Dense Wavelength Division Multiplexing Technology Research Articles

Dense Wavelength Division Multiplexing (DWDM) in IT Networks: A Leap Beyond Synchronous Digital Hierarchy (SDH)

The evolution of telecommunications has seen significant milestones, notably the shift from Synchronous Digital Hierarchy (SDH) to Dense Wavelength Division Multiplexing (DWDM). This transition marks a pivotal advancement in the performance of Information Technology (IT) networks, offering unparalleled improvements in bandwidth, scalability, and efficiency. DWDM technology enables the simultaneous transmission of multiple data streams across a single optical fiber by using different wavelengths of light, significantly enhancing data throughput and network capacity. This article delves into the technical foundations of DWDM, compares its performance enhancements over SDH systems, and explores its impact on modern IT network infrastructure.

Performance analysis of a hybrid optical amplifier based 480-Gbps DWDM-FSO system under the effect of different atmospheric conditions

Free space optical (FSO) systems offer a desirable and affordable way of providing communication services in remote locations. They provide secure wireless transmission without the requirement for licensing and with lower implementation costs. However, due to the impact of atmospheric turbulences on the effectiveness of FSO systems, their implementation faces significant challenges. Dense wavelength division multiplexing (DWDM) has shown promise in addressing the growing bandwidth needs in optical networks. This paper introduces a hybrid optical amplifier based system, combining DWDM and FSO technology. Energy conservation in such a system involves optimizing various aspects to reduce power consumption while maintaining or improving performance. The proposed DWDM-FSO system operates at a rate of 480 Gbps and consists of 12 channels, each capable of transmitting data at 40 Gbps. The system's performance is evaluated and compared by determining the Q-factor and bit error rate (BER) for both the cases when hybrid amplifier is employed and with no hybrid amplifier within the C-band, specifically focusing on wavelengths around 1550 nm. Moreover, the length of the FSO link is increased to assess the corresponding Q-factor and BER. Resultantly, the maximum distance for the FSO link is determined, ensuring that it remains within acceptable Q-factor and BER thresholds. Furthermore, the FSO system's effectiveness is assessed and compared across various atmospheric conditions. The findings reveal that, in clear weather conditions, the FSO system achieves a maximum distance of 510 meters while maintaining satisfactory Q-factor and BER values when not utilizing a hybrid amplifier. However, by integrating a hybrid amplifier, the system's reach significantly extends to 1700 m under clear weather conditions, still maintaining acceptable Q-factor and BER values.

Performance Analysis of Subcarrier Index Modulation OFDM in a DWDM-FSO link

Free Space Optics (FSO) is a wireless optical communication system using light to establish high-capacity links between points without the need for physical cables. However, its susceptibility to atmospheric conditions such as fog, rain, and turbulence presents challenges to signal quality maintenance. To address this, Dense Wavelength Division Multiplexing (DWDM), traditionally employed in fiber optics, is leveraged to optimize bandwidth utilization and scalability in high-capacity communications. The integration of DWDM into FSO systems offers redundancy and resilience against signal degradation induced by atmospheric conditions. To the best of our knowledge, this is the first time a paper explores the performance of the Subcarrier Index Modulation Orthogonal Frequency Division Multiplexing (SIM-OFDM) technique within a DWDM-FSO system. The objective is to reinforce FSO link robustness and improve transmission rates. Through a comparative analysis with conventional OFDM in an Additive White Gaussian Noise (AWGN) channel, the study reveals a notable Signal-to-Noise Ratio (SNR) gain of at least 3dB with enhanced SIM-OFDM (ESIM-OFDM). Simulations, conducted with realistic parameters within the DWDM-FSO architecture, demonstrate that ESIM-OFDM modulation enables a transmission range of 2 km with an aggregated rate of 10.1 Gb/s. These results underscore the potential of SIM-OFDM in enhancing FSO system performance through the integration of DWDM technology. The proposed ESIM-OFDM DWDM-FSO scenario could represent a highly interesting solution for establishing 5G Backhaul links.

Improve Quality Factor by Using DWDM Technology for Long Distances and Different Power Levels

In optical fiber communications, data travels from the transmitter to the receiver, where it is collected and converted from optical pulses into electrical signals. The need for bandwidth has grown significantly in recent years. Dense Wavelength Division Multiplexing (DWDM), an advanced multiplexing technology that allows multiple signals to be delivered simultaneously at different wavelengths in the same channel, has been developed to meet the demand for higher capacity and faster data rates. There is a decrease in signal quality as a result of the pulse expansion caused by the scattering. During long-distance transportation, scattering should be minimized. In this research, The DWDM link model uses OptiSystem 18. The DWDM design uses 48 channels, 200 GHz channel spacing, and a bit rate of 40 Gbps for each channel The link length used is 240 and 300 km, using SMF (Single Fiber Mode) and DCF (Dispersion Compensation Amplifier). The research was performed with differences in laser power of 0, 3, and 5 dBm. From the results of the analysis carried out, changes in power changes affect the performance of the system using the MRZ (Mach Zander rate) produced by a CW-10 dB laser. The laser power values correspond to the standard Q-factor and BER (Bit Error Rate) values. The highest Q-factor is 23.266 and BER is 4.66232e-0120, while the lowest Q-factor is 14.9477 and BER is 7.89923e-051. Research has shown The more laser power is used, the better the system's performance.

Modernization of Dense Wavelength Division Multiplexing (DWDM) Route Surabaya-Bangil To Increase Optical Network Capacity

Along with the increasing demand for data networks, on the Java island network traffic, especially the Surabaya - Bangil link, the operator increases the channel capacity by modernizing DWDM (Dense Wavelength Division Multiplexing) technology in its transmission equipment. At that time, the DWDM technology was DWDM 6800 with a maximum capacity of one port that could only accommodate 10 Gbit/s, while using DWDM 9800, the maximum capacity of one port could accommodate up to 100 Gbit/s. Modernization of DWDM 6800 to DWDM 9800 technology uses the cross-connect method so that it does not require many costs and can be done within a short duration of time so that network performance can be adequately maintained. As a result, after modernization, the network has sufficient reserves to cover demand for the next few years.

Entanglement distribution using a biphoton frequency comb compatible with DWDM technology.

We demonstrate a distribution of frequency-multiplexed polarization-entangled photon pairs over 16 frequency channels using demultiplexers for the signal and idler photons with a frequency spacing of 25 GHz, which is compatible with dense wavelength division multiplexing (DWDM) technology. Unlike conventional frequency-multiplexed photon-pair distribution by a broadband spontaneous parametric down-conversion (SPDC) process, we use photon pairs produced as a biphoton frequency comb by SPDC inside a cavity where one of the paired photons is confined. Owing to the free spectral range of 12.5 GHz and the finesse of over 10 of the cavity, the generated photons having a narrow linewidth in one channel are separated well from those in the other channels, which minimizes channel cross-talk in advance. The observed fidelities of the photon pairs range from 81 % to 96 % in the 16 channels. The results show the usefulness of the polarization-entangled biphoton frequency comb for frequency-multiplexed entanglement distribution via a DWDM system.

Twin-Field Quantum Key Distribution Protocol Based on Wavelength-Division-Multiplexing Technology

Quantum key distribution (QKD) generates information-theoretical secret keys between two parties based on the physical laws of quantum mechanics. Following the advancement in quantum communication networks, it becomes feasible and economical to combine QKD with classical optical communication through the same fiber using dense wavelength division multiplexing (DWDM) technology. This study proposes a detailed scheme of TF-QKD protocol with DWDM technology and analyzes its performance, considering the influence of quantum channel number and adjacent quantum crosstalk on the secret key rates. The simulation results show that the scheme further increases the secret key rate of TF-QKD and its variants. Therefore, this scheme provides a method for improving the secret key rate for practical quantum networks.

Optical Components for Transport Network Enabling The Path to 6G

The evolution beyond 5G towards 6G will accelerate the transformations begun by 5G to deploy new approaches to define delivery services. The network should be accessible anywhere, always-on and with the guarantee performances. This poses new challenges to the transport network that should assure available connectivity among the functions at different levels of granularity. The transport network should be so flexible to guarantee on-demand the connectivity among the processing functions that automatically will be required and, at the same time, should assure extreme performance. Optical network and Dense Wavelength Division Multiplexing technology are relevant candidates to match high bandwidth and low latency, but new challenges are required to assure the suitable cost and size for the wireless access networks. The current optical technology, suitable used in aggregation and long-haul transport network, cannot be simply downsized to be used in the access area, but novel paradigm should be considered for the optics as well. Integrated photonics seems a promising direction to realize low cost and low size optical components for the transport network. Moreover, this technology enables a certain level of remote tunability and reconfiguration of optical equipment that allow to simplify and reduce cost of installation in field and operation of the transport network. In this paper relevant optical components for transport networks are analyzed using the integrated photonics to assess the technology challenges.

SKKL PERFORMANCE ANALYSIS OF SUBMARINE CABLE COMMUNICATION SYSTEM (SKKL) EDFA - SOA AMPLIFIER LINK JAVA – BALI USING OPTISYSTEM

The Submarine Cable Communication System (SKKL) is a communication backbone that is deployed under the sea that used to connect networks between islands and between countries. DWDM (Dense Wavelength Division Multiplexing) technology can support long distance communication. Repeater used to reduce the impact of loss, on the detector side the signal can be detected properly. EDFA (Erbium Doped Fiber Amplifier) and Semiconductor Optical Amplifier (SOA) amplifiers can minimize the impact of loss and increasing the gain of each amplifier. The EDFA (Erbium Doped Fiber Amplifier) is an optical amplifier that can work at a wavelength of 1550 nm which provides amplification for the input signal that passes through it which is doped with the element erbium (Er). SOA amplifier is an optical amplifier that utilizes cavity or room cavity to strengthen light. By using branching unit configuration and repeaterless, repeatered, and parallel in-line amplifier configuration and optical system software 7.0 with system reliability parameters such as Q-factor, Bit Error Rate, Power Receiver, and Signal to Noise Ratio with power variations (0 dBm, 2 dBm, 4 dBm, 6 dBm, 8 dBm) at a frequency of 100 GHz for 10 channels. The best result on the Q-Factor parameter is 15,928, the BER parameter is 5.87 x 10-057, the receiver power parameter is -10,319 dBm, and the SNR is 42,713 dB. In this research the best value obtained in the Parallel in-line configuration. So as the best average is in the Repeatered EDFA configuration.

Experimental Demonstration of Wavelength-tunable In-Series DFB Laser Array with 100-GHz Spacing

We have proposed and experimentally demonstrated a four-channel wavelength-tunable in-series DFB laser array with 100-GHz channel spacing. Compared to the in-parallel laser array, the optical combiner is not utilized and the extra power loss induced by the combiner is avoided. A linearly chirped Bragg grating with multiple phase shifts implemented in the laser cavity is utilized to reduce the grating interference among different lasers. Besides, the reflector sections are inserted at two ends to provide grating feedback for two side channels. With the feedback, all the channels work with low threshold currents. The linearly chirped Bragg grating requires precise control of grating phase variation, which is quite difficult for traditional e-beam-lithography-based method. Here we used the reconstruction-equivalent-chirp technique to fabricate the grating, and precise control of the grating phase is achieved. From the experimental results, the laser arrays work with high output power (>10 mW), relative intensity noise near the relaxation oscillation frequency of below -130 dB/Hz, stable single-mode operation, and high-uniform channel spacing. Fast channel switchings (<; 600 ns) are obtained by on/off laser switching. Such laser performance enables the proposed laser array to be applied in the dense wavelength division multiplexing technology, especially when fast channel switching is needed, such as the NG-PON2 system.

Optical Cable Backbone Network Design in West Kalimantan Province Using OTN DWDM Technology

In designing the backbone network for the province of West Kalimantan using Dense Wavelength Division Multiplexing (DWDM) and Optical Transport Network (OTN) devices which cover 14 districts and cities consisting of 30 segments, of which 30 segments consist of 14 DWDM OTN sites and 8 Optical Land Amplifier sites ( OLA). From the results of the design and simulation of the backbone network, it was found that the value of the Optical Link Power Budget (OLPB) &lt; 50 dBm where this value is the ideal value in deploying a DWDM OTN backbone network, and the range of the Optical Signal Noise Ratio (OSNR) is between 20 dBm &lt; OSNR &lt; 40 dBm, which is the ideal value for OSNR, and has an Optical Rise Time Budget (ORTB) &lt; 60 ps, and also has a segment margin system of &gt; 7 dB.

A Three Demultiplexer C-Band Using Angled Multimode Interference in GaN-SiO2 Slot Waveguide Structures.

One of the most common techniques for increasing data bitrate using the telecommunication system is to use dense wavelength division multiplexing (DWDM). However, the implementation of DWDM with more channels requires additional waveguide coupler devices and greater energy consumption, which can limit the system performances. To solve these issues, we propose a new approach for designing the demultiplexer using angled multimode interference (AMMI) in gallium nitride (GaN)–silica (SiO2) slot waveguide structures. SiO2 and GaN materials are selected for confining the infrared light inside the GaN areas under the transverse electric (TE) field mode. The results show that, after 3.56 mm light propagation, three infrared wavelengths in the C-band can be demultiplexed using a single AMMI coupler with a power loss of 1.31 to 2.44 dB, large bandwidth of 12 to 13.69 nm, very low power back reflection of 47.64 to 48.76 dB, and crosstalk of −12.67 to −15.62 dB. Thus, the proposed design has the potential for improving performances in the telecommunication system that works with DWDM technology.

Design of Four-Channel Wavelength-Selectable In-Series DFB Laser Array With 100-GHz Spacing

A four-channel wavelength-selectable in-series DFB laser array with good single-longitudinal-mode (SLM) property is proposed and theoretically analyzed. To realize good SLM property, a linearly chirped Bragg grating with multiple π phase shifts are implemented in the laser cavity. In addition, two reflector sections with chirped Bragg grating are specially designed for reflection compensation at both ends. In our simulation, the split-step time-domain model with coupled-wave equations and carrier rate equations are used. Based on the simulation results, all the channels work with low threshold currents and the SLM properties are considerably enhanced compared with the conventional in-series laser array. Notably a high precision control of grating phase is required in the practical fabrication due to the ultra-small variation of grating period. Therefore, the reconstruction-equivalent-chirp technique is discussed to provide the fabrication of high-precision grating. In addition, the complex heterogeneous integration or butt-joint technique is not required during the whole fabrication process, which simplifies the fabrication and reduces the cost. The proposed wavelength-selectable in-series laser array is deemed to be applied in the dense wavelength division multiplexing technology, especially when fast wavelength switching is needed, such as in the application of NG-PON2.

Multiwavelength Q-switched erbium-doped fibre laser-based aluminum nanoparticles saturable absorber and sagnac loop filter

In this paper, we experimentally demonstrate a stable multiwavelength Q-switched erbium-doped fiber laser generation based on aluminum nanoparticles (AlNPs) as the saturable absorber (SA), with the aid of a Sagnac loop filter for the first time, to the best of author’s knowledge. The fabricated AlNPs-SA has a modulation depth, a non-saturable loss and saturable intensity of 7%, 10% and 0.0015 MW cm−2, respectively. By carefully adjusting the polarization controller and progressively increasing the pump power, up to 11 lasing lines in the Q-switching regime are obtained with a channel spacing and an optical signal-to-noise ratio of 0.48 nm and 30 dB, respectively. Meanwhile, the Q-switched performance has a minimum pulse width of 2.36 µs and a maximum pulse repetition rate of 33.45 kHz by varying the pump power to 300 mW. The proposed laser may become valuable for numerous applications such as dense wavelength division multiplexing technology.

Review and analysis of elastic optical network and sliceable bandwidth variable transponder architecture

Traditional dense wavelength division multiplexing (DWDM) technology is no longer enough to meet the extensive growth in the demand of bandwidth in an efficient and effective manner under the fixed grid environment. Thus, a technology is needed to overcome the challenges raised by the ever-increasing demand of bandwidth in an effective manner with efficient utilization of spectral resources. To solve this problem, an elastic optical network (EON) paradigm comes into existence. It uses a flexible grid technology that removes the limitations of fixed grid DWDM technology and increases the channel capacity to meet current bandwidth demand with proper utilization of optical spectrum. We present the evolution of EON from the DWDM network. We have discussed the main components and characteristics of EON that includes superchannel and sliceable bandwidth variable transponder (SBVT). Thereafter, we discuss the different modulation and transmission techniques used in EON. Next, we present the recently proposed architectures of SBVT followed by its applications. Lastly, we have discussed various subcarrier generation techniques in brief.

Розрахунок впливу нелінійних ефектів в системах DWDM на енергетичні характеристики сигналу

Nowadays DWDM (Dense Wavelength - Division Multiplexing) technology that allows increasing manyfold bandwidth capability of existing telecommunication systems and combining different types of telecommunication technologies into a single information infrastructure is being implemented actively. The main component of the DWDM system is an optical fibre. Various nonlinear effects that result in cross-interference between the optical channels and in the power reduction of the transmitted signal are created in the optical medium of signal transmissions in combination with other features of the DWDM technology. This results in lower transmission quality in the DWDM telecommunication system. Most works devoted to the research of the influence of nonlinear effects in optical fibre on the processes of propagation of the optical signal do not consider their influence on the quality of data transmission. However, the influence of nonlinear effects such as: self-phase modulation, cross-phase modulation, stimulated Raman scattering and stimulated Brillouin scattering - leads to the decrease in the power of the optical signal and, as a result, to the reduction of a signal immunity from interferences. Therefore, the main purpose of this article is to study the influence of nonlinear effects on the reduction of optical signal power in the fibre and optical noises.

Photonic-Delay Line Cross Correlation Method Based on DWDM for Phase Noise Measurement

A dual photonic-delay line cross-correlation method for phase noise measurement of microwave signal based on dense wavelength division multiplexing (DWDM) is proposed and experimentally demonstrated. The kilometer-long delay fiber is used together by the two mutually independent channels through the DWDM technology, which makes it easier to get the same delay between two channels. And it reduces the cost of the system by reducing the use of several kilometers of fiber and a Mach-Zendher modulator. Then, it uses variable optical fiber delay lines to replace the electronic phase shifters and a broader operation bandwidth can be obtained. A lower phase noise floor has been obtained by more averaging of the cross-correlation spectrum. In the experiments, the phase noise of a 10-GHz microwave signal has been measured accurately. A large operation bandwidth of 4-11 GHz is achieved and a measurement phase noise floor of -152.6 dBc/Hz at 10 kHz offset at 10 GHz in a 20 μs delay measurement system is realized by averaging 100 times.

Simultaneous frequency transfer and time synchronization over a 430 km fiber backbone network using a cascaded system

Based on dense wavelength-division multiplexing technology, frequency transfer and time synchronization are simultaneously realized over a compensated cascaded fiber link of 430 km, which is a part of the Beijing–Shanghai optical fiber backbone network. The entire cascaded system consists of two stages with fiber links of 280 and 150 km, respectively. To keep high symmetry and low noise, specific bi-directional erbium-doped fiber amplifiers are used to compensate the large optical attenuation of each fiber link. When the compensation servo is active in every stage, the cascaded system achieves the stability of 1.94×10 13 at 1 s and 1.34×10 16 at 104 s, for frequency transfer. It is also verified that the actual results of the cascaded system are in good agreement with the theoretical ones calculated from error theory. Simultaneously, after calibration of each stage, time synchronization is also realized. The final accuracy of the whole system is within 94 ps.

Thermo-Optically Tunable Silicon AWG With Above 600 GHz Channel Tunability

With the ever-increasing demand for small channel spacing in the dense wavelength division multiplexing technology, and the wavelength shift arising from the fabrication dimensional sensitivity of the silicon optical communication devices, wavelength tuning methods for silicon multiplexer/demultiplexer are therefore of great interest. Thermo-optically tunable silicon arrayed waveguide grating (AWG) multiplexer/demultiplexer using TiN heater has been demonstrated for the first time. Reduced impact of fabrication nonuniformity on the AWG effective refractive index is achieved through the waveguide design. Uniform heating is achieved by the heater design, which is analyzed by thermal distribution simulation. Above 600 GHz channel tunability has been demonstrated by simulation and experiment.

WDM PONs based on colorless technology

Wavelength Division Multiplexing (WDM) Passive Optical Network (PON) is foreseen to be part of the Next Generation Passive Optical Networks. Business and mobile fronthaul networks already express the need to develop WDM PONs in the access segment. Fixed wavelength transceivers based on Coarse WDM are already available to respond to today’s market needs but Dense WDM technologies will be needed and colorless technologies are essential to provide simple and cost-effective WDM PON systems. We propose in this paper to demonstrate the capabilities of a DWDM PON system prototype based on self-seeded RSOAs and designed to transmit CPRI over 60km of fiber at 2.5Gbit/s.