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Using optical add–drop multiplexer/remover multiplexer (OADM), it is possible to add or remove wavelengths and change or route them through the various nodes and networks. At this moment, key problems in add–drop multiplexer (ADM) are the bandwidth, modulation format, and reuse wavelength. In this article, the Optisystem software simulation is used as a platform to design, test, and verify the method applied to the current work; the OADM is proposed based on the metro network to get distribution between nodes over a transmission link; OADM analysis was presented with four channels (193.1, 193.2, 193.3, and 193.4 THz) at total bandwidth of 1.6 Tb/s, none-return-to-zero (NRZ), and return to zero coding types. Experiment one shows that the average output power is −17.997 dBm, the average drop power is −17.997 dBm, and the average add power is −18.338 dBm, the average gain is −0.0429 dB, the average noise figure is 0 dB, the average power input signal is 10.679 dBm, the average of power output signal is 10.633 dBm, and the average output optical signal-to-noise ratio (OSNR) is 0 dB, However, the second experiment shows that the average output power is −24.238 dBm, the average drop power is −24.288 dBm, and the average add power is −24.753 dBm, the average gain is −0.0417 dB, the average noise figure is 0 dB, average power input signal is 7.691 dBm, average of power output signal is 7.677 dBm, and the average output OSNR 0 dB. The system supports four input channels, four add channels, four output channels, and four drop channels. The results are acceptable after three spans of Solitons fiber with 600 km length, 200 km for each span. Nonetheless, it is believed that it is well justified to adopt these schemes in the current optical network with a low cost for overall expenditure.

Performance of wavelength division multiplexing (WDM) system mostly depends on the components used in it. Optical add-drop multiplexer (OADM) is one of the most important and widely used components in WDM system used to add or drop the signals. Various types of crosstalk occurred due to the imperfections of OADM affect the WDM system performance. It is important to develop the low crosstalk or crosstalk free OADM to enhance the system performance. In this paper, we have developed an efficient OADM with low incoherent crosstalk based on coupler using isolators and Fiber Bragg Grating (FBG). We have also derived the analytical expressions for bit error rate (BER), relative intensity noise (RIN) and power penalty. It is also observed from the results that the proposed OADM has shown the better performance with lower BER and lower power penalty than the existing models while the performance of the WDM system can increase significantly.

Asymmetric duty modulation (ADM), as a recently proposed modulation scheme, provides new chance to improve the performance of dual active bridge (DAB) converter. On this basis, an optimal ADM (OADM) scheme is proposed in this article to minimize the inductor peak-to-peak current over the whole voltage and power range. First, the DAB converter adopting ADM scheme is analyzed in frequency-domain and time-domain, and four operating modes are established. Then, the minimum peak-to-peak inductor current for each operating mode is obtained under Karush–Kuhn–Tucker condition, and the corresponding optimal closed-loop control with low calculation complexity is derived. Then, the key values and features of the OADM scheme are compared with recent state of the art, mainly including the inductor root mean square current and soft-switching performance. Finally, an experimental prototype was built to validate the efficiency enhancement of the converter by adopting the proposed OADM scheme.

A full-duplex self-recovery optical fibre transport system is proposed on the basis of a novel passive single-line bidirectional optical add/drop multiplexer (SBOADM). This system aims to achieve an access network with low complexity and network protection capability. Polarisation division multiplexing technique, optical double-frequency application and wavelength reuse method are also employed in the transport system to improve wavelength utilisation efficiency and achieve colourless optical network unit. When the network comprises a hybrid tree–ring topology, the downstream signals can be bidirectionally transmitted and the upstream signals can continuously be sent back to the central office in the reverse pathways due to the remarkable routing function of the SBOADM. Thus, no complicated optical multiplexer/de-multiplexer components or massive optical switches are required in the transport system. If a fibre link failure occurs in the ring topology, then the blocked network connections can be recovered by switching only a single optical switch preinstalled in the remote node. Simulation results show that the proposed architecture can recover the network function effectively and provide identical transmission performance to overcome the impact of a breakpoint in the network. The proposed transport system presents remarkable flexibility and convenience in expandability and breakpoint self-recovery.

We assess the performance of a modular photonic integrated circuit (PIC) for space and time optical switching as an optical add-drop node for metro-access network applications. The PIC based on semiconductor optical amplifier (SOA) technology enables the implementation of compact, low cost and lossless add-dropping through fast optical switching. Data integrity measurements demonstrate error-free switching operation with less than 1 dB and 2.5 dB power penalty for 10 Gb/s and 40 Gb/s NRZ OOK optical signal, respectively. The dynamic control of the SOA based optical gates by the switch controller permits the power equalization of the switched channels. The experimental results also demonstrate dynamic forwarding, dropping and multicasting operation for a packetized 10 Gb/s NRZ OOK optical signal. The transparency of the SOA technology towards the optical signal's data rate allows to avoid costly and power consuming dedicated interfaces at the add-drop node and open a path towards efficient statistical multiplexing.

Vortex beams have application potential in multiplexing communication because of their orthogonal orbital angular momentum (OAM) modes. OAM add–drop multiplexing remains a challenge owing to the lack of mode selective coupling and separation technologies. We proposed an OAM add–drop multiplexer (OADM) using an optical diffractive deep neural network (ODNN). By exploiting the effective data-fitting capability of deep neural networks and the complex light-field manipulation ability of multilayer diffraction screens, we constructed a five-layer ODNN to manipulate the spatial location of vortex beams, which can selectively couple and separate OAM modes. Both the diffraction efficiency and mode purity exceeded 95% in simulations and four OAM channels carrying 16-quadrature-amplitude-modulation signals were successfully downloaded and uploaded with optical signal-to-noise ratio penalties of ∼1 dB at a bit error rate of 3.8 × 10−3. This method can break through the constraints of conventional OADM, such as single function and poor flexibility, which may create new opportunities for OAM multiplexing and all-optical interconnection.

Nonlinearity optimization in free space optics (FSO) transport system and the generation of 24-GHz Microwave signal based on optical add drop multiplexing scheme and external modulation technique is proposed and experimentally demonstrated. 10 Gbps/24-GHz MW signal is transmitted over 100-km (50-km+50-km) single mode fiber (SMF) distance and wirelessly communicated over 20-m by employing horn antenna, and 10 Gbps base band signal is transmitted over 100-km SMF and 10-m FSO link with the assistance of parabolic reflector, push pull amplifier (PPA) and adaptive filter (AF). The nonlinear distortion and the power loss over the FSO transmission is reduced by employing PPA and AF at the receiving end of the FSO link. Excellent bit error rate ( $${10}^{-9}$$ ), expectable eye diagram (eye height- 1.15 × 10−5 au for baseband and 1.32 × 10−5 au for 24-GHz MW) are achieved in our proposed architecture. Our presented system performed as a potential candidate for multiservice wireless network in the communication world.

In this study, radio over fiber (RoF) communications systems are analyzed. In system design, optical source, pulse generator, modulator, optical fiber, optical add drop multiplexer (OADM), amplifier and filter are utilized as communication system components. In this study, performances of various pulse generators are analyzed by OptiSystem 7.0 simulation software. Radio over fiber systems with various pulse generators are modeled and the effects of them on system performance are evaluated.

A new type of passive single-line bidirectional optical add/drop multiplexer (SBOADM) is proposed and experimentally demonstrated. When the proposed SBOADM is placed as a node of a ring topology optical fiber network, the special routing function of the SBOADM can always drop down the desired downstream signals whether the signals are injected into the SBOADM in either the clockwise (CW) or counterclockwise (CCW) direction and can upload and send back the upstream signals via the reversed optical pathway of the downstream signals. Once fiber link failure occurs in the optical network, the blocked network connections can be recovered immediately by sending out the downstream signals in both the CW and CCW directions of the fiber ring. As in all passive devices, the SBOADM needs no power supply or complicated network management to achieve the bidirectional function. Thus, the proposed device is an optimal solution to enhance the stability and reliability of rapidly developed optical fiber networks.

We experimentally demonstrate the first VCSEL-based all-optical wavelength reuse technique with reconfigurable fibre Bragg grating add and drop multiplexer. EDFA gain saturation and Bragg trans-ref...

We investigate the performance of a reconfigurable all-optical add drop multiplexer (ROADM) architecture, that is suitable of supporting high-order regular and offset based QAM signals. The design is based on a highly modular interferometric, structure, in which OFDMA sub-channels remain in the optical domain. Sub-channel extraction is achieved via waveform splitting and coherent subtraction. Numerical studies have been carried out to validate performance and optimize critical parameters of the add/drop process. Particularly, input parameters like the signal extinction ratio, pulse rise time, switching window, and input power levels have been optimized for single sub-carrier add/drop operation, from an OFDM super-channel comprising seven optical sub-carriers with 10 GHz spacing. Results have shown that the proposed ROADM architecture can accommodate and process both regular and offset based high-order QAM signals.

We experimentally demonstrate an all passive OADM using a single BGF, a pair of optical circulators and the low cost and energy efficient VCSELs. In this study, double reflection due to Bragg effect on a single fibre grating has been used to create drop and add multiplexers at 1549.9 nm wavelength with 31.4 dB wavelength isolation ratio. In performance evaluation at the 10−9 BER threshold level, a 0.3 dB add and drop receiver penalty for a 8.5 Gb/s data signal is incurred while a 0.8 dB transmission penalty is incurred for ∼25.5 km fibre distance. Using optical trans-reflectance, this paper, provides a less costly and less power consuming channel management using OADMs for high speed VCSEL transmission.

We present a compact optical add-drop multiplexer in silicon-on-insulator based on combining mode selection with Bragg reflection. The add-drop channel has a 3-dB bandwidth of 2 nm, an extinction ratio of 30 dB, and an interferometric crosstalk of less than –42 dB. We characterize the inter-channel and interferometric crosstalk performance using BER measurements for 10-Gb/s NRZ data and obtain crosstalk induced power penalties less than 3.5 dB.

In recent years, Mobile Social Networks (MSNs) have been arising a growing interest in both scientific and industrial fields for its potential value. The effective data transmission of MSNs is generally achieved through opportunistic forwarding and node collaboration. However, malicious nodes may illegally intercept and drop the data packets which should be forwarded. Therefore, it is very challenging to detect these malicious nodes. In this paper, we proposed a new Resisting On–Off Attack Data Forwarding Mechanism (OADM) for MSNs to detect the on–off attack, which not only prevents malicious nodes from intercepting data packets, but also exploits the node collaboration to forward data packets. Our major contribution includes: (1) Exploiting Hidden Markov Model (HMM) model to learn node behaviors for the evaluation of attacking probabilities and node states; (2) Effective relay node selection based the estimation of node capability. Results show the proposed OADM can effectively identify the attacking behavior and collaborating states of nodes and significantly improve the data delivery rate of MSNs.

All-optical networks transmit messages along lightpaths in which the signal is transmitted using the same wavelength in all the relevant links. We consider the problem of switching cost minimization in these networks. Specifically, the input to the problem under consideration is an optical network modeled by a graph G, a set of lightpaths modeled by paths on G, and an integer g termed the grooming factor. One has to assign a wavelength (modeled by a color) to every lightpath, so that every edge of the graph is used by at most g paths of the same color. A lightpath operating at some wavelength λ uses one Add/Drop multiplexer (ADM) at both endpoints and one Optical Add/Drop multiplexer (OADM) at every intermediate node, all operating at a wavelength of λ. Two lightpaths, both operating at the same wavelength λ, share the ADMs and OADMs in their common nodes. Therefore, the total switching cost due to the usage of ADMs and OADMs depends on the wavelength assignment. We consider networks of ring and path topology and a cost function that is a convex combination α·|OADMs|+(1−α)|ADMs| of the number of ADMs and the number of OADMs deployed in the network. We showed that the problem of minimizing this cost function is NP-complete for every convex combination, even in a path topology network with g=2. On the positive side, we present a polynomial-time approximation algorithm for the problem.

Conventionally, the phase-shift modulation (PSM) scheme is the simplest modulation scheme for a dual active bridge (DAB) converter, which only needs to control one variable to realize bidirectional power flow. However, when the input or output voltage of the converter varies widely, a large amount of reactive power is generated and the zero-voltage switching (ZVS) operation cannot be realized, which ultimately results in low efficiency. Asymmetric duty modulation (ADM), as a recently proposed modulation scheme, provides new chances to improve the performance of the DAB converter. On this basis, an optimal asymmetric duty modulation (OADM) scheme is proposed in this paper by minimizing the inductor peak-to-peak current over the whole voltage and power range. Finally, an experimental prototype was built to validate the efficiency improvement of the converter by the proposed OADM scheme.

Dual polarization quadrature phase shift keying (DP-QPSK) wavelength division multiplexing (WDM) system with 50 GHz channel spacing is currently providing various high-speed data services. The spectral efficiency (SE) of DP-QPSK WDM systems can further be increased by decreasing the channel spacing to 37.5 GHz. The 37.5 GHz frequency grid promises 33% increase in the throughput. However OADMs located at intermediate nodes in an optical network limit the performance of the 37.5 GHz, DP-QPSK WDM system. The narrowband optical filtering and crosstalk introduced by cascading OADMs limits its performance. In this paper, we presents that if the filter order of WDM multiplexer and demultiplexer is kept different it leads to an improvement in the performance of 37.5 GHz, DP-QPSK WDM optical networks. Further a significant improvement can be achieved by assigning unequal launch power on adjacent channels.

In this paper, a relatively new method called Photonic Band Gap (PBG) confinement was utilized to create an optical drop filter. Optical drop filter is a part of the optical add-drop multiplexer (OADM) which is used in the Wavelength division multiplexing (WDM) system. The 2D photonic bandgap filter was analyzed using a Finite Element Method (FEM) which shows an efficiency value of 84.7% and a Q-factor of 669 at a 1563nm wavelength. Analysis was also done to show the effect of changing various design parameters on output spectra and efficiency.

Four Wavelength Division Multiplexed 1Gb/s QAM16 streams are transmitted through 10km fiber, an Optical Add/Drop Multiplexer and a V-band beamsteering antenna with 90° steering, demonstrating the first 5G Fiber-Wireless A-RoF architecture with 360o coverage.

Wavelength-division multiplexing over optical links provides an effective solution for the bandwidth challenge of off-chip and on-chip communications. We demonstrate a compact silicon photonic four-channel optical add-drop multiplexer enabled by subwavelength-grating-based contradirectional couplers. Passbands of the device show on-chip insertion losses below 1.8 dB with wide 3 dB bandwidth of ~6.7 nm suitable for coarse wavelength-division Multiplexing in short-reach optical interconnect applications. Transmission of 10 Gb/s data stream through different channels of the multiplexer results in negligible power penalties, whereas interferometric crosstalk-induced power penalties are below 2.8 dB.

We show all-fiber-based selective mode multiplexers and demultiplexers for weakly-coupled mode-division multiplexed systems. We fabricate a set of six-mode multiplexer and demultiplexer based on fiber mode selective couplers, and experimentally evaluate the performance for the six-mode dual-polarization (DP) quadrature phase shift keying (QPSK) optical signals. In the mode multiplexer and demultiplexer, the mode couplings between the lower three modes and the higher three modes are suppressed to be less than −20 dB, which enables us to apply partial 6 × 6 MIMO equalizers even for the six-mode demultiplexing. For the six-mode DP-QPSK signals, the penalty of optical signal-to-noise ratio by replacing the full 12 × 12MIMO to the partial 6 × 6 MIMO is suppressed by less than 1 dB.

This paper proposes a hybrid ring- and tree-topology radio over fiber (RoF) transmission system with self-disconnection protection that can support the high distribution density of base stations (BSs) in a metropolitan area and strengthen the network quality of service through self-disconnection protection. The number of supportable BS in the system can be increased significantly by integrating the time- and wavelength-division multiplexing techniques and properly utilizing a new-generation single-line bidirectional add/drop multiplexer (SBOADM) into the proposed system. Moreover, when the ring–fiber link of the system is interrupted for any reason, the system operator can recover the broken connections quickly only by transforming an optical switch state at the CO end to allow the downlink optical signals to transmit along the clockwise and counterclockwise directions of the ring–fiber link simultaneously. In this case, the downstream optical signals can be delivered to each set of BS-groups through the two-way transmission characteristics of the SBOADM automatically, and the uplink optical signals, originally, from each set of BS-groups can be transmitted back to the CO end along the opposite direction of the downlink signal-routing path. In this way, the interference caused by fiber breakage can be avoided immediately, and the entire transport system can be reconnected to ensure the quality of network services. Our experimental results prove that the overall transmission performances are similar to those under normal circumstances.

The optical cross add and drop multiplexing (OXADM) node described in this paper increases the capacity, flexibility and reliability of the trunk-line optical network used for data communication. It features two different bandwidths which operate in working and protection line in a ring configuration. The OXADM has the same features of the conventional OADM node but with more efficiency and reliability. The OXADM prototype system focuses on providing survivability through restoration against failures, such as cable/fiber cut in optical layer with ring topology. Two types of restoration scheme have been proposed to ensure data flow continuously by means of linear/ multiplex protection and ring protection. Comparison between OXADM and OADM restoration schemes is also described. The BER characteristics were measured at 2.5 Gbps (OC-48) and small degradation was observed, as confirmed by a comparison of these simulation results with those obtained from systems without restoration element. Restoration schemes in OXADM node are more reliable and efficient compare to conventional device due to internally routing mechanisms and no ‘drop and re-add function’ is needed to route the signal to alternative path or processed the signals in both electronic and optical domain as practice in conventional nodes today.

An 8 × 25 -Gb/s optical time-division multiplexing (OTDM) system is demonstrated experimentally. The optical pulse source is based on optical frequency comb (OFC) generation and pulse shaping, which can generate nearly chirp-free 25-GHz 1.6-ps optical Gaussian pulse. The eightfold optical time-division demultiplexer consists of a single-driven dual-parallel Mach–Zehnder modulator (DPMZM) and a Mamyshev reshaper. Error-free demultiplexing of 8 × 25 -Gb/s back-to-back (B2B) signal with a power penalty of 4.1 dB to 4.4 dB at a bit error rate (BER) of 1 0 − 9 is achieved to confirm the performance of the proposed system.

Advanced modulation formats like dual-polarization quadrature phase-shift keying (DP-QPSK) along with the digital coherent receiver are enabling optical networks to provide high spectral efficiency (SE) over long-haul transmission reach. The DP-QPSK based dense wavelength division multiplexing (DWDM) system with 37.5 GHz channel spacing can provide extra throughput of 33% compared to 50 GHz channel spacing. However, at 37.5 GHz channel spacing, optical add-drop multiplexers (OADMs) at intermediate nodes, impact the performance of WDM based optical networks in terms of increased BER, thereby reducing transmission reach drastically. In this paper, we have analyzed with the help of numerical simulations, the performance of a differentially encoded eight-channel 112 Gb/s, OADM based DWDM optical network with a channel spacing of 37.5 GHz. We propose that the selection of optimum values of system parameters can result in reducing the impact of crosstalk propagation and narrowband optical filtering introduced by a chain of OADMs at 37.5 GHz channel spacing. The paper exhibited that the selection of optimum values of parameters like filter order of multiplexer and demultiplexer, launch power per channel and filter taps of adaptive equalizer (AE) result in achieving minimum BER on all the channels over a long transmission reach up to 3600 km.

The advent of nodal elements, such as Optical Add/Drop Multiplexers (OADM) for Wavelength Division Multiplexed (WDM) networks, has led to a myriad of possible network architectures for the optical layer. In this project we design and simulate a WDM-OADM optical ring system of four nodes, two wavelengths on unidirectional single mode fiber at data rates of up to 10 Gbps. We use a continuous wave laser as a source for each channel with external modulation. The performance of the system is reported on the basis of eye diagram, Bit Error Rate (BER) and Q-factor. Optisystem software is used to simulate the overall designed system.

Space-division multiplexing is expected to be a key technology both for dealing with the future capacity crunch facing traditional single- mode fiber and for realizing a sustainable optical network that can accommodate the various data streams originating from, for example, future 5G communication, the Internet of Things, and machine-to-machine networks. This article describes the potential of space-division multiplexing as regards optical fiber and cable technology. We focus on the potential of multi-core fiber and investigate the reality of multi-core-fiberbased space-division multiplexing optical wiring as the first example of a space-division multiplexing application taking the latest research and development into consideration. Finally, we show that the key technology behind multi-core-fiber-based space-division multiplexing optical wiring is ready for discussion as a near future standard.

The development of mode division multiplexing has found numerous interesting applications in optical sensing. A major challenge has been how to control the mode composition of the interrogation signals. In this work, we presented a time-domain method that can adaptively control the form of optical signals at multiple locations in a two-mode-fiber. We also carry out a preliminary study that suggests the method of adaptive mode control is compatible with the requirements of optical sensing.

We demonstrate a four-port optical switch for the fat-tree photonic network-on-chip architecture, which contains four silicon Mach–Zehnder optical switch elements tuned by the plasma dispersion effect. The optical signal-to-noise ratio of the device is over 10.0 dB in the wavelength range from 1525 to 1565 nm. The routing functionality of the device is verified and 50- × 32-Gb/s wavelength-division-multiplexing data transmission for one optical link is demonstrated. The rise and fall times (10%–90% and 90%–10%) of the optical switch element are both ∼2 ns. The average power consumption of the device is ∼56.8 mW.

A novel three-stage all-pass filter (APF) is proposed as a tunable optical delay line to construct an optical time division multiplexer (OTDM), with which, we can get ultrahigh bit rates with several low-speed channels. The proposed design mitigates the deleterious effects of group delay dispersion and provides wide bandwidth with small ripples and continuously tunable long delays achieved with small variations in the effective refraction index, making it suitable for high-speed optical networks on chip.

A mode multiplexer/demultiplexer based on two mutually spliced tapered multi-core fiber is proposed in this letter. Mode multiplexing occurs in the tapered region, and it is less sensitive to wavelength and structure parameters. Simulation results show that mode multiplexer/demultiplexer for LP01 and LP11 mode exhibited a coupling efficiency greater than 90% over the wavelength bandwidth of 760 nm. Mode multiplexer/demultiplexer for LP01 and LP21 mode exhibited a coupling efficiency greater than 85% over the wavelength bandwidth of 320 nm.

Environmental perturbations, such as wind, mechanical stress, temperature, and lightning, impose microsecond-time-scale changes to the transfer matrix of a multimode fiber (MMF), necessitating adaptive multiple-input multiple-output (MIMO) equalization to track the time-varying channel. It is of significant interest to accurately model channel dynamics so that adaptive MIMO equalization algorithms can be optimized and their impact on digital signal processing complexity and performance can be assessed. We propose a dynamic channel model using coupled-mode theory to describe time-varying polarization- and spatial-mode coupling in MMF caused by fast environmental perturbations. Our method assumes that the MMF has built-in refractive index and geometric defects that are responsible for random birefringence and mode coupling. Various time-varying perturbations modify the coupling coefficients in the coupled-mode equations to drive channel dynamics. We use our dynamic channel model to simulate an example aerial fiber link subject to a sudden gust of wind and show that increasing the strength of the perturbation, the number of modes, and the length of exposed fiber all lead to higher error at the output of an adaptive MIMO equalizer. We employ the model to study the convergence and tracking performance of the least-mean-squares adaptive equalization algorithm.

A large-scale multilongitudinal mode fiber laser sensor array is proposed and demonstrated experimentally based on wavelength/frequency division multiplexing and beat frequency demodulation technique. In the proposed hybrid multiplexing sensing system, the frequency division multiplexing is realized by designing n fiber lasers with different cavity lengths, while the wavelength division multiplexing is achieved by incorporating a 1 × m coupler and an m -channel wavelength division demultiplexer. By making the operating wavelength of frequency-multiplexed lasers equal to the central wavelength of each channel in the demultiplexer, the light of each laser is coupled independently to the corresponding channel. Therefore, the multiplexing capability of the multilongitudinal mode fiber laser sensors is greatly improved and the maximum number of multiplexed sensors is m × n theoretically. To verify the proposed wavelength/frequency division multiplexing system, a 4 × 4 multilongitudinal mode fiber laser sensor array was set up and investigated. Experimental results show that there is a low crosstalk between the adjacent channels. The proposed wavelength/frequency hybrid multiplexing technology has the ability to monitor simultaneously a large number of fiber laser sensors.