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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.

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.

We demonstrate an ultra-dense wavelength-division-multiplexing (UDWDM) passive optical network (PON) in a spatial-division-multiplexing system utilizing our home-made seven-core multicore fiber (MCF) with a self-homodyne coherent detection (SHCD) scheme. In the SHCD system, we transmit 12 channels of 40-Gb/s UDWDM-PON signals using polarization-division-multiplexing quadrature phase-shift keying (PDM-QPSK) with a 12-GHz grid through the six outer cores of the seven-core MCF with the central core used to transmit the pilot tone. An optical frequency comb generator is employed to supply the multi-carriers for cost saving. After 37-km low-crosstalk seven-core MCF long-reach transmission with compact fan-in/fan-out multiplexers, a large transmission capacity of 2.88 Tb/s and a power budget of 26 dB are obtained. At the optical network unit side, a narrow linewidth local oscillator laser is no longer necessary since SHCD is adopted in our system. The complexity of the digital signal processing procedure at the coherent receiver is also greatly reduced as the carrier phase recovery and carrier frequency offset estimation are not needed.

Wavelength reuse has been proposed as an effective solution to realize colorless optical network units (ONUs) for next-generation passive optical network with simplified maintenance and reduced cost. In this paper, we propose a wavelength reused mode-division-multiplexing (MDM) scheme for bidirectional short-reach optical access network with low mode-crosstalk multiplexer/demultiplexer (MUX/DEMUX) and few-mode fiber (FMF). In downstream (DS) transmission, one of the spatial modes in FMF is used to transmit optical carriers, while the others are used as DS signal channels. In upstream (US) transmission, the carrier is split to all the ONUs for US remodulation. By utilizing low mode-crosstalk mode MUX/DEMUX and FMF, the carrier and each signal channel can be effectively separated. Compared with other wavelength reused schemes in which the DS and US transmission are modulated in orthogonal dimension, the signal qualities on two transmission directions are independent in the proposed scheme, and symmetrical bidirectional transmission without residual remodulation crosstalk can be achieved. What is more, to reduce bidirectional Rayleigh backscattering noise, we propose to use different optical sidebands for DS and US transmission. With the proposed scheme, we experimentally demonstrate symmetrical bidirectional 2 × 12.5-Gb/s quadrature phase-shift keying (QPSK) orthogonal-frequency-division-multiplexing (OFDM) intensity-modulation and direct-detection transmission over 11.5-km four-mode FMF. With Rayleigh backscattering noise mitigation, a Q-factor improvement of 2 dB is achieved for the US signal at the DS signal-to-carrier power ratio of -27 dB.

We experimentally and via simulations demonstrate ultracompact single-stage and cascaded optical add-drop multiplexers using misaligned sidewall Bragg grating in a Mach–Zehnder interferometer for the silicon-on-insulator platform. The single-stage configuration has a device footprint of 400 ${\mu }\text{m}\,\times$ 90 ${\mu }\text{m}$ , and the cascaded configuration has a footprint of 400 ${\mu }\text{m}\,\times$ 125 ${\mu }\text{m}$ . The proposed designs have 3-dB bandwidths of 6 nm and extinction ratios of 25 dB and 51 dB, respectively, and have been fabricated for the transverse electric mode. A minimum lithographic feature size of 80 nm is used in our design, which is within the limitation of 193 nm deep ultraviolet lithography.

We investigate the network performance of FOADM based metro access network with edge computing to fulfil the critical requirement in 5G networks. NFV and network slicing are considered in the model to emulate realistic operation.

We demonstrate an optical add-drop multiplexer on the silicon-on-insulator platform with a 3 dB bandwidth of 6.3 nm, an ultra-high adjacent channel isolation of 58 dB, an insertion loss of 0.8 dB, and a footprint of only 1882 μm2.

We present designs of wavelength-division-multiplexing (WDM) and mode-division-multiplexing (MDM) optical links using mode de/multiplexers (DE/MUXs) based on multimode interference (MMI) couplers with a tilt joint as a phase shifter. The properties of WDM-MDM links with three wavelengths and two optical modes are numerically studied by using 3-D beam propagation method. In the first design, the wavelength combiner is also an MMI coupler type. The insertion loss of the design is around 6 dB because of the inherent loss of the MMI combiner. The size of the main passive optical parts (mode DE/MUXs and wavelength combiner) of the design is only 10.4 × 114.2 μm2, making the design promising for future compact and high-capacity optical interconnection applications. In another design, arrayed waveguide gratings are used for wavelength multiplexing, leading to a lower insertion loss of the optical connections. For both designs, the mode crosstalk between the two different modes for the same wavelength are below -22 dB.

In this paper, we proposed a cost-effective broadcast signal transmission scheme using a distributed feedback laser diode (DFB-LD) for wavelength-division-multiplexing passive optical network (WDM-PON) systems. The DFB-LD is directly modulated with a single-tone radio frequency signal to generate multiple optical carriers. An optical signal-to-noise ratio (OSNR) is enhanced using a delay interferometer as a double-pass interferometer. Orthogonal frequency division multiplexing (OFDM) and on-off keying (OOK) signals are experimentally demonstrated to test the broadcasting scheme. We measured the bit-error-rate (BER) and the power penalty after the broadcasting OFDM and OOK signals are transmitted through a 25-km single-mode fiber. An excellent performance of BER is achieved for both OOK and OFDM signals. The proposed scheme is a practical and cost-effective solution for broadcast signal transmissions in WDM-PON systems.

We demonstrate a silicon-based wavelength-division multiplexing (WDM) tree splitter for optofluidic switching of nanoparticles in a lab-on-a-chip or nanofluidic system. The gradient force and scattering force induced by the evanescent field can, respectively, lead to trapping and transportation of colloidal polystyrene (PS) spheres directly above the waveguide. Guiding of PS into any designated branch within a cascaded tree splitter is achieved by switching of the excitation wavelength. As compared to that based on microrings, an optimized design of the reported tree splitter approach offers a number of advantages in terms of device compactness, wavelength tolerance, response speed, and trap stability, while maintaining the inherent low-loss and low-power performance features of WDM splitters. A network of such splitters can readily lead to a platform for high-throughput and large-scale particle manipulation in nanofluidic systems.

This paper represents an analytical expression for Incoherent crosstalk of optical add drop multiplexers (OADM) with Mach-Zehnder interferometer (MZI) based on coupler and fiber Bragg grating (FBG). Analytical expressions for relative intensity noise (RIN), power penalty (PP) and bit error rate (BER) have been derived to analysis the incoherent crosstalk for this model. Results of the analysis show less crosstalk, low relative intensity noise, low power penalty and low bit error rate when a signal with Bragg wavelength is added. Performance of the model is also better than the current models.

Wavelength division multiplexing (WDM) is an efficient method where several channels are transmitted through a single optical fiber. But performance of WDM system degraded due to the imperfections of different components used in it. Fiber Bragg grating and circulator (FBG-Circulator) based optical add-drop multiplexer (OADM) is the most important component used to add or drop the signals in WDM system. In this article we analyzed the coherent crosstalk of FBG-Circulator based OADM with respect to power penalty, bit error rate (BER), and photo current and analytical models also have developed. Satisfactory system performance have ensured when signals with Bragg wavelength are added. From the results it also shown that the performance of FBG-Circulator based OADM is better than other existing OADMs.

An optical add-drop multiplexer (OADM) filter configuration based on a single microring is designed, fabricated and experimentally demonstrated for O-band communications. The influence of the waveguide width is carefully analyzed to design the optimum coupling factor while keeping the minimum ring length. In such a way, the FSR is maximized while insertion losses below 1dB and extinctions ratios higher than 20dB are ensured.

An eight-channel integrated optical add-drop multiplexer with cascaded parent-sub microring resonators is experimentally demonstrated on a silicon-on-insulator (SOI) substrate. Through thermal tuning, each channel can be independently switched between the adding and dropping states. The measured thermal tuning efficiency is 0.15 nm/mW. Typically, all eight channels can be multiplexed and demultiplexed with a 2.6-dB drop loss, a 0.36-nm bandwidth ( $>$ 40 GHz), and a $-$ 20-dB channel crosstalk. Moreover, the scheme to increase the number of operating channels is also discussed.

In this paper, we propose and experimentally demonstrated a novel passive optical network access architecture based on orbital angular momentum (OAM) multiplexing. Multiple data channels are multiplexed by orthogonal OAM modes on the same wavelength to achieve efficient utilization of bandwidth resources. Twenty OAM modes, with each mode carrying 10-Gb/s on-off keying signal, are transmitted over 0.4-m free-space optics link. The bit error ratio (BER) performances of all data channels can be under a 3.8 × 10-3 enhanced forward error correction limit. The experimental results show the potentiality of the proposed architecture for providing user access with flexibility and bandwidth efficiency in future ultrahigh-capacity passive optical networks.

We fabricate and demonstrate on-chip two-mode (de)multiplexing using a tapered asymmetrical grating-assisted contradirectional coupler-based $\text{TE}_{0}$ and $\text{TE}_{2}$ mode multiplexer and demultiplexer on the silicon-on-insulator platform. The designed silicon photonic device is composed of apodized grating couplers, a narrow waveguide, a bus waveguide, and an asymmetrical multimode grating-assisted contradirectional coupler. The operation principle of such a mode (de)multiplexer is analyzed according to the coupled mode theory. System experiments of orthogonal-frequency-division-multiplexing-based offset quadrature amplitude modulation (OFDM/OQAM) 256-ary QAM data transmission have been carried out for two-mode (de)multiplexing application at 23.89 Gbit/s. The bit error rate (BER) performance for the signal transmission through the fabricated two-mode (de)multiplexer is evaluated. The optical signal-to-noise ratio (OSNR) penalties of data transmission through the fabricated two-mode (de)multiplexer are less than 2 dB at a BER of $2\mathrm{e}^{-2}$ (20% forward error correction threshold).

In this paper, a flexible and reliable 40-Gb/s time and wavelength division multiplexing passive optical network (TWDM-PON) architecture is proposed and demonstrated. Here, a $4\times 10\ \mbox{Gb/s}$ orthogonal frequency-division multiplexing (OFDM) downstream signal is achieved by utilizing four 2.5-GHz directly modulated lasers in the optical line terminal. A reflective optical semiconductor amplifier is utilized in each optical network unit to serve as upstream transmitter (Tx) transmitting 2.5-Gb/s on-off keying (OOK) and 10-Gb/s OFDM upstream traffic, respectively. In addition, the dynamic bandwidth (capacity) allocation and fiber fault protection also can be achieved by applying the new proposed PON architecture with software-defined networking approach.

We show cascaded 100-Gb/s sub-channel add/drop from a 1-Tb/s MB-OFDM or Nyquist-WDM super-channel having ultra-low inter-sub-channel guard-bands within a recirculating loop via a hierarchical ROADM using high-resolution filters, showcasing up to 1000-km transmission reach and five ROADM node passages for the add/drop sub-channel when hybrid Raman-EDFA is used.

In this paper, a new structure of optical add-drop multiplexer based on cascaded phase shifted linearly chirped fiber Bragg grating (CPSLCFBG) and Mach-Zehnder Interferometer (MZI) is proposed. The spectrum of drop port and output port of the OADM is analyzed using transmission matrix method by optimizing of CPSLCFBG with Cap apodization function. At the port of the drop and the output, which has equidistant multi channels with almost equal output power and very narrow bandwidth, even about 40 channels, and the transmission performance is very good.

We propose a WDM and MDM compatible 2×2 switch on a silicon chip. It is composed of mode multiplexers, 2×2 single mode optical switch elements, and mode de-multiplexers. We demonstrate a prototype which can manipulate four spatial modes with broad wavelength span.

A single-line bidirectional optical add-drop multiplexer is proposed to provide ring-based passive optical network with a self-healing functionality to eliminate the effect of any one fiber failure.

Space-division multiplexed (SDM) systems use multiple spatial-paths in multimode or multi-core fiber to increase the capacity and/or photon-efficiency carried by an optical fiber. For SDM systems to be competitive, they must outperform or have a cost advantage over parallel single mode fiber systems. The cost advantages can come from spatial integration where many spatial channels can be processed by a single device. We will show enabling components such as wavelength-selective switches and optical amplifiers for various types of multimode fiber.

The dramatic increase in demand for services that require high bandwidth and augmented bitrate to function properly has become a trend in recent years. In order to comply with the current demand, telecom companies struggle to enlarge the offered capacity as well as to minimize the latency and to enhance the reliability of the network. An effective technique to increase the capacity is to move to higher frequency bands, such as millimeter wave band, where the inherent features promise larger capacities and less interference. The other proven method to increase the capacity is to incorporate optical coding in conjunction with the guidelines of optical code division multiple access (OCDMA) where the number of users is increased based on the assignment of optical orthogonal codes to every user. Finally, through the application of multiple wavelengths to transmit optical encoded signals in multiple channels, as suggested by the wavelength division multiplexing (WDM) scheme, the capacity can be increased substantially. In this paper, a W-band WDM-over-OCDMA system is presented. The simulation results show the effect of various optical codes, profiled in a superstructure fiber Bragg grating (SSFBG) device as encoder/decoder, and wavelength channels on the BER versus the received optical power.

In this research, the design of submarine cable communication system for East Nusa Tenggara was made. There are five nodes in the design which is Ende, Larantuka, Kalabahi, Atambua, and Kupang based on Palapa Ring network plan map. The system is designed to handle data traffic of East Nusa Tenggara up to year 2030. Four links are designed which is Ende-Larantuka, Larantuka-Kalabahi, Kalabahi-Atambua, and Atambua-Kupang. Based on traffic forecasting, the traffic demand of the five nodes on year 2030 is 90.3 Gbps, which consist of 58.64 Gbps traffic traversing between nodes. 6λ of DWDM STM-64 channels with 10 Gbps datarate each is required to accomodate the demand of two-way transmission. The total length of cable required is 882.71 km which consists of 137.09 km terrestrial cable and 745.62 km submarine cable. The design uses OADM. One repeater is required for each Ende-Larantuka, Larantuka-Kalabahi and Atambua-Kupang links since the optical power at the receiver on each of the three links is below the minimum allowed value. Power feeding equipments are placed on those three links to supply power to the repeater. DCF is used to compensate dispersion. Performance analysis shows that the design complies with power budget, rise time, and OSNR criteria.

As optical switching and multiplexing architectures evolve, optical multicast keeps on being a capability advertised by a few core and transport optical equipment vendors. However, to the date, not much use of this service has been made by operators. This work addresses the reasons behind this fact, identifies the key technical design factors in a multicast-capable network and the challenges to face for an effective use of multicast at the optical layer.

With deployment and continuous development of optical routes, the issues concerning the thermal loading of erbium-doped optical fibres become more and more relevant. As we were able to see a significant expansion of optical communication systems in the recent years, it was also necessary to find ways for bridging longer distances between individual points of the optical route. Modern optical telecommunication routes mainly use the DWDM system and optical transmission in the C and L bands. For this purpose, optical amplifiers that are mainly based on erbium doping are used. The aim of this paper is to point out the issues associated with the implementation of erbium-doped amplifying fibres into optical transmission routes that are made using the WDM-PON technology, with regard to the thermal load of these amplifying fibres.

In optical telecommunication technology the capacity of the transmission bandwidth will soon be achieved [1]. In addition to the wavelength, polarization and phase of the light, one can increase the spatial dimension of the optical fiber core as a fourth degree of freedom to enhance the transmission capacity. This can be done by increasing the diameter of the fiber core itself and, hence, applying multi-mode fibers or even by using a fiber with multiple cores. These approaches are summarized as spatial division multiplexing (SDM) [1]. One form of SDM is the mode division multiplexing (MDM) [2]. In MDM, different field modes are used as individual transmission channels. Besides the use of few mode fibers (fm-fibers) a key challenge to enable MDM lies in the development of mode selective coupler structures.

In this study, we design and fabricate an optical interleaver using arrayed waveguide gratings (AWGs). The characteristic of AWGs which is a large channel spacing between two adjacent wavelengths in the same channel, so we can reliably through the tunable fiber Bragg grating (TFBG) to filter. Through the tunable FBG, the reflected wavelength signal, which we want to get, can be sent to the output port. We can also use the optical circulator (OC) to add the wavelength signal from the add port to join the original network routing. This system can also be used to achieve an all-optical multichannel reconfigurable optical Add/Drop multiplexer (ROADM) system.

With the fast development of various applications, the demand for network bandwidth has been increasing significantly during the past decade. Although the WDM (wavelength-division multiplexing) technology has already provided high bandwidth using parallel wavelength channels, the overall network spectrum efficiency is however severely discounted by the fixed grid definition and standard rate transmission. The short-term solution to increase capacity is by introducing hardware enabling elastic optical networking (EON), which is intrinsically related to flexible-grid channel allocation; and the longer-term solution involves extending the fiber capacity by space division multiplexing (SDM) based on new types of fibers supporting multiple cores, multiple elements, few LP modes or even modes carrying Orbital Angular Momentum (OAM). Moreover, for short-term evolution, it may not be economically viable to make a one-time complete upgrade to full flexible-grid technology on the entire network, which means, before the current optical transport network capacity is exhausted, the current fixed-grid network could be maximally kept operational during the migration to preserve the already-made investment. In this talk, a series of topics will be discussed, such as the network architecture with co-existing fixed-grid and flexible-grid technologies, migration strategies evolving from fixed-grid to flexible-grid, SDM based Reconfigurable Optical Add/Drop Multiplexers (ROADMs), as well as networking aspects of routing and spectrum resource allocation when considering spectral/spatial switching.

We present detailed electrical and optical models of the elements that comprise a WDM silicon photonic link. The electronics is assumed to be based on 65 nm CMOS node and the optical modulators and demultiplexers are based on microring resonators. The goal of this study is to analyze the energy consumption and scalability of the link by finding the right combination of (number of channels × data rate per channel) that fully covers the available optical power budget. Based on the set of empirical and analytical models presented in this work, a maximum capacity of 0.75 Tbps can be envisioned for a point-to-point link with an energy consumption of 1.9 pJ/bit. Sub-pJ/bit energy consumption is also predicted for aggregated bitrates up to 0.35 Tbps.

We propose a stacked wavelength-division-multiplexed orthogonal-frequency-division-multiplexed passive optical network (WDM-OFDM-PON) system that is capable of transmitting 10-Gb/s per wavelength downstream OFDM signals and directly modulated upstream on-off keying (OOK) signals up to 100 km without any repeater. In this scheme, we use our specially designed electronic controlled liquid tunable optical filter to simultaneously select downstream signals and process upstream signal chirp. By experiment, we demonstrate this bidirectional transmission system and achieve error-free transmission performance over different fiber distances. A power budget of 35.6 dB for 25-km fiber transmission is obtained to support 1 : 512 splitting ratios. Through 100-km fiber transmission, a 34.4-dB optical power budget with a nonrepeater is also achieved. Moreover, the effects of various system parameters such as filter profile and downstream signals' launched power, are also investigated in detail by simulation and experiment for improving system performance.

We not only propose three flexible optical cross-connect (OXC) structures, with the ability of wavelength-division multiplexing (WDM) multicast, but also experimentally demonstrate two WDM multicast schemes based on four-wave mixing in a semiconductor optical amplifier (SOA). One-to-ten WDM multicast of 25-Gb/s QPSK signals is achieved with three pumps, and the power penalties for all signals are less than 1.7 dB. For the first time, dual-channel WDM multicasts are simultaneously realized with only two pumps. One-to-six multicast for one input with the largest power penalty of 1.28 dB is obtained, whereas one-to-three multicast for the other input with the power penalty of 1.27 dB is also realized. The demonstrated schemes can be applied to the proposed OXC structures, according to the different requirements. The effect of bias current on conversion efficiency and optical signal-to-noise ratio is also discussed, and the optimal value is given.

To address key problems of next generation of optical networks and security issues in a simultaneous manner, information theory inspired multidimensional coded-modulation scheme is proposed employing both electrical and optical basis functions. Security is enabled by random selection of orthogonal impulse responses of Sleeping-sequences-based FBGs.