Optical Connections Research Articles

Power-Efficient Single-Sideband Transmission With Clipped Iterative SSBI Cancellation

Distributed data-center networks rely on power and cost-efficient high-speed fiber optical connections over distances up to 80 km which can be densely wavelength-division multiplexed (WDM) in the C-band. Recently, single-sideband (SSB) direct detection (DD) has been considered as an attractive transmission scheme for achieving data rates beyond 100 Gb/s per channel over 80 km. The advantages of SSB DD transmission include its simple transceiver architecture and its capability of electronic dispersion compensation. However, SSB transmissions require a carrier-to-signal power ratio (CSPR) of around 10 dB, even when signal-signal beat interference (SSBI) cancellations are applied. This high CSPR value reduces the power efficiency of the system and limits the total number of WDM channels and accordingly the total system capacity due to power limitation of optical amplifiers. In this article, we propose an iterative SSBI cancellation scheme, which can be effectively applied without digital upsampling at low CSPR values. Using this technique, we have experimentally demonstrated a 30 Gbaud 128 QAM SSB direct detection transmission over 80 km with a low CSPR of 5 dB, showing 4.6 dB performance improvement compared to the Kramers–Kronig scheme operated without digital upsampling.

Fabrication of Low-Cost Molds for Manufacturing of High Precise Micro Parts By Electroforming

Technology push and market pull lead to an intensification of micro molding processes development which have variety of applications such as micro-gears, micro-pumps, micro optical components, connectors, wave-guides, optical gratings and mass production of polymer micro parts and structures with high aspect ratios [1][2]. In these recent years, broad range of microfabrication technologies including, laser ablation, photolithography, lithography, electroplating, and molding (LIGA), chemical etching have been developed [3]. Most of these technologies have been developed for mass production. Manufacturing industry is however more and more facing the problem of producing personalized parts, resulting in low volume production. New technologies to allow economical fabrication of low volume micro-parts become a need.In this work, to address the issue of manufacturing high precise 3D micro-metallic parts for small series, we propose 3D printing of micro-molds followed by electroforming to produce micro 3D metallic parts. Advances in additive manufacturing allow for economical and costly manufacturing of polymer micro-molds with high-resolution to fabricate three-dimensional structures which enables the fabrication of personalized microproducts with virtually any shape. This combination of processes can highly decrease fabrication costs for low volume production.The process starts by printing a mold in Acrylonitrile Butadiene Styrene (ABS). A conductive layer must be included to allow subsequent copper electroforming. Dissolving the ABS part allows in the last step the creation of ultra-light micro-metal parts with a high-quality surface finish and accurate dimensions. Several applications can benefit from a technology able to produce micro dimensional metal parts with thin features like watch industry, medical devices [3] or aerospace and space applications where weight and fraction play key factor.To include the conductive layer into the mold, a two steps process was developed. First step consists in making an ABS substrate with a conductive layer and printing of the ABS mold. Second step is to bond both elements together (Figure, a). The challenge faced is how to bond the substrate with the conductive layer and the upper mold. The developed solution is to thermally bond the substrate’s conductive surface and the upper mold’s surface by apply an appropriate temperature and pressure. Refences [1] L. Weber, W. Ehrfeld, H. Freimuth, M. Lacher, H. Lehr, and B. Pech, “Micromolding: a powerful tool for large-scale production of precise microstructures,” Proc. SPIE - Int. Soc. Opt. Eng., vol. 2879, no. September 1996, pp. 156–167, 1996.[2] T. Katoh, R. Tokuno, Y. Zhang, M. Abe, K. Akita, and M. Akamatsu, “Micro injection molding for mass production using LIGA mold inserts,” Microsyst. Technol., vol. 14, no. 9–11, pp. 1507–1514, 2008.[3] M. Vaezi, H. Seitz, and S. Yang, “A review on 3D micro-additive manufacturing technologies,” Int. J. Adv. Manuf. Technol., vol. 67, no. 5–8, pp. 1721–1754, 2013. Figure 1

Passively Q-switched Yb-doped all-fiber laser based on Ag nanoplates as saturable absorber

Abstract We report on a Q-switched Yb-doped all-fiber laser based on a solution-processed Ag nanoplates saturable absorber. Optical deposition procedure is implemented to transfer the Ag nanoplates onto the fiber core area through the thermal effect. The saturable absorber is sandwiched between two fiber connectors, providing simplicity, flexibility, and easy integration into the laser oscillator. The modulation depth and saturation incident fluence are measured to be ~5.8% and ~106.36 μJ/cm2 at 1-μm region, respectively. Self-started stable Q-switched operation is achieved for a threshold pump power of 180 mW. The repetition rates of the pulse trains range from 66.6 to 184.8 kHz when the pump power scales from 210 to 600 mW. The maximum average output power is 10.77 mW, corresponding to the single-pulse energy of 58.3 nJ and minimum pulse duration of ~1.01 μs. To the best of our knowledge, it is the first time that the Ag nanoplates saturable absorbers are utilized in the 1-μm Yb-doped Q-switched fiber laser.

Hybrid integrated quantum photonic circuits.

Recent developments in chip-based photonic quantum circuits has radically impacted quantum information processing. However, it is challenging for monolithic photonic platforms to meet the stringent demands of most quantum applications. Hybrid platforms combining different photonic technologies in a single functional unit have great potential to overcome the limitations of monolithic photonic circuits. Our review summarizes the progress of hybrid quantum photonics integration, discusses important design considerations including optical connectivity and operation conditions, then highlights several successful realizations of key physical resources for building a quantum-teleporter. We conclude by discussing the roadmap for realizing future advanced large-scale hybrid devices, beyond the solid state platform, which hold great potential for quantum information applications.

Study on multi‐time reflection induced by in‐line fiber connector in engineering applied distributed single‐fiber interferometer sensing system

AbstractIn this article, multi‐time reflection phenomenon induced by fiber connector at the connection point of device module in engineering applied all‐fiber long‐distance distributed vibration sensing system is analyzed and discussed. Despite the application of phase generated carrier (PGC) technology, this multi‐time reflection phenomenon severely degrades the performance of the system. Through theoretical analysis and experiments on the basis of PGC technology, it is found that the influence of multi‐time reflection on the system can be suppressed by selecting appropriate modulation frequency according to the position of the reflection point, and the distortion of the phase retrieved signal is effectively eliminated.

A Novel Repetition Rate Adjustable SBS-Based Q-Switched Fiber Laser

We experimentally demonstrated a novel repetition rate adjustable SBS-based Q-switched fiber laser. An inserted Fabry-Perot interferometer formed by two non-contact end faces of two FC/PC fiber connectors was inserted to help the system stabilize the random output of SBS-based Q-switching. By mechanically fine-tuning the length of the inserted Fabry-Perot interferometer, a linear and continuous repetition rate adjustment under a fixed pump power was achieved. This method paves a new way for the indirect control of repetition rate in SBS-based Q-switched fiber lasers. It is also found out that higher pump power allows wider adjustment range. At 600 mW pumping which is highest pump power of the source, the repetition rate almost tripled from 11.22 kHz to 32.06 kHz only by varying the length of FP cavity in less than 3 μm. In the meantime, the variation of pulse width, output power and single pulse energy were recorded and analyzed under different fixed pump powers. Although the adjusting range of repetition rate is not very wide but the tuning of repetition rate due to such a small length changing is unique and valuable. This original repetition rate control technique has great potential in areas like environment sensing and material detections.

Low-Loss Multimode Glass Waveguides With Beam-Expanded Fiber Connectors Enabling On-Board Optical Links

Ion-exchange glass waveguides are a very promising technology with a balanced trade-off between optical loss, integration density, and fabrication costs. Graded-index multimode waveguides show low propagation loss of only 0.035 dB/cm at wavelength of 1310 nm in glass, compatible with large scale manufacturing. For fiber cable connectivity, expanded beam connectors were used to terminate the waveguides by passive pick-and-place assembly, resulting in a coupling loss of ∼1 dB per interface. Design and fabrication of glass waveguides are studied, and 2-m-long spiral waveguides along with 12 × 12 optical shuffle waveguide layouts made on a 9′′ × 12′′ area glass sheet are demonstrated experimentally.

Generation of Q-switched and mode-locked pulses with Eu2O3 saturable absorber

In this paper, Europium Oxide (Eu2O3) is used as a saturable absorber (SA) to produce Q-switched and mode-locked pulses in an erbium-doped fiber laser (EDFL) cavity. The Eu2O3 was synthesized using casting technique and the resulting Eu2O3 thin film was introduced between two optical fiber ferrule connectors to form a SA. Then the SA was positioned in the EDFL ring cavity. A stable Q-switched operation was achieved by controlling the loss and gain of the cavity. As the pumping power was increased from 84.0 mW to 125.0 mW, the repetition frequency increased from 60.1 kHz to 68.6 kHz and pulse width reduced from 4.5 μs to 3.6 μs respectively. The Q-switched EDFL was operating at the center wavelength of 1568 nm, had a 162 nJ maximum pulse energy and 10.24% slope efficiency. Adding a 100 m SMF in the ring cavity initiated a self-starting mode-locked EDFL and the pulses remained stable within a range of 104.6 to 145.8 mW pump power. At the threshold pump power of 104.6 mW, the mode-locked EDFL operated at a central wavelength of 1565 nm with a repetition rate of 1.8 MHz and a pulse width of 3.51 ps. The results show that Eu2O3 can be deployed as a SA for both Q-switching and mode locking generations.

Advances in Interfacing Optical Fibers to Nanophotonic Waveguides Via Mechanically Compliant Polymer Waveguides

Interfacing standard optical fibers with high index-contrast photonic waveguides remains a substantial challenge restricting the cost-efficiency and scalability of silicon photonic devices. To address this, we have proposed a mechanically compliant polymer interface, formed of a standard fiber connection and a flexible ribbon with lithographically defined polymer waveguides. Self-aligned mechanical assembly and optical mode evolution designs are employed for low cost and large spectral bandwidth. In this paper, we review our progress leading to the full demonstration of this concept with −1.8 dB peak transmission from a plugged-in standard fiber connector to Si wire waveguides. This with 0.7 dB roll-off on a 100 nm bandwidth and all polarization. We present a comprehensive analysis of loss sources and discuss intermediate results, self-alignment accuracy, and reliability.

Signal-to-Noise Ratio of Brillouin Grating Measurement with Micrometer-Resolution Optical Low Coherence Reflectometry.

Signal-dependent speckle-like noise was the dominant noise in a Brillouin grating measurement with micrometer-resolution optical low coherence reflectometry (OLCR). The noise was produced by the interaction of a Stokes signal with beat noise caused by a leaked pump light via square-law detection. The resultant signal-to-noise ratio (SNR) was calculated and found to be proportional to the square root of the dynamic range (DR) defined by the ratio of the Stokes signal magnitude to the variance of the beat noise. The calculation showed that even when we achieved a DR of 20 dB on a logarithmic scale, the SNR value was only 7 on a linear scale and the detected signal tended to fluctuate over ±14% with respect to the mean level. We achieved an SNR of 24 by attenuating the pump light power entering the balanced mixer by 55 dB, and this success enabled us to measure the Brillouin spectrum distributions of mated fiber connectors and a 3-dB fused fiber coupler with a micrometer resolution as examples of OLCR diagnosis.

Status of the Compressed Baryonic Matter experiment at FAIR

The Compressed Baryonic Matter (CBM) experiment will investigate high-energy heavy-ion collisions at the international Facility for Antiproton and Ion Research (FAIR), which is under construction in Darmstadt, Germany. The CBM research program is focused on the exploration of QCD matter at neutron star core densities, such as study of the equation-of-state and the search for phase transitions. Key experimental observables include (multi-) strange (anti-) particles, electron-positron pairs and dimuons, particle correlations and fluctuations, and hyper-nuclei. In order to measure these diagnostic probes multi-differentially with unprecedented precision, the CBM detector and data acquisition systems are designed to run at reaction rates up to 10 MHz. This requires the development of fast and radiation hard detectors and readout electronics for track reconstruction, electron and muon identification, time-of-flight (TOF) determination and event characterization. The data are read-out by ultra-fast, radiation-tolerant, and free-streaming front-end electronics, and then transferred via radiation-hard data aggregation units and high-speed optical connections to a high-performance computing center. A fast and highly parallelized software will perform online track reconstruction, particle identification and event analysis. The components of the CBM experimental setup will be discussed and results of physics performance studies will be presented.

Fiber-optic humidity sensor system for the monitoring and detection of coolant leakage in nuclear power plants

In this study, we developed a fiber-optic humidity sensor (FOHS) system for the monitoring and detection of coolant leakage in nuclear power plants. The FOHS system includes an FOHS, a spectrometer, a halogen white-light source, and a Y-coupler. The FOHS is composed of a humidity-sensing material, a metal tube, a multi-mode plastic optical fiber, and a subminiature version A (SMA) fiber-optic connector. The humidity-sensing material is synthesized from a mixture of polyvinylidene fluoride (PVDF) in dimethyl sulfoxide (DMSO) and hydroxyethyl cellulose (HEC) in distilled water. We measured the optical intensity of the light signals reflected from the FOHS placed inside the humidity chamber with relative humidity (RH) variation from 40 to 95%. We found that the optical intensity of the sensing probe increased linearly with the RH. The reversibility and reproducibility of the FOHS were also evaluated.

Hose-model network virtualization in flexgrid optical networks

Network virtualization, which can flexibly and efficiently embed multiple client networks to a substrate network, is one of the most promising technologies to address the ossification problem of Internet infrastructure. This work focuses on studying the problem of hose-model network virtualization in general topology flexgrid optical networks. A mathematical model for this problem is presented, which integrates hose-model traffic routing and virtual network mapping into a unified integer linear programming (ILP) formulation. Considering the computational difficulty of an ILP algorithm, four heuristic algorithms are presented. They first optimize and allocate link bandwidths to transport hose-model traffic in the virtual network; second, the derived virtual network is mapped in a substrate flexgrid optical network, in which a virtual link is mapped to one or multiple optical connections with or without grooming being allowed. The performance of the mapping success rate and time-average revenue for these algorithms is assessed by extensive simulation.

Long-Term Reliability of Fiber-Optic Current Sensors

We present studies on the long-term reliability of interferometric fiber-optic current sensors (FOCS) for use in electric power transmission systems. Accelerated ageing tests are performed on crucial optical sensor components and a three-phase sensor system is subjected to an extended field trial. The sensor components under test include the sensor’s superluminescent light emitting diode light source, the integrated-optic phase modulator and various passive components such as fiber couplers, fiber polarizers, polarization-maintaining fiber connectors, and fiber coatings. The components are exposed to accelerated ageing conditions for extended periods of time, i.e., temperature cycling (between −25 °C and 65 °C for up to 15000 cycles), constant high temperature at dry conditions (up to 115 °C for up to 20000 h), and damp heat (85 % relative humidity at 85 °C for up to 7900 h). Crucial component parameters such as the source wavelength and polarization extinction ratios are repeatedly measured as a function of temperature at defined intervals during the ageing periods and examined for potential drift of component failures. The field trial is carried out for a three-phase FOCS system integrated into 420 kV double-chamber circuit breakers over a period of more than three years. The sensor signals are compared to the signals of conventional current transformers. In addition, the evolution of various operational parameters such as the light source power is continuously recorded. The results prove a high degree of reliability of modern FOCS systems.

A Routing and Wavelength Assignment Algorithm Based on Two Types of LEO Constellations in Optical Satellite Networks

Research on LEO inter-satellite laser communication based on wavelength division multiplexing inter-satellite links and its routing and wavelength assignment (RWA) technology is an important way to solve the problem of low-latency, high-capacity, high-speed transmission, and low-cost on-orbit real-time routing of free-space optical communications. Since both the transmitting and receiving sides of the inter-satellite communication are high-speed moving satellites, the network topology in the whole inter-satellite communication process is time-varying. Therefore, based on this particularity, we propose the SpacePro constellation and combined the classical NeLS constellation for mathematical modeling, and the network topology and inter-satellite links are predicted and analyzed in their entire cycles. The RWA under the super satellite nodes with computation and storage functions algorithm (SCSA) is proposed and its effect is compared and analyzed in the wavelength resource requirement and connectivity. The results showed that the SCSA algorithm can save up to 50% in wavelength requirements, and the SpacePro constellation can achieve the same network connectivity effect with fewer on-board processors and wavelengths than NeLS. Satellite optical network node connectivity and wavelength demand are a trade-off problem. Studying the RWA problem in this scenario has a very critical reference for how the future satellite optical network performs wavelength usage configuration to help improve the performance of networks.

Study on Soluble Fixed Soft Abrasive Polishing Film Used on Optical Fiber Connector

The end face of an optical fiber connector can be easily contaminated, the curvature radius of the end face can be difficult to guarantee, and the polishing film might not be durable during polishing. To solve these problems, a soluble fixed soft abrasive film polishing method was proposed. Through dyeing and dissolving, tensile strength, and polishing experiments, the influence of the binder and abrasive on polishing film production was studied. The results showed that when the content of each component was 15 wt% epoxy resin, 5 wt% polyacrylic resin, 75 wt% bimodal SiO2, and 5 wt% other additives, the polishing film had superior workpiece polishing quality and durability. After polishing, the end surface of the fiber connector was smooth and clean, the surface morphology of the curved surface was complete, and the surface roughness reached Ra 5 nm.

Delay Aware RSA Algorithm Based on Scheduling of Differentiated Services With Dynamic Virtual Topology Construction

The fast and diversified development of Internet services leads to numerous services with differentiated delay tolerance of optical connections set-up are converging in the optical network. Consequently, the average set-up delay of optical connection is increased, which will inevitably bring pressures to optical networks. To solve this problem, a delay aware routing spectrum assignment (RSA) algorithm based on services scheduling in priority queues with dynamic virtual topology construction (QVT-RSA) is proposed. First, the QVT-RSA algorithm reasonably identifies various different services and arranges them in order according to their priority, waiting time and delay tolerance requirements. Then, software defined networks (SDN) controller with multi-threads technology is adopted to innovatively parallel serve the ordered service requests to reduce the average set-up delay of optical connections, which also offset the induced delay caused by services scheduling. The network resource is accurately shared among multi-threads using the proposed mutual exclusive resource utilization model realized by dynamic virtual topology construction. The continuously coloring and usable virtual topology linkage reconfiguration can provide topology resources for service requests and adapt the dynamic transformation among serving, waiting and new arriving service requests. The shortest-path routing and first fit spectrum assignment (SPFF-RSA) algorithm is used as the baseline algorithm. Furthermore, by combining the SPFF-RSA algorithm and partial strategy of our strategy, the QSPFF-RSA and V-RSA algorithms are proposed as baseline algorithms as described in V-B. The simulation experiment results demonstrate that the average optical connections set-up delay of QVT-RSA algorithm is reduced compared with SPFF-RSA and QSPFF-RSA algorithms, and the blocking probability of QVT-RSA algorithm is reduced compared with SPFF-RSA, QSPFF-RSA and VRSA algorithms. The optical connections set-up success probability within delay tolerance about high, medium and low priority services of QVT-RSA algorithm is higher than that of the SPFF-RSA, QSPFF-RSA and VRSA algorithms.

Layout design fiber optic proximity connector with Expanded Beam technology

This article discusses the layout of a non-contact fiber optic connector for high-power laser radiation delivery systems in the field using Expanded Beam technology (Beam Expander). The technology being implemented, in contrast to contact technology, helps to reduce optical loss from contamination and displacement of the core of optical fibers. The diameter of the beam after passing through the lens becomes 15 times larger than the core of the optical fiber, thereby reducing losses from dust particles at the ends of the optical fibers, which, due to their size, can introduce significant losses. In such connectors, it is proposed to use ball lenses since they are convenient to install and relatively inexpensive. The connector itself is a design with ball lenses, the radiation on which is first converted into a parallel light beam of a larger diameter, and then focuses again on the end of the output fiber. A model was developed, thanks to which the locations of spherical lenses were calculated relative to each other and relative to optical fibers, at which losses would be minimal. The prototype of the connector was assembled from the following components: multimode optical fiber delivery, laser pump diode 975 nm, micromotors, ball lenses and optical power meter. K-8 glass and transparent aluminum oxide Al2O3, traditionally called sapphire in optics, were used as lens materials. The relationship between the transmittance of radiation and the diameter of ball lenses was investigated. Such a connector can be used in laser delivery systems, such as explosive squibs in the aerospace and mining industries.

基于ZEMAX的扩束型光纤连接器对准误差分析

基于ZEMAX的扩束型光纤连接器对准误差分析

Hesitant-Fuzzy Sets-Based Computational Approach for Evaluating the Survivability Impact of Multi-Fiber WDM Networks: Kingdom of Saudi Arabia Perspective

Saudi Arabia's Information and Communication Technology (ICT) industry is undergoing different stages of modernization. Over the last few decades, the ICT industry has been experiencing rapid growth. The understanding of disruption as well as fluctuation in channel capacity gives an idea about the optical fiber network. A primary necessity for the optical communication industry is to achieve the desired effect of survival and growth. Scientific researchers are trying to achieve the objective of optimum optical network services survivability. The proposed paper attempts to describe and analyze the effect of multiplexing in multi-fiber wavelength. To analyze and assess the effect in more scientific and systematic manner, the authors have used a multi criteria decision making (MCDM) approach named the hesitant fuzzy analytical hierarchy process as well as TOPSIS methods in this paper. With the help of these adopted MCDM approaches, the authors have assessed the surviving strength and capacity of multiplexing. For this empirical model, five features and two levels of alternatives were chosen. A combination of two principal alternatives was the first level, and the second level had its five based alternatives. For this analysis, the unified symmetrical decision making strategy of Hesitant-Fuzzy AHP with Hesitant-Fuzzy TOPSIS was established. The findings obtained on survivability in this research will be a point of reference for developing the next level wavelength division multiplexing in optical transmission network communication. In the sense of producing gigabits and terabits per second, this inquiry will further reinforce optical fiber connectivity.