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Preview: Lightwave Technology, Journal of - new TOC

Journal of Lightwave Technology - new TOC



TOC Alert for Publication# 50



 



Front Cover

Dec.15, 2017

Presents the front cover for this issue of the publication.



Journal of Lightwave Technology

Dec.15, 2017

Provides a listing of current staff, committee members and society officers.



Table of Contents

Dec.15, 2017

Presents the table of contents for this issue of the periodical.



Nanowaveguide Enhanced Photothermal Interferometry Spectroscopy

Dec.15, 15 2017

We report a new optical nanowaveguide enhanced photothermal (PT) interferometry spectroscopy method for trace molecule detection. Absorption of pump evanescent field of an optical nanowaveguide heats up the trace molecules surrounding the waveguide, causing the temperature of waveguide to rise via thermal conduction and modulating the refractive index and dimension of the nanowaveguide. The phase of a probe beam propagating through the same nanowaveguide is then modulated and can be detected with optic fiber interferometry. Numerical simulation with silica, cyclic transparent optical polymer, and silicon nanowaveguides with proper dimensions can achieve PT index modulation of 10 to over 8000 times that of the commercial HC-1550-02 photonic bandgap fiber. Experiments with 12-mm-long, 800-nm-diamter silica nanofiber demonstrated a lower detection limit of 600 parts per billion (ppb) acetylene at ambient conditions.



High-Sensitivity Fabry-Perot Interferometric Acoustic Sensor for Low-Frequency Acoustic Pressure Detections

Dec.15, 15 2017

We demonstrate a fiber-optic Fabry-Perot acoustic sensor based on a Parylene-C diaphragm of 500 nm in thickness. The excellent diaphragm forming ability and good adhesion of Parylene-C make the sensor fabricate up to 9 mm in diameter. Acoustic testing demonstrates a high dynamic pressure sensitivity of 2239 nm/Pa and a noise limited equivalent acoustic signal level of 22.1 μPa/Hz1/2 at the frequency of 20 Hz. The frequency response exhibits an obvious peak at the frequency of 13 Hz. The sensor can be used for low-frequency acoustic pressure detections, which is necessary in surveillance and security systems.



Er-Doped Mode-Locked Fiber Laser With a Hybrid Structure of a Step-Index–Graded-Index Multimode Fiber as the Saturable Absorber

Dec.15, 15 2017

A mode-locked all-fiber laser based on the nonlinear multimode interference (NL-MMI) effect of the graded-index multimode fiber (GIMF) is proposed and demonstrated. The saturable absorber (SA) used in the laser consists of a step-index multimode fiber (SIMF) connected by a GIMF. Compared with the theoretically proposed SMF–GIMF–SMF structure, the introduction of the SIMF eliminates the restriction on the length of the GIMF and provides a more flexible method of making an SA based on the NL-MMI. Through bending the device to a certain state, the modulation depth of the SA was measured to be 3.16%. The mode-locked laser output pulses have the pulsewidth of ∼446 fs, the bandwidth of 4.48 nm, and the fundamental repetition rate of 11.73 MHz. This versatility and simplicity of the SA device combined with the possibility of scaling the pulse energy in the large-mode-area double-clad fiber laser make it highly attractive in ultrafast photonics.



Numerical Investigation of SOA Nonlinear Impairments for Coherent Transmission Systems Based on SOA Amplification

Dec.15, 15 2017

For the purpose of revisiting the semiconductor optical amplifier (SOA) ability for large-band amplification in the context of wavelength division multiplexed (WDM) coherent systems, we numerically investigate nonlinear impairments brought by SOA for polarization multiplexed quadrature phase-shift keying and polarization multiplexed 16-quadrature amplitude modulation terrestrial transmissions. In order to provide a deep understanding of these impairments, we perform a step-by-step approach by assessing the transmission performance of a sole SOA cascade and an SOA-amplified transmission system using linear and then nonlinear fiber. For the same purposes, we also study these impairments for a single-channel transmission even though the final goal is to design a WDM SOA-amplified system with a larger bandwidth than the EDFA-based systems. We show some interesting results on the span-after-span accumulation of SOA nonlinear impairments, as it has been done similarly for the fiber nonlinearities, in the context of dispersion managed or unmanaged coherent systems. Design guidelines of both SOAs for amplification purposes and SOA-amplified transmission systems are derived from this investigation. Finally, we point out promising results for SOA-based transmissions, for particular system configurations that follow these guidelines.



Intermodal Four-Wave Mixing and Parametric Amplification in Kilometer-Long Multimode Fibers

Dec.15, 15 2017

We theoretically and numerically investigate intermodal four-wave mixing in kilometer-long fibers, where random birefringence fluctuations are present along the fiber length. We identify several distinct  regimes that depend on the relative magnitude between the length scale of the random fluctuations and the beat lengths  of the interacting quasi-degenerate modes. In addition, we analyze the impact of mode dispersion and we  demonstrate that random variations of the core radius, which are typically encountered during the drawing stage of the fiber, can represent the major source of bandwidth impairment. These results set a boundary on the limits of validity of the classical Manakov model and may be useful for the design of multimode parametric amplifiers and wavelength converters, as well as for the analysis of nonlinear impairments in long-haul spatial division multiplexed transmission.



48 GHz High-Performance Ge-on-SOI Photodetector With Zero-Bias 40 Gbps Grown by Selective Epitaxial Growth

Dec.15, 15 2017

High-performance normal-incidence p-i-n Ge photodetectors for 1550 and 1310 nm were grown by selective epitaxial growth on SOI substrate with in situ thermal annealing and surface Si passivation. Bulk leakage current density and surface leakage density as low as 3.4 mA/cm2 and 0.4 μA/cm are achieved under –1 V, respectively. Resonance optical responsivity at 1550 and 1310 nm are 0.27 and 0.59 A/W under zero-bias, respectively. A 3-dB bandwidth as high as 48 GHz is obtained at –3 V. Clear open eye diagrams at 40 Gbps are demonstrated under zero-bias at 1550 nm.



Brillouin Optical Correlation Domain Analysis Enhanced by Time-Domain Data Processing for Concurrent Interrogation of Multiple Sensing Points

Dec.15, 15 2017

We propose and experimentally demonstrate a Brillouin optical correlation domain analysis system adopting time-domain data processing and differential measurement for simultaneous interrogation of multiple sensing points. Continuous probe and pulsed pump waves are simultaneously frequency-modulated by a MHz-order sinusoidal RF wave so that multiple correlation peaks are sequentially generated according to the propagation of the pump along a fiber under test (FUT). The Brillouin gain spectrum of each correlation peak is obtained and interrogated by moving window averaging of the probe wave with a span of the period of the RF modulation, leading to the simultaneous monitoring of the multiple sensing points. In experiments, 148 correlation peaks are concurrently interrogated with a spatial resolution less than 3 cm along a 1530 m FUT.



Effect of Dopant Diffusion on the Long-Term Stability of Fabry–Pérot Optical Fiber Sensors

Dec.15, 15 2017

We present a research to determine the long-term stability of intrinsic Fabry–Pérot (F–P) optical fiber sensors in high-temperature environments. In-fiber sensors were created in 125 μm diameter single mode fiber (Corning SMF28 Ultra) and a 125 μm diameter PCF ESM-12B pure SiO2 fiber spliced to a SMF28 fiber with a low reflectivity Cr layer at the interface. The outcome is a low finesse optical cavity either formed by a short length of Ge doped SMF fiber, or a short length of pure and undoped SiO2 core PCF fiber. We demonstrate the manufacturing technique required for these intrinsic F–P sensors as well as the stability of their optical characteristics at temperatures up to the range of 850 °C to 1050 °C. We report on the effect of annealing on stability after exposing sensors to temperatures of 1000 °C above nominal working temperatures. In the temperature range above 900 °C we observe increasing levels of nonreproducible drift characteristics. Stability is demonstrated up to 1000 °C. After extended exposure of sensors to high temperatures we observe deviations from the initial smooth second-order response of phase versus temperature, which has been attributed to a change in core diameter in the fiber leading to the sensor at the distal end due to Ge diffusion at the high temperatures. The down lead is exposed to over a length of 17 cm. The dopant diffusion of an SMF28 ultra fiber has been studied using Energy Dispersive X-rays analysis (SEM/EDX), to measure the radial distribution of Ge concentration before and after being heated for a period of 100 days.



Secure MIMO Visible Light Communication System Based on User's Location and Encryption

Dec.15, 15 2017

Visible light communication systems are rapidly growing research areas with wide applications ranging from illumination and data communication. To achieve high data rates in such systems, a number of techniques have been employed such as equalization of transmission signals, deployment of complex data modulation and the use of multiple input multiple output (MIMO) systems. However, security in wireless telecommunication systems is a common concern. This paper proposes a secure MIMO-VLC system that relies on the position of the user by incorporating a new modified version of the Rivest–Shamir–Adleman (RSA) technique for encrypting the transmitted data in the media access control MAC layer. The performance of the positioning method is evaluated showing a positioning accuracy of less than 5 cm for a signal-to-noise ratio of 15 dB. Furthermore, the ability of the proposed system to control the size of the encrypted cell, depending on the application environment, is demonstrated.



Data-Oriented Task Scheduling in Fixed- and Flexible-Grid Multilayer Inter-DC Optical Networks: A Comparison Study

Dec.15, 15 2017

It is known that in multilayer interdatacenter optical networks (ML-IDCONs), network services can generate numerous data-oriented tasks (DoTs) that require not only inter-datacenter (DC) data transfers but also data processing in the DCs. In this paper, we perform a comparison study on the scheduling of DoTs (i.e., setting up lightpaths on fiber links for inter-DC data transfers and scheduling DoT buffering/processing in DCs) in fixed- and flexible-grid ML-IDCONs. We propose a DoT scheduling algorithm that can work well for both types of networks. Specifically, for each DoT, the algorithm first tries to serve it using the residual bandwidth in the IP layer. This is achieved by expanding the time-expanded network approach and transforming the store-and-forward assisted DoT scheduling problem into a minimum-cost maximum-flow (MCMF) problem. Then, by solving the MCMF problem, we find the way to maximize the data transfer throughput and minimize the total dc storage usage simultaneously. Next, if the obtained data transfer throughput is not sufficient for the DoT, the algorithm tries to build lightpath segments for it based on the branch and bound scenario. Extensive simulations are conducted to evaluate the proposed algorithm's performance in fixed- and flexible-grid ML-IDCONs, and also compare it with three benchmarks. Simulation results indicate that for DoT scheduling, the flexible-grid ML-IDCON can outperform fixed-grid ones in terms of the blocking probability, energy consumption of transponders, and usage of dc storage, and our algorithm achieves lower blocking probability than the benchmarks with comparable or higher time-efficiency.



Cascading Second-Order Microring Resonators for a Box-Like Filter Response

Dec.15, 15 2017

We demonstrate an optical filter using multistage of second-order microring resonators (2nd-order MRRs) for a box-like filter response. All stages have identical structure parameters elaborately designed to obtain a flat-top spectrum. The maximally flat condition is deduced in consideration of loss and compared with those reported in literature. We present the insertion loss, extinction ratio, bandwidth, and roll-off rate of the maximally flat response. We find that for the flat response of a 2nd-order MRR, the product of bandwidth and roll-off rate is constant. We compare the cascading 2nd-order MRRs with single-stage high-order filters with the same number of ring cavities. We find that the cascading structure has comparable performances in the aspects of insertion loss and roll-off rate for small radius. This cascading structure relaxes the fabrication tolerance and mitigates the difficulty of electrical wiring difficulty since there are only two ring cavities in each stage. As a proof of concept, we fabricate this kind of optical filter with ten stages on silicon-on-insulator platform, with each ring cavity tunable and each stage measurable. We obtain five flat-top responses corresponding to one to five cascading stages. The five-stage filter response has a 3 dB bandwidth of ∼17 GHz, a roll-off rate of ∼−5 dB/GHz at −3 dB point, and an on-chip insertion loss of ∼−6 dB.



Future Energy Efficient Data Centers With Disaggregated Servers

Dec.15, 15 2017

The popularity of the Internet and the demand for 24/7 services uptime is driving system performance and reliability requirements to levels that today's data centers can no longer support. This paper examines the traditional monolithic conventional server (CS) design and compares it to a new design paradigm: the disaggregated server (DS) data center design. The DS design arranges data centers resources in physical pools, such as processing, memory, and IO module pools, rather than packing each subset of such resources into a single server box. In this paper, we study energy efficient resource provisioning and virtual machine (VM) allocation in DS-based data centers compared to CS-based data centers. First, we present our new design for the photonic DS-based data center architecture, supplemented with a complete description of the architectural components. Second, we develop a mixed integer linear programming (MILP) model to optimize VM allocation for the DS-based data center, including the data center communication fabric power consumption. Our results indicate that, in DS data centers, the optimum allocation of pooled resources and their communication power yields up to 42% average savings in total power consumption when compared with the CS approach. Due to the MILP high computational complexity, we developed an energy efficient resource provisioning heuristic for DS with communication fabric (EERP-DSCF), based on the MILP model insights, with comparable power efficiency to the MILP model. With EERP-DSCF, we can extend the number of served VMs, where the MILP model scalability for a large number of VMs is challenging. Furthermore, we assess the energy efficiency of the DS design under stringent conditions by increasing the CPU to memory traffic and by including high noncommunication power consumption to determine the conditions at which the DS and CS designs become comparable in power consumption. Finally, - e present a complete analysis of the communication patterns in our new DS design and some recommendations for design and implementation challenges.



High-Resolution and Low-Loss All-Fiber Spectral Filters Based on Biconic Tapers

Dec.15, 15 2017

A family of narrowband spectral filters based on biconic fiber tapers is investigated. These filters were made of highly-depressed-cladding single-mode fibers by a heat-and-pulling process, and using a cylindrical-tube graphite heater. The evolution of the taper profiles during the pulling of different elongations was modeled by a coupled system of partial differential equations governing the mass and axial momentum conservation. The optical responses were modeled by using the mode coupling theory. Theoretical results, ranging from prediction of the taper profiles to optical responses of these filters—transmission losses, free spectral range, and isolation—show strong accordance with experimental ones.



Graphene Oxide Coated PCF Interferometer for Enhanced Strain Sensitivity

Dec.15, 15 2017

We propose a graphene oxide (GO) coated photonic crystal fiber (PCF) based modal interferometer for strain and temperature sensing. This Mach-Zehnder interferometer based probe has been fabricated by splicing PCF with single mode fiber (SMF) and creating a short collapsed region at one of the SMF-PCF junction and a long collapsed region at the other splicing junction. The PCF along with the collapsed regions is coated with GO prepared by Hummers method. The short collapsed region has been used to excite core and cladding modes in PCF while the long collapsed region is used for better interaction of core and cladding modes with GO. The change in refractive index of GO has been utilized to monitor strain. The uncoated probe shows a strain sensitivity of 1.6 pm/μϵ while the GO coated probe shows a strain sensitivity of 3.1 pm/μϵ, thereby enhancing the strain sensitivity by 93%. Further, the probe shows a temperature sensitivity of 14 pm/°C.



A Temperature-Insensitive Refractive Index Sensor Based on No-Core Fiber Embedded Long Period Grating

Dec.15, 15 2017

A novel long-period fiber grating via periodically embedding no-core fiber (NCF) has been achieved. The 11-period SMF-NCF-SMF-long period fiber grating (SNS-LPG) can exhibit an extremely high loss resonant dip (>20 dB). Theoretical analysis shows good agreement with the measured transmission spectrum. We investigated both refractive index and temperature sensitivity of SNS-LPG. The fabricated sensor achieve an average wavelength sensitivity of 141.837 nm/RIU in the range of 1.333–1.400 RIU, and exhibit lower temperature sensitivity (−6.43 pm/ °C and 0.005 dB/ °C).



Numerical Simulation of Ultrashort Mid-IR Pulse Amplification in Praseodymium-Doped Chalcogenide Fibers

Dec.15, 15 2017

We report the design of an ultrashort pulse amplifier based on using a chalcogenide gain fiber with a praseodymium doped core for operating in the 4–5 μm range on the (3F23H6 ) → 3H5 and 3H53H4 transitions. A detailed numerical simulation with allowance for dispersive and nonlinear effects for two pumping schemes: four-level at 1.55 μm and three-level at 2 μm with different fiber optical losses, pulse repetition rates, and central signal wavelengths is presented. The preferable case is cascade amplification on both laser transitions with overlapping emission cross sections for seeding pulses at 4.3 μm pumped at 1.55 μm. In this case, a gain of more than 30 dB can be achieved. The pulse energy can be increased from 10 pJ up to >10 nJ for the repetition rate of order 1 MHz even for the loss level of 3 dB/m. The produced ps pulses have broadband spectra with Fourier transform limitation of order 100 fs. Further amplification may be limited by fiber damage.



Plane-by-Plane Femtosecond Laser Inscription Method for Single-Peak Bragg Gratings in Multimode CYTOP Polymer Optical Fiber

Dec.15, 15 2017

We report on the development and characterization of single peak fiber Bragg gratings (FBGs) in polymer optical fiber (POF). We use a multimode gradient index cyclic transparent optical polymer (CYTOP) fiber, where the FBGs are inscribed with a femtosecond laser. We adapt the direct-write, plane-by-plane inscription method, where the beam is scanned transversely across the core, to create refractive index changes. In order to reduce the number of fiber modes coupling to the grating, we limit the FBG's spatial extent to the central part of the core, in the region where the gradient index profile peaks. In this way, we are able to excite the strongest lower order modes thereby generating single peak POF-FBG spectra. We support our experimental results with modeling using the bi-directional beam propagation method (Bi-BPM). Furthermore, a FBG array is used as a quasi-distributed sensor, recovering the vibration response of a freely suspended metal beam, using a 6-m sensing strand. The FBGs are multiplexed using a high-speed commercial wavelength demodulator, the output of which provides wavelength- and time-dependent displacement information. The results are compared directly with the performance of a silica-fiber-based FBG sensor array, and show a significant sensor sensitivity improvement for the polymer fiber to dynamic strain.



Tapered Fiber Attached Nitrile Diaphragm-Based Acoustic Sensor

Dec.15, 15 2017

We present a low-cost acoustic sensor using tapered fiber structure attached to a nitrile polymer-based diaphragm. The tapered fiber is attached in the line of symmetry of a circular diaphragm of optimized thickness and diameter. The applied acoustic pressure deforms the diaphragm, which bends the tapered fiber attached with it. The bending induced change in transmission power is utilized to detect the applied acoustic pressure. The acoustic sensitivity and minimum detectable pressure at 2500 Hz are 36 mV/kPa and 21.11 Pa/√Hz, respectively, for the sensor setup with tapered fiber waist diameter of 18.37 μm. The sensor shows a reasonably flat response from 250 to 2500 Hz. The performance parameters of the sensor, such as sensitivity, minimum detectable pressure, and flat response range can be easily tailored by changing the dimensions of diaphragm and tapered fiber.



Polarization Multiplexing With the Kramers-Kronig Receiver

Dec.15, 15 2017

We present two schemes extending the Kramers-Kronig-receiver to polarization multiplexed transmission. One of the schemes relies on the Stokes receiver and allows for complex-valued polarization multiplexed transmission without using a local oscillator, and active polarization control at the receiver. It uses three photodiodes and requires three analog-to-digital converters (ADCs). The other scheme uses a local oscillator, and its implementation is suitable in all cases where the transmitter and the receiver operate at the same wavelength, so that the local oscillator signal can be extracted from the transmit laser. It uses only two photodiodes and two ADCs, and does not require optical hybrids. The performance of the first (Stokes-based) scheme is studied numerically, whereas that of the second scheme is studied both numerically and experimentally.



Numerical and Experimental Investigation of Surface Plasmon Resonance Excitation Using Whispering Gallery Modes in Bent Metal-Clad Single-Mode Optical Fiber

Dec.15, 15 2017

We present a numerical and experimental study of surface plasmon resonance (SPR) excitation in a bent single-mode optical fiber with metalized cladding. It is shown that with a suitable combination of bend radius and metal film thickness surface plasmon waves can be excited in the film as a result of coupling between fundamental and surface plasmon modes via whispering gallery modes supported by the bent fiber cladding. The coupling brings about a dip in the transmission spectrum at the resonant wavelength which is strongly dependent on the ambient refractive index. This enables one to build a fiber optic SPR-refractometer with a standard single-mode fiber without breaking integrity of the fiber or using any additional elements. Refractometric sensitivity of ∼5 μm per refractive index unit and resolution of ∼4·10−6 are experimentally demonstrated for the measured refractive index around 1.43. The reported results may find wide application in bio- and chemosensing.



Measurement of Optical Nonlinear Distortions and Their Uncertainties in Coherent Systems

Dec.15, 15 2017

In this paper, we propose an experimental setup and an uncertainty evaluation to feed our previously proposed semi-analytical model for brisk assessment (SAMBA) of distortions from fiber nonlinearities over heterogeneous fiber spans transmission. We experimentally characterize physical nonlinear parameters required by the SAMBA by setting up a one span test bed and cumulated chromatic dispersion emulation in the transmitter, resulting in a nonlinear noise coefficient curve. We determine the accuracy of our method through the evaluation of the uncertainties impacting the measurement of the nonlinear noise. Finally, we assess the accuracy of our SAMBA performance estimator with a multispan dispersion unmanaged transmission up to 25 spans and show less than 0.5 dB prediction error in the linear and nonlinear regimes.



Compact Low Loss Vertical Coupling for Optical Transmitters With Polymer Modulators

Dec.15, 15 2017

Low-loss optical interconnects in hybrid integrated platforms for silicon photonics are likely to become increasingly important to overcome power consumption limitations in telecom packaging applications. Here, we show a short taper device that effectively interconnects electro-optic polymer modulators waveguides and silicon-on-insulator platforms without altering the polymer modulator fabrication process. We achieved power transmission better than $-text{0.2}$ dB with very good alignment shift tolerance over the whole C-band, by using tapers as short as 179.5  $mu$m.



Venus: A Low-Latency, Low-Loss 3-D Hybrid Network-on-Chip for Kilocore Systems

Dec.15, 15 2017

Network on chip (NoC) with more than 1000 cores is anticipated to meet the requirements of exascale computing in the foreseeable future. As latency is one of the most critical metrics to evaluate performance for kilocore-chip, researchers recently proposed optical networks on chip (ONoCs) with multiwavelength to achieve low latency. Nevertheless, with networks scaling to kilocores and too many wavelengths used, waveguide crossings loss and microring resonators (MRs) pass-by loss on the critical path are increased considerably. In this paper, we propose Venus, a three-dimensional NoC architecture with multiple photonic and electrical layers. By using space division multiplexing and hybrid wavelength assignments method, Venus possesses the following two features: 1) Each core can communicate with any other one in one hop and any two clusters in different subnets can communicate with each other without any blocking, thus reducing latency greatly; and 2) the number of waveguide crossings and also the MRs passed by on the critical path is reduced, thus saving energy consumption considerably. Architectures based on 64-core, 512-core, and 1024-core are simulated respectively. Evaluation results of different synthetic traffic patterns and real applications demonstrate that Venus significantly reduces the end-to-end latency and worst case loss compared to previous proposals.



Nonorthogonal Multiple Access and Carrierless Amplitude Phase Modulation for Flexible Multiuser Provisioning in 5G Mobile Networks

Dec.15, 15 2017

In this paper, a combined nonorthogonal multiple access (NOMA) and multiband carrierless amplitude phase modulation (multiCAP) scheme is proposed for capacity enhancement of and flexible resource provisioning in 5G mobile networks. The proposed scheme is experimentally evaluated over a W-band millimeter wave radio-over fiber system. The evaluated NOMA-CAP system consists of six 1.25-GHz multiCAP bands and two NOMA levels with quadrature phase-shift keying and can provide an aggregated transmission rate of 30 Gbit/s. The proposed system can dynamically adapt to different user densities and data rate requirements. Bit error rate performance is evaluated in two scenarios: a low user density scenario where the system capacity is evenly split between two users and a high user density scenario where NOMA and multiCAP are combined to serve up to 12 users with an assigned data rate of 2.5 Gbit/s each. The proposed system demonstrates how NOMA-CAP allows flexible resource provisioning and can adapt data rates depending on user density and requirements.



On the Design of NFT-Based Communication Systems With Lumped Amplification

Dec.15, 15 2017

Nonlinear Fourier transform (NFT) based transmission technique relies on the integrability of the nonlinear Schrödinger equation (NLSE). However, the lossless NLSE is not directly applicable for the description of light evolution in fibre links with lumped amplification such as Erbium-doped fibre amplifier (EDFA) because of the nonuniform loss and gain evolution. In this case, the path-averaged model is usually applied as an approximation of the true NLSE model including the fibre loss. However, the inaccuracy of the lossless path-average model, even though being small, can also result in a notable performance degradation in NFT-based transmission systems. In this paper, we extend the theoretical approach, which was first proposed for solitons in EDFA systems, to the case of NFT-based systems to constructively diminish the aforementioned performance penalty. Based on the quantitative analysis of distortions due to the use of path-average model, we optimise the signal launch and detection points to minimise the models mismatch. Without loss of generality, we demonstrate how this approach works for the NFT systems that use continuous NFT spectrum modulation (vanishing signals) and NFT main spectrum modulation (periodic signals). Through numerical modelling, we quantify the corresponding improvements in system performance.



A Stable Twin-Core-Fiber-Based Integrated Coupler Fabricated by Thermally Diffused Core Technique

Dec.15, 15 2017

A type of stable integrated couplers based on the twin-core fiber (TCF) is proposed and demonstrated. The integrated coupler is fabricated by heating a piece of TCF with the thermally diffused core technique. During the heating process, the dopant in the cores of the TCF will diffuse to the cladding which leads to expansion of the core mode fields. As a result, the optical power in the two cores can be coupled to each other. Because the external shape of the coupling region of the TCF coupler does not change, such type of couplers have high mechanical strength and stable responses to temperature, strain, and surrounding refractive index changes. The coupling characteristics between the cores of the thermally diffused TCF are theoretically analyzed and experimentally investigated. Results show that the coupler is almost stable when the temperature changed from 30 to 120 °C, the strain changed from $0;{{mathbf mu varepsilon }}$ to $1923;{{mathbf mu varepsilon }}$, and the external refractive index ranged from 1.3435 to 1.3676.



A Thank You to All Our Reviewers

Dec.15, 2017

The publication offers a note of thanks and lists its reviewers.



2017 Index IEEE/OSA Journal of Lightwave Technology Vol. 35

Dec.15, 2017

This index covers all technical items - papers, correspondence, reviews, etc. - that appeared in this periodical during the year, and items from previous years that were commented upon or corrected in this year. Departments and other items may also be covered if they have been judged to have archival value. The Author Index contains the primary entry for each item, listed under the first author's name. The primary entry includes the co-authors' names, the title of the paper or other item, and its location, specified by the publication abbreviation, year, month, and inclusive pagination. The Subject Index contains entries describing the item under all appropriate subject headings, plus the first author's name, the publication abbreviation, month, and year, and inclusive pages. Note that the item title is found only under the primary entry in the Author Index.



Information For Authors

Dec.15, 2017

Provides instructions and guidelines to prospective authors who wish to submit manuscripts.



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Dec.15, 2017

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