Optical Connections Research Articles

Power-aware high-capacity elastic optical networks

The power consumption of telecommunication equipment has been identified as a relevant contributor to global energy consumption. In fact, new-generation optical transponders employ power-intensive electronic application-specific integrated circuits (ASICs) for digital signal processing (DSP). DSP design has traditionally prioritized meeting transmission requirements over power consumption optimization. In general, the evolutions of transmission techniques and network design have always been mainly driven by traffic increase; in this context, in order to operate network resources more efficiently, margin reduction has been investigated in the past few years. Indeed, traditionally, high physical layer margins are used to ensure reliability over an extended period, resulting in overprovisioning the optical connections for both physical layer conditions and capacity. On the other hand, super-channels have emerged as a suitable solution for accommodating the continuous traffic growth. However, power consumption has not been deeply considered in the optimization of super-channel transmission. This paper first investigates the power efficiency of super-channels operated with designed and reduced margins. Low-margin operation is enabled by adapting sub-carrier spacing and filter bandwidth. Power-aware super-channel optimization is then experimentally demonstrated leveraging a 600 Gbit/s transponder in the SDN-controlled elastic optical network (EON). The results have identified a trade-off between power consumption and spectrum efficiency. Furthermore, the ongoing bandwidth demand has motivated the investigation of multi-band (MB) transmission for scaling the capacity of the existing infrastructures. However, novel networking devices (e.g., optical amplifiers operating beyond the C- and L-bands) will affect the overall power consumption. In this context, experimental power analysis of a thulium doped fiber amplifier (TDFA) is performed based on the traffic load and corresponding configuration. The results show that TDFA power consumption varies with configuration and increases with output power.

Spatial Mode Division Multiplexing of Free-Space Optical Communications Using a Pair of Multiplane Light Converters and a Micromirror Array for Turbulence Emulation

Multi-plane light converters (MPLC) are a means of deconstructing a wavefront into constituent modes that are focused at specific spatial locations, and the reverse—that specific inputs result in controlled modal output. We have used a pair of MPLCs with 21 Hermite–Gaussian modes to represent a free-space optical connection. The effects of strong atmospheric turbulence (Cn2 = 10−13 m−2/3) are emulated using a micromirror array producing a time sequence of aberrating frames. The modal crosstalk between transmitter and receiver modes induced by the turbulence is presented by measuring the intensity in receiver channels for the same turbulence. Six receiver modes are used for optical communication channels with a rate of 137 Gbits/s displaying the benefits of single input multiple output (SIMO) operation for overcoming the deleterious effects of turbulence.

Time error accumulation in a hierarchical time and clock distribution network with deterministic optical links

Accurate clock and time distribution is a key requirement for self-triggered streaming data acquisition in the CBM experiment. This distribution is handled by the Timing and Fast Control (TFC) system by clock forwarding and broadcasting the common time over latency-deterministic optical links in a hierarchical FPGA network. The point-to-point optical connections are served by the latency-optimized GBT-FPGA core, which has been developed at CERN. In the presented work, the performance of GBT-FPGA links for time and clock distribution in a scaled TFC system with multiple hops and endpoints has been investigated.

Context-Based e2e Autonomous Operation in B5G Networks.

The research and innovation related to fifth-generation (5G) networks that has been carried out in recent years has decided on the fundamentals of the smart slice in radio access networks (RANs), as well as the autonomous fixed network operation. One of the most challenging objectives of beyond 5G (B5G) and sixth-generation (6G) networks is the deployment of mechanisms that enable smart end-to-end (e2e) network operation, which is required for the achievement of the stringent service requirements of the envisioned use cases to be supported in the short term. Therefore, smart actions, such as dynamic capacity allocation, flexible functional split, and dynamic slice management need to be performed in tight coordination with the autonomous capacity management of the fixed transport network infrastructure. Otherwise, the benefits of smart slice operation (i.e., cost and energy savings while ensuring per-slice service requirements) might be cancelled due to uncoordinated autonomous fixed network operation. Notably, the transport network in charge of supporting slices from the user equipment (UE) to the core expands across access and metro fixed networks. The required coordination needs to be performed while keeping the privacy of the radio and fixed network domains, which is important in multi-tenant scenarios where both network segments are managed by different operators. In this paper, we propose a novel approach that explores the concept of context-aware network operation, where the slice control anticipates the aggregated and anonymized information of the expected slice operation that is sent to the fixed network orchestrator in an asynchronous way. The context is then used as the input for the artificial intelligence (AI)-based models used by the fixed network control for the predictive capacity management of optical connections in support of RAN slices. This context-aware network operation aims at enabling accurate and reliable autonomous fixed network operation under extremely dynamic traffic originated by smart RAN operation. The exhaustive numerical results show that slice context availability improves the benchmarking fixed network predictive methods (90% reduction in prediction maximum error) remarkably in the foreseen B5G scenarios, for both access and metro segments and in heterogeneous service demand scenarios. Moreover, context-aware network operation enables robust and efficient operation of optical networks in support of dense RAN cells (>32 base stations per cell), while the benchmarking methods fail to guarantee different operational objectives.

Across-dimensional optical constellation de-aggregations from QAMs to PAMs in optical transparent networks

In this paper, an across-dimensional optical constellation de-aggregation scheme is proposed and verified. This de-aggregation scheme builds flexible optical connections between core and edge networks and fills the lack of the conversions between quadrature amplitude modulation (QAM) and pulse amplitude modulation (PAM) formats. 10G Baud quadrature phase shift keying/9QAM/16QAM-to-2×on off keying (OOK)/PAM3/PAM4 constellation de-aggregations are achieved. The enabled constellation manipulations contain polarization-assisted quadrature de-multiplexing and bi-directional vector moving. The key research status of QAM/PAM de-aggregations and adopted theoretical derivations are analyzed and expressed in detail. The signal spectrum, constellations, eye diagrams, transfer characteristics curves, error vector magnitudes and bit error ratios (BERs) during the de-aggregation process are calculated to measure the system performances. With the input optical signal-to-noise ratio (OSNR) of 10 dB/15 dB/20 dB, the de-aggregated OOK/PAM3/PAM4 signals show the receiver OSNR of 19.1 dB/21.9 dB/31.2 dB, respectively, at the BER of 10−3. The proposed scheme presents excellent format scalability and has potential applications in flexible all-optical connections, across-dimensional optical transmissions, and optical transparent networks.

Photonic Gateway accommodating all types of wavelength paths for digital-coherent and IM-DD user terminals in all-photonic metro-access converged networks

In access and metro networks, there is increasing demand for guaranteed wide-bandwidth and stringent/deterministic end-to-end latency characteristics. Converging these networks by expanding dense wavelength-division-multiplexed metro networks to access areas is a promising approach to satisfy this demand. An All-Photonics Metro-Access Converged Network (APN) dynamically and flexibly provides a wavelength connection between any two points including user premises. This evolution in network architecture presents some technical challenges. First, from the access-node architecture viewpoint, conventional reconfigurable optical add/drop multiplexers (ROADMs) do not have functions for remote and in-channel user-terminal (UT) control or turn-back connection within the access area. Therefore, the APN cannot be achieved by simply adopting ROADMs as access nodes, which are defined as Photonic Gateways. Remote and in-channel UT controls are required to control the endpoints of a wavelength path beyond the carrier control-plane network. These types of control should be independent of the protocol and modulation/detection method for the main signal. In addition, the Photonic Gateway must flexibly and efficiently support a new type of wavelength path, specifically a turn-back connection within the access area, due to metro/access convergence. Second, from the viewpoint of the process for dynamic wavelength-path provisioning, the APN controller should autonomously discover physical connectivity between a UT and the Photonic Gateway connected via field access fibers. This paper proposes a novel Photonic Gateway architecture that flexibly and scalably provides various UTs with direct optical connections including turn-back configurations. This paper also proposes a method that autonomously recognizes physical connections between newly connected UTs and the Photonic Gateway. The proposed architecture and method are experimentally verified based on all types of wavelength-path provisioning that take at most 72 s using Photonic Gateway prototypes, 100-Gb/s digital-coherent UTs, and 10-Gb/s intensity-modulation direct-detection UTs. All types of wavelength paths that are provided over the APN architecture are considered including a turn-back connection between two UTs within the same access area and connections between two UTs that traverse the metro area with or without optical/electrical conversion.

A research on optical wireless sensor connections using non-orthogonal multiple access techniques

This research endeavor delves into the utilization of non-orthogonal multiple access (NOMA) techniques within the context of optical wireless sensor networks (OWSNs). The study entails an exploration of the viability of integrating NOMA into OWSNs and introduces a novel architectural framework that amalgamates successive interference cancellation (SIC) and superposition coding methodologies. This amalgamation aims to enhance the overall performance and spectral efficiency of the network. The investigation meticulously assesses the performance of the proposed architecture, employing diverse metrics such as bit error rate (BER), outage probability, and environmental impact. Empirical results underscore the commendable precision of the NOMA-based architecture when juxtaposed with conventional orthogonal multiple access (OMA) approaches. This distinction is particularly pronounced in scenarios involving a substantial number of sensor nodes. Furthermore, the research undertakes a comprehensive scrutiny of varying system parameters, such as user densities and power allocation factors, to gauge their influence on network accuracy. The discerned outcomes elucidate NOMA’s capacity to augment the operational efficacy of optical wireless sensor connections. The proposed architectural paradigm thus emerges as a promising avenue for optimizing resource allocation and utilization within OWSNs, imparting newfound potential to a spectrum of applications spanning industrial automation, environmental monitoring, and smart city implementations.

Experimental study of a temperature measurement system for an overhead power line using sensors based on TFBG

This article presents the use of an inclined fiber sensor Bragg grid to control the extension of wires in overhead lines. An aspect of the technological novelty of the project is the development of an innovative optoelectronic system for monitoring and diagnosing the condition of building structures based on a combination of conventional Bragg gratings. The lighting power sensor is installed directly on the controlled transmission of the power line in the form of fittings with a copper plate. A photosensitive multimode optical fiber is attached to the copper plate, at the end of which an inclined fiber Bragg grating is fixed, connected to a multimode optical fiber using a fiber-optic connector through an optical connector. An ultraviolet excimer laser and a light power detector are connected to a fiber-optic connector. The study showed that by selecting the appropriate mechanical parameters of the extension transformer, taking into account the optical parameters of the sensor, and using a special filter, the optical-mechanical system can be configured in the required range to control the sagging of the overhead line wire. During measurements to simulate the operation of a power line wire, the temperature was forced to vary in the range of 10-60°C. This led to the lengthening of the test wire from 38.987 m to 49.275 m; the error was within 4%. The deflection range depends on the distance between the supports, the type of wire, and its actual length in the span, which actually determines the deflection.

Bit Error Rate Performance in CDMA Free Space Optical Links with SIK Receiver under Fog Conditions

This article presents a novel analytical method for evaluating fog's impact on Bit Error Rate (BER) in an Optical Code Division Multiple Access (OCDMA) Free Space Optical (FSO) connection. The investigation employs an optical encoder and direct detection receiver employing a balanced photo detector with Sequence Inverse Keying (SIK) to explore fog effects. By scrutinizing multi-access interference (MAI) current and signal current values at the SIK receiver's output under varied fog conditions, we deduce BER expressions for diverse scenarios. These encompass different fog thickness levels, code lengths, simultaneous users, and system parameters. The results reveal substantial OCDMA degradation due to fog thickness and users. Also, the system incurs a marked power penalty at a specific BER, especially with higher fog and user density. However, we identify a potential solution: increasing code length, effectively mitigating fog-induced performance decline.

Design for Hollow-Core fiber connector

This paper describes a newly developed butt joint type hollow-core fiber connector with protected fiber ends. It can typically realize nearly 0.5-dB insertion and 45-dB return loss without physical contact. It has been confirmed that the HCF connector is suitable for actual use because it maintains stable connection characteristics in mating cycles, and it can be cleaned with an ordinary connector cleaner.

Ferrule Endface Dimension Optimization for Standard Outer Diameter 4-Core Fiber Connector

Ferrule Endface Dimension Optimization for Standard Outer Diameter 4-Core Fiber Connector

Highly Sensitive Temperature Sensor Based on Vernier Effect Using a Sturdy Double-cavity Fiber Fabry-Perot Interferometer.

Temperature measuring is a daily procedure carried out worldwide in practically all environments of human activity, but it takes particular relevance in industrial, scientific, medical, and food processing and production areas. The characteristics and performance of the temperature sensors required for such a large universe of applications have opened the opportunity for a comprehensive range of technologies and architectures capable of fulfilling the sensitivity, resolution, dynamic range, and response time demanded. In this work, a highly sensitive fiber optic temperature sensor based on a double-cavity Fabry-Perot interferometer (DCFPI) is proposed and demonstrated. Taking advantage of the Vernier effect, we demonstrate that it is possible to improve the temperature sensitivity exhibited by the polymer-capped fiber Fabry-Perot interferometer (PCFPI) up to 39.8 nm/°C. The DCFPI is sturdy, reconfigured, and simple to fabricate, consisting of a semi-spherical polymer cap added to the surface of the ferrule of a commercial single-mode fiber connector (SMF FC/PC) placed in front of a mirror at a proper distance. The length of the air cavity (Lair) was adjusted to equal the thickness of the polymer cap (Lpol) plus a distance δ to generate the most convenient Vernier effect spectrum. The DCFPI was packaged in a machined, movable mount that allows the adjustment of the air cavity length easily but also protects the polymer cap and simplifies the manipulation of the sensor head.

Development of a Handheld Optical Fusion Splicer with a Wing Sleeve Optical Connector

FTTH (Fibre to the Home) uses a fusion splice field-assembled optical connector. The fusion splice field-assembled optical connector is connected and assembled using a generic fibre fusion splicer. However, general purpose fusion splicers make the device difficult to operate in the installation field because the fusion splicer is too large and heavy to handle. As a result, the fibre optic splice often breaks during the optical connector assembly process. This makes it difficult to apply fusion-spliced optical connectors in the FTTH field. To solve this problem, this paper proposes a fusion splicer for FTTH that can perform fusion splicing using a wing-type sleeve optical connector. The proposed fusion splicer, with a connection module with a lifting/lowering function, is implemented to connect and protect the wing-type sleeve field-assembled optical connector. In addition, by eliminating the tube heater used as a connection protection method in the existing fusion splicer, the power module is reduced. The developed fusion splicer was evaluated for assembly reliability through splice loss measurements and a comparison of assembling time with the existing fusion splicer.

Optical Fiber Connector Technology

Various optical fiber connectors have been developed during the 40 years since optical fiber communications systems were first put into practical use. This paper describes the key technologies for optical connectors and recent technical issues.

Three Blind Moles: Molecular Evolutionary Insights on the Tempo and Mode of Convergent Eye Degeneration in Notoryctes typhlops (Southern Marsupial Mole) and Two Chrysochlorids (Golden Moles).

Golden moles (Chrysochloridae) and marsupial moles (Notoryctidae) are textbook examples of convergent evolution. Both taxa are highly adapted to subterranean lifestyles and have powerful limbs for digging through the soil/sand, ears that are adapted for low-frequency hearing, vestigial eyes that are covered by skin and fur, and the absence of optic nerve connections between the eyes and the brain. The eyes of marsupial moles also lack a lens as well as retinal rods and cones. Two hypotheses have been proposed to account for the greater degeneracy of the eyes of marsupial moles than golden moles. First, marsupial moles may have had more time to adapt to their underground habitat than other moles. Second, the eyes of marsupial moles may have been rapidly and recently vestigialized to (1) reduce the injurious effects of sand getting into the eyes and (2) accommodate the enlargement of lacrimal glands that keep the nasal cavity moist and prevent the entry of sand into the nasal passages during burrowing. Here, we employ molecular evolutionary methods on DNA sequences for 38 eye genes, most of which are eye-specific, to investigate the timing of relaxed selection (=neutral evolution) for different groups of eye-specific genes that serve as proxies for distinct functional components of the eye (rod phototransduction, cone phototransduction, lens/cornea). Our taxon sampling included 12 afrothere species, of which two are golden moles (Amblysomus hottentotus, Chrysochloris asiatica), and 28 marsupial species including two individuals of the southern marsupial mole (Notoryctes typhlops). Most of the sequences were mined from databases, but we also provide new genome data for A. hottentotus and one of the two N. typhlops individuals. Even though the eyes of golden moles are less degenerate than the eyes of marsupial moles, there are more inactivating mutations (e.g., frameshift indels, premature stop codons) in their cone phototransduction and lens/cornea genes than in orthologous genes of the marsupial mole. We estimate that cone phototransduction recovery genes were inactivated first in each group, followed by lens/cornea genes and then cone phototransduction activation genes. All three groups of genes were inactivated earlier in golden moles than in marsupial moles. For the latter, we estimate that lens/cornea genes were inactivated ~17.8 million years ago (MYA) when stem notoryctids were burrowing in the soft soils of Australian rainforests. Selection on phototransduction activation genes was relaxed much later (5.38 MYA), during the early stages of Australia's aridification that produced coastal sand plains and eventually sand dunes. Unlike cone phototransduction activation genes, rod phototransduction activation genes are intact in both golden moles and one of the two individuals of N. typhlops. A second marsupial mole individual has just a single inactivating mutation in one of the rod phototransduction activation genes (PDE6B). One explanation for this result is that some rod phototransduction activation genes are pleiotropic and are expressed in extraocular tissues, possibly in conjunction with sperm thermotaxis.

Impact of Optical Connectors on QKD Transmission

ABSTRACT This paper describes the effect of different optical connector polishing techniques on the quantum channel of a quantum key distribution (QKD) C l a v i s 3 system. First, the basic differences among these types of connector polishing are briefly described. Second, the paper focuses on the design of a simple optical route to measure the effect of APC/UPC (angled physical contact/ultra physical contact) connectors on the quantum channel functionality, which is attributed to the slightly different characteristics of the two types of connectors. However, both types of connectors are commonly employed in real networks. For this reason, two series of measurements are made, one measurement for APC connectors and one measurement for UPC connectors. In each series, the number of connectors is gradually increased by up to 12 connectors per route for a given type. Finally, the results of the measurements, which mainly comprise changes in the three main parameters, are presented. In particular, the key rate, interferometric visibility and QBER (quantum bit error rate) were monitored.

Passively Q-switching an all polarization-maintaining erbium-doped fiber laser with a rhenium disulfide (ReS2) saturable absorber

This study demonstrates a linearly polarized Er-doped fiber laser system featuring an all-polarization-maintaining (all-PM) architecture. Short pulses were generated by Q-switching operation based on drop-casting rhenium disulfide (ReS2) saturable absorber (SA) onto a fiber connector placed inside the laser cavity. The Q-switching operation of the laser was able to self-start at a low (23 mW) threshold power of the pump and without the need to use a polarization controller. The proposed laser was able to produce stable pulses with a center wavelength and 3-dB bandwidth of 1558.4 nm and 0.13 nm, respectively. The shortest pulse duration measured (2.8 μs) was achieved at a repetition rate of 37.6 kHz while the highest average output power and pulse energy were 2.2 mW and 76.5 nJ, respectively. Furthermore, as the cavity of the laser was designed to be all-PM the laser that it produced was linearly polarized and had a degree of polarization (DOP) at the level of 94.5 % and 40 dB polarization extinction ratio (PER). Therefore, the proposed laser is a suitable light source for optical applications in environments that are complex.

Risk management analysis of public street lighting (SMART PJU) as Quick win smart environment of Semarang City

Successful implementation of a program is the goal of program design. However, currently, many programs fail to be implemented due to the failure of efforts to prevent the occurrence of failure factors. Especially in the era of digital governance such as today, the planning of various smart city programs has a large potential risk of implementation failure. The Semarang City of Smart PJU, for example, the implementation of the use of analytics-based SMART PJU requires long and careful preparation. Not only management preparation but risk management is also needed for the program. This research aims to analyze the map of potential risks in the Semarang City SMART PJU of IoT program along with analyzing how the risk management of the program. This research is based on qualitative research with primary and secondary data collection techniques. Primary data collection by interviewing related informants purposively, then the data is analyzed based on qualitative analysis. The findings of this research are that the highest level of risk occurs in the shortage of human resources and SMART PJU operators because there are no human resources who are data analytic experts and Artificial Intelligence experts. Other high risks are database errors / down; SMART PJU devices using old technology; long loading dashboards; and no Fiber Optic connection in internet management.

Hybrid tree-and-multiple-ring radio-over-fiber transmission system for a 5G network in metropolitan areas

What we believe to be a novel radio-over-fiber (RoF) transmission system with a hybrid tree-and-multiple-ring network structure is developed and experimentally demonstrated to support broadband wireless signal transmission among the central office (CO) and densely distributed 5G base stations (BS) in urban areas. With the assistance of an advanced network structure and a unique single-line bidirectional optical add/drop multiplexer (SBOADM), the transmission system can utilize a hybrid tree-and-ring-topology fiber network to simultaneously support multiple 5G BS-Groups constructed as sub-ring-networks. Furthermore, the system manager is able to simultaneously utilize wavelength/time division multiplexing techniques to support the connected BSs and to dynamically embed extra sub-ring-networks to the main-ring-network or extra BSs to the sub-ring-network by using the RoF transmission system. Needing no backup fiber link, the transmission system enjoys intrinsic robust resilience against fiber link failures. Experimental results proved that the proposed RoF transmission system enables prompt recovery of interrupted optical fiber connection and guarantees the expected quality of service (QoS) by adjusting a few preinstalled optical switches when fiber link failure happens in the main-ring-network, in each sub-ring-network, or even in both of the above scenarios. The induced power penalty for maintaining unchanged bit error rate performance is less than 2 dB. In sum, the proposed transmission system proves to be a great network architecture suitable for supporting 5G signal transmission between the CO and BSs in an urban area due to the dynamically extensible network size and the well-protected transmission that ensures the QoS by simple operation.

Ultrafast laser processing of glass waveguide substrates for multi-fiber connectivity in co-packaged optics

High bandwidth demanding applications such as high-performance computing and hyperscale datacenters are drivers for co-packaged optics, which aims to bring optical signals as close as possible to the electrical computing chips by integrating the electro-optic transceivers and ASICs on the same package substrate. These next-generation switches require advanced fiber-to-chip connectivity and novel packaging concepts to enable sufficient power and cost savings. As such, low-loss, high bandwidth, and high fiber-counts are required at the photonic chip interface. In this work, these challenges are addressed by enabling the multi-fiber push-on (MPO) interface at the edge of integrated glass waveguide substrates and thus leverages the existing fiber connector eco-system. An ultrafast laser process is used to singulate glass wafers into individual photonic chips leaving optical-quality end-facets with <1 μm flatness over the 6.5 mm wide connector region thereby directly enabling low-loss fiber-to-chip edge-coupling. To overcome the high-costs and complex photonic packaging associated with active alignment of the fiber connectors to the glass waveguide interfaces, ultrafast laser-ablated features are accurately positioned on the glass substrate to enable self-alignment of the MPO connector guide-pins resulting in a passive alignment approach. Subsequent mating and de-mating of the MPO connector to the glass waveguide interface yields on average a 0.19 dB increase in the coupling loss compared to using active alignment.