gratings. Downstream link functions in the C-band wavelength range and the upstream link functions in the L-band wavelength range. By using erbium-doped fiber amplifiers to extend the reach, an error-free transmission over 90 km for 16 channels at 2.5 Gb/s was experimentally demonstrated for both directions, and an optical budget over 35 dB was obtained.     

Full-Duplex Link Providing Alternative Wired and Wireless Broadband Access for the Wavelength-Division Multiplexing Passive Optical Network with a Uniform Converged Signal Format

Abstract

A full-duplex link implementing alternative wired and wireless access for wavelength-division multiplexing passive optical network is proposed with the uniformed three-tone converged optical signal, which provides a wired or wireless downlink access signal alternatively and an uplink optical carrier. The uplink optical carrier reversed by the converged optical signal makes the hybrid optical node unit free from the optical source. The simulation results show that the full-duplex link with a 10-Gb/s 16-quadrature amplitude modulation (16-QAM) downstream and 5 Gb/s binary upstream can provide both wired access with a bit-error rate below 10^?9 and radio-over-fiber-based wireless access with a bit-error rate below 10^?7 over 40 km of fiber without an optical source and optical amplifier in the hybrid optical node unit.     

Overview of DWDM/ODC Project

This article introduces the main achievements resulting from the DWDM/ODC project. The five areas of research activity within the DWDM/ODC project cover some of the main issues of design and development of dense wavelength division multiplexing systems for transparent optical networks. These issues are: performance assessment with arbitrary optical filtering; performance of signaling formats; dispersion compensation strategies for directly and externally modulated systems in presence of nonlinear transmission-induced degradation; and the impact of noise and crosstalk in the extent of transparent optical networks. All five areas of research activity have contributed significantly to a better understanding of the limitations present in dense wavelength division multiplexing systems.     

Optical Filters Using Optical Multi-Layer Structures for Optical Communication Systems

Abstract

In this article, light reflection spectrums for different one-dimensional multi-layer structures are obtained. Optical reflectivities for periodic, superperiodic, and quasiperiodic structures have been calculated using the transfer matrix method. PBGs of each structure have been obtained using the optical reflectivity pattern. From a comparison of reflectivity and standard dense wavelength division multiplexing grids, it is demonstrated that narrow and dense band filters can be built from generalized Fibonacci quasiperiodic structures. Reflectivity of these structures contains bands that meet the ITU-T dense wavelength division multiplexing standard. Reflectivity of other multi-layer structures has poor or less potential to be used in dense wavelength division multiplexing systems.     

Advanced Optical Network

The following article describes an advanced dense wavelength division multiplexing (DWDM) Optical Network developed by L-3 Photonics. The network, configured as an amplified optical bus, carries traffic simultaneously in both directions, using multiple wavelengths. As a result, data distribution is of the form peer-to-multi-peer, it is protocol independent, and it is scalable. The network leverages the rapid growth in commercial optical technologies, including wavelength division multiplexing (WDM), and when applied to military and commercial platforms such as aircraft, ships, unmanned and other vehicles, provides a cost-effective, low-weight, high-speed, and high noise-immune data distribution system.     

O-Band 10-Gb/s Operation of a Reflective Semiconductor Optical Amplifier Based Self-Seeded Transmitter for Optical Access Applications

Abstract

New applications are emerging in the optical access for wavelength-division multiplexed passive optical network colorless transmitters based on a reflective semiconductor optical amplifier. Previous works have shown that 10-Gb/s operation can be reached in the C-band with such transmitters, yet trade-offs are necessary for chromatic dispersion and, consequently, link length enters the equation. Such impairments are discussed using both experimental data and simulation results. New experimental data with interesting performance in the O-band are also presented.     

A Scalable Long-Reach Wavelength-Division Multiplexing Access Network Sharing Both Fiber Protection and Broadcasting Services

Abstract

A novel scalable wavelength-division multiplexing access network is proposed in this article. By newly designing the remote node, this network can not only support the long-reach transmission and broadcasting services, it can also have flexible scalability and the ability of sharing fiber protection. These make this network have great resilient capability. Also, this scheme still has the characteristic of Rayleigh backscattering mitigation and shared-seeding light of upstream signals. The simulation results indicate this network has good performance.     

Modelling of multi-line Brillouin/erbium fibre lasers

Laser sources with unique properties can be produced using a combination of nonlinear Brillouin gain in single-mode optical fibre (SMOF) and gain in erbium-doped fibre (EDF). Narrow bandwidth nonlinear gain from stimulated Brillouin scattering in SMOF determines the wavelength of operation, and gain in EDF allows efficient operation and large power extraction. Various cascading schemes based on the Brillouin/erbium fibre laser (BEFL) as well as distinctive multi-wavelength versions of the BEFL were proposed, being able to produce 10GHz combs of over 30 lines at 1550 nm. These multi-wavelength sources may be of use in future dense wavelength-division multiplexing systems. We explore fundamental aspects of BEFLs configured to generate multiple wavelengths with particular focus on the effects of the Brillouin and EDF pumps on the number of lines and the relationship between the intensities of the individual lines in the comb.     

Broadcasting, Scalability, and Reconfigurability Aspects in an All-Optical Network Architecture

All-optical networks are a sound answer to the huge data traffic demand expected for the forthcoming information society. Interesting networking aspects are the broadcasting, scalability, and reconfiguration in an all-optical environment. These issues are addressed in the present article for an all-optical network called MATRIX, which is time slotted and uses packet switching. The architecture enables the all-optical interconnection of a large number of nodes with both a small number of wavelengths and wavelength continuity based on a consequent exploitation of wavelength-division multiplexing and space-division multiplexing (i.e., multiple fibers per cable are used). For an efficient use of the resources, each node is equipped with multiple transmitters and receivers, respectively. Two different broadcasting schemes are investigated. An analytical model is developed, and the corresponding simulation results are in good agreement. It is further shown how different networks of arbitrary size can be interconnected to larger all-optical network clusters, thereby providing scalability not only with respect to the number of nodes but also to the geographical extension. Finally, wavelength reassignments allow change of optical paths through the network in case of changing traffic patterns or network failures in order to best exploit the available network resources. The total number of possible configurations is determined by the theory of Latin Squares.     

Performance Analysis of Duty-Cycle Division Multiplexing over Wavelength Division Multiplexing System

Abstract

Performance optimization of a duty-cycle division multiplexing system over 8- and 40-channel wavelength division multiplexing networks is reported in this article. The modified duty-cycle division multiplexing system with optical domain multiplexing using a dual-drive Mach–Zehnder modulator is simulated with two and three users per wavelength. Using conventional dispersion compensation, the 40 × 40-Gbps system with two and three users per channel can support 240 and 160 km of transmission distance, respectively. The dispersion management technique based on a chirped fiber Bragg grating is proposed for a 40 × 3 × 13.33-Gbps duty-cycle division multiplexing/wavelength division multiplexing system that allows double the transmission distance compared to conventional technique.     

Novel designs for sampled grating-based multiplexers demultiplexers

Novel multiplexers-demultiplexers for dense wavelength-division multiplexing systems that use interleaved sampled gratings are presented. It is shown that, with the appropriate design, configurations ranging from hybrid to add-drop as well as all-grating-based multiplexers can easily be realized.     

Novel broadband dispersion compensating photonic crystal fibers: Applications in high-speed transmission systems

This paper reveals a novel dispersion compensating photonic crystal fiber (DC-PCF) for wide-band high-speed transmission systems. The finite-difference method with an anisotropic perfectly matched absorbing layers boundary condition is used to investigate the guiding properties. The designed novel DC-PCF shows that it is possible to obtain a larger negative dispersion coefficient, better dispersion slope compensation, and confinement losses less than 10^?4 dB/m in the entire S+C+L telecommunication band by using a modest number of design parameters. The proposed module can be used in 40 Gb/s dense wavelength division multiplexing (DWDM) systems in optical fiber communication networks.     

Non-Linear Noise Contributions in Highly Dispersive Optical Transmission Systems

This article reports an analytical investigation, confirmed by numerical simulations, about the non-linear noise contribution in single-channel systems adopting generic modulation-detection formats in long links with both managed and unmanaged dispersion compensation and its impact in system performance. This noise contribution is expressed in terms of a pulse non-linear interaction length and permits a simple calculation of the Q-factor. Results point out the dependence of this non-linear noise on the number of amplifiers spans, N, according to the adopted chromatic dispersion compensation scheme, the modulation-detection format, and the signal baud rate. It is also shown how the effects of polarization multiplexing can be taken into account and how this single-channel non-linear noise contribution can be used in a wavelength-division multiplexing (WDM) environment.     

A Pressure Sensor Using Fiber Bragg Grating

In the present investigation, a Q-switched Nd:YAG laser is used to study the various aspects of diamond processing for fabricating integrated optic and UV optoelectronic devices. Diamond is a better choice of substrate compared to silicon and gallium arsenide for the fabrication of waveguides to perform operations such as modulation, switching, multiplexing, and filtering, particularly in the ultraviolet spectrum. The experimental setup of the present investigation consists of two Q-Switched Nd:YAG lasers capable of operating at wavelengths of 1064 nm and 532 nm. The diamond cutting is performed using these two wavelengths by making the “V”-shaped groove with various opening angle. The variation of material loss of diamond during cutting is noted for the two wavelengths. The cut surface morphology and elemental and structural analysis of graphite formed during processing in both cases are compared using scanning electron microscopy (SEM) and laser Raman spectroscopy. Both the Q-Switched Nd:YAG laser systems (at 1064 nm and 532 nm) show very good performance in terms of peak-to-peak output stability, minimal spot diameter, smaller divergence angle, higher peak power in Q-switched mode, and good fundamental TEM ₀₀ mode quality for processing natural diamond stones. Less material loss and minimal micro cracks are achieved with wavelength 532 nm whereas a better diamond cut surface is achieved with processing at 1064 nm with minimum roughness.     

A Wavelength and Bandwidth Assignment Algorithm to Support Guaranteed Bandwidth Levels in Hybrid Time Division Multiplexing/Wavelength Division Multiplexing Ethernet Passive Optical Networks

Abstract

A novel bandwidth assignment algorithm in wavelength division multiplexing Ethernet passive optical networks, called a dynamic wavelength assignment service level agreement, is proposed to efficiently provide subscriber differentiation. Simulation results show that the dynamic wavelength assignment service level agreement outperforms other bandwidth allocation algorithms in wavelength division multiplexing Ethernet passive optical networks, as it makes a fairer bandwidth distribution than other methods and is able to overcome the non-allowed packet fragmentation of the Ethernet passive optical network standard. Consequently, it greatly increases the achieved throughput and always ensures a minimum guaranteed bandwidth to every priority subscriber. Furthermore, the new algorithm obtains lower mean packet delay and packet loss rate for the highest priority subscribers when compared with other bandwidth distribution schemes in wavelength division multiplexing Ethernet passive optical networks.     

Ultrafast and Wideband All-Optical Processing Technologies Towards Flexible Photonic Networks

Recent progress in ultrafast and wideband all-optical processing technologies to realize flexible and transparent optical time-division multiplexing (OTDM)/wavelength-division multiplexing (WDM) photonic networks is reviewed covering ultrafast OTDM technologies handling more than 100 Gbit/s per wavelength channel and wideband WDM technologies handling more than 1000 wavelength channels over the 200 nm range.     

A Survivable Wavelength Division Multiplexing Passive Optical Network with Both Point-to-Point Service and Broadcast Service Delivery

Abstract

A survivable wavelength division multiplexing passive optical network enabling both point-to-point service and broadcast service is presented and demonstrated. This architecture provides an automatic traffic recovery against feeder and distribution fiber link failure, respectively. In addition, it also simplifies the protection design for multiple services transmission in wavelength division multiplexing passive optical networks.     

Simulation on semiconductor optical amplifier intensity noise reduction for future spectrum-sliced optical networks

Spectrum-slicing techniques employing incoherent light are an economic, practical and therefore attractive solution for future all-optical networks, especially for wavelength-division multiplexing (WDM) transmission systems in local area networks (LAN). However, spectrum-sliced methods exhibit a large excess intensity noise factor that limits the performance of the system. In this paper, we investigate noise suppression of spectrum-sliced incoherent light using a saturated semiconductor optical amplifier (SOA). The system incorporating the noise reducing SOA is modeled and simulated using OptSim software, and the results are compared to practical schemes from the literature. Performance comparisons are made with two different broadband sources test-beds. The characteristics of the SOA gain saturation are also presented. In both cases, it is found that a high degree of intensity noise is suppressed by the use of the non-linear gain saturation characteristics of the SOA so as to achieve better system performance. The position of a modulator in the system is also investigated in order to greatly reduce the excess intensity noise.