Passive Optical Fiber Research Articles

Producing regenerated gratings in hydrogen-loaded single mode fiber by heat treatment

The fiber Bragg grating (FBG) is a passive optical fiber component with the refractive index modulated along the fiber length and has been widely applied in fiber sensing systems. High-temperature stable fiber gratings are promising for uses at high temperatures and attract extensive attention. In this paper, FBGs were inscribed in hydrogen loaded standard single mode fibers with the 248-nm excimer laser, and regenerated gratings were obtained through heat treatment. The shift of the central wavelength of the regenerated FBG had a good linearity with temperature, and the reflectivity of the regenerated FBG could almost keep unchanged at 800 °C.

Stem effect of a Ce3+ doped SiO2 optical dosimeter irradiated with a 192Ir HDR brachytherapy source

Fiber-optic-coupled scintillation dosimeters are characterized by their small active volume if compared to other existing systems. However, they potentially show a greater stem effect, especially in external beam radiotherapy where the Cerenkov effect is not negligible. In brachytherapy, due to the lower energies and the shorter high dose range of the employed sources, the impact of the stem effect to the detector accuracy might be low. In this work, the stem effect of a Ce3+ doped SiO2 scintillation detector coupled to a SiO2 optical fiber was studied for high dose rate brachytherapy applications. Measurements were performed in a water phantom at changing source-detector mutual positions. The same irradiations were performed with a passive optical fiber, which doesn't have the dosimeter at its end. The relative contribution of the passive fiber with respect to the uncorrected readings of the detector in each one of the investigated source dwell positions was evaluated. Furthermore, the dosimeter was calibrated both neglecting and correcting its response for the passive fiber readings. The obtained absolute dose measurements were then compared to the dose calculations resulting from the treatment planning system. Dosimeter uncertainties with and without taking into account the passive fiber readings were generally below 2.8% and 4.3%, respectively. However, a particular exception results when the source is positioned near to the optical fiber, where the detector underestimates the dose (−8%) or at source-detector longitudinal distances higher than 3cm.The obtained results show that the proposed dosimeter might be adopted in high dose rate prostate brachytherapy with satisfactory accuracy, without the need for any stem effect correction. However, accuracy further improves by subtraction of the noise signal produced by the passive optical fiber.

Ultraweak long-range interactions of solitons observed over astronomical distances

We report what we believe is the weakest interaction between solitons ever observed. Our experiment involves temporal optical cavity solitons recirculating in a coherently-driven passive optical fibre ring resonator. We observe two solitons, separated by up to 8,000 times their width, changing their temporal separation by a fraction of an attosecond per round-trip of the 100 m-long resonator, or equivalently 1/10,000 of the wavelength of the soliton carrier wave per characteristic dispersive length. The interactions are so weak that, at the speed of light, they require an effective propagation distance of the order of an astronomical unit to fully develop, i.e. tens of millions of kilometres. The interaction is mediated by transverse acoustic waves generated in the optical fibre by the propagating solitons through electrostriction.

Design and Implementation of a Practical FTTH Network

Fiber-to-the-Home (FTTH) has long been recognized as a technology that provides future proof bandwidth [1], but has generally been too expensive to implement on a wide scale. However, reductions in the cost of electro-optic components and improvements in the handling of fiber optics now make FTTH a cost effective solution in many situations. The transition to FTTH in the access network is also a benefit for both consumers and service providers because it opens up the near limitless capacity of the core long-haul network to the local user. In this paper individual passive optical components, transceivers, and fibers has been put together to form a complete FTTH network. Then the implementation of the under construction Baghdad/Al-Gehad FTTH network is presented according to the available information from Iraq Telecommunication Post and Company (ITPC). In this work designing, planning and deploying of FTTH network based on Gigabit Passive Optical Network (GPON) will be evaluated in order to obtain an optimal practical sample when designing and implementing any FTTH network.

Optical Fiber Technology 2012

Abstract The Conference on Optical Fibers and Their Applications, Nałȩczów 2012, in its 14th edition, which has been organized since more than 35 years, has summarized the achievements of the local optical fiber technology community, for the last year and a half. The conference specializes in developments of optical fiber technology, glass and polymer, classical and microstructured, passive and active. The event gathered around 100 participants. There were shown 60 presentations of 20 research and application groups active in fiber photonics, originating from academia and industry. Topical tracks of the Conference were: photonic materials, planar waveguides, passive and active optical fibers, propagation theory in nonstandard optical fibers, and new constructions of optical fibers. A panel discussion concerned teaching in fiber photonics. The conference was accompanied by a school on Optical Fiber Technology. The paper summarizes the chosen main topical tracks of the conference on Optical Fibers and Their Applications, Nałȩczów 2012. The papers from the conference presentations will be published in Proc. SPIE, including a conference version of this paper. The next conference of this series is scheduled for January 2014 in Białowie˙za.

High-resolution, lensless endoscope based on digital scanning through a multimode optical fiber

We propose and experimentally demonstrate an ultra-thin rigid endoscope (450 μm diameter) based on a passive multimode optical fiber. We use digital phase conjugation to overcome the modal scrambling of the fiber to tightly focus and scan the laser light at its distal end. By exploiting the maximum number of modes available, sub-micron resolution, high quality fluorescence images of neuronal cells were acquired. The imaging system is evaluated in terms of fluorescence collection efficiency, resolution and field of view. The small diameter of the proposed endoscope, along with its high quality images offer an opportunity for minimally invasive medical endoscopic imaging and diagnosis based on cellular phenotype via direct tissue penetration.

Phosphate glasses for optical fibers: Synthesis, characterization and mechanical properties

Phosphate glasses (P2O5–Al2O3–Li2O–B2O3–BaO–La2O3) are studied in the present work for the fabrication of passive optical fiber for amplifier and laser applications. Innovative phosphate glasses with large stability toward crystallization (more than 200°C), low transition temperatures (477°C) and low thermal expansion coefficient (10×10−6°C−1) have been successfully produced. Thermo-mechanical and optical properties of the glasses are presented and discussed with respect to the glass composition. Specific care was used to the design and fabrication of two glasses with adequate thermo-mechanical properties to be suitable in the fiber drawing process. Due to the inner surface quality of the tubes manufactured by the rotational casting, the fiber presents very high quality interface between the core and the cladding. Mechanical characterization of the obtained fibers allowed the evaluation of tensile strengths of the order of 200–500MPa and a Weibull modulus of about 10.

Self-similar propagation region in passive optical fibers based on low-order approximation

For the first time, we numerically demonstrate that similaritons in passive fibers can only propagate with parabolic profile without oscillations in a limited self-similar propagation region when low-order approximation is applied. Dispersion-decreasing fiber (DDF) and nonlinearity increasing fiber (NIF) are used here to generate self-similar pulse in different passive ways. Moreover, we put forward several self-similar features to judge effective similariton propagation and determine self-similar region by numerical simulations and waveform observation. Finally we compare in DDF and NIF the dependence of these regions on incident pulse and fiber parameters in order to obtain parabolic similariton more effectively and steadily. These results extend the low-order propagation properties in passive fibers and are beneficial for the generation of high-quality similariton pulse by parameter selection in experimental studies and practical applications.

Study of Lanthanum Aluminum Silicate Glasses for Passive and Active Optical Fibers

We are reporting onSiO2‐Al2O3‐La2O3glasses—with and withoutYb2O3—suitable for nonlinear and fiber laser applications. We will also be presenting successful supercontinuum generation and fiber laser operation around 1060 nm in step‐index fibers. We optimized the glass compositions in terms of thermal and optical requirements for both a highLa2O3andYb2O3concentration and good compatibility with a silica cladding. We also produced bulk samples, unstructured fibers, and structured fibers with aSiO2‐Al2O3‐La2O3core and silica cladding for this purpose.

Supercontinuum Generation over 2 µm

Effective supercontinuum generation in fiber mediain spectral range over 2 μm was experimentallydemonstrated. Supercontinuum generation wasobserved in passive optical fibers. Maximumspectral broadening was obtained in germaniumdopedfibers with longest wavelength near 2.7 μm.To provide high spectral density we used opticalfiber amplifiers. Thus supercontinuum generationwas obtained in holmium optical fiber amplifiersmedium with spectral density 10 W/nm, in therange from 2 to 2.5 μm. In thulium fiber amplifiersobserved amplification not only in conventionalrange near 1.8 μm, but in spectral range from 2.3 to2.5 μm, that corresponds to 3H4→ 3H5 opticaltransition possibility in thulium-doped opticalfibers.

An Integrated Long-Reach PON and GI-POF In-House Network Architecture for Hybrid CATV/OFDM Signals Transmission

We propose and demonstrate an integrated long- reach passive optical network (PON) and in-house graded-index plastic optical fiber (GI-POF) network architecture for hybrid community antenna television (CATV) and orthogonal frequency division multiplexing (OFDM) signals transmission. By reasonably multiplexing the OFDM and CATV signals into a CATV transmitter, both signals originated from a central office (CO) are successfully transmitted over a span of 60 km single mode fiber (SMF) and another span of 25 m GI-POF to consumers' devices. Although the SMF and GI-POF have different core sizes and attenuation features, no any bridge circuit or wavelength converter is utilized in the proposed architecture resulting in a transparent platform for the Internet service providers (ISPs) to directly manage their long-distance services toward suburban or rural areas. Since the optical signal generated at the CO can be transmitted straightforward to the consumers' devices, the average packet delay and packet overhead size can be greatly reduced and the quality of services (QoS) can be maintained easier. Good experimental performances of the CATV and OFDM signals transmission proof the practice and efficiency of this proposal to extend multimedia services from metro areas to suburban and rural areas.

Research of DC Current Measurement Technology Based on Optical Fiber Thermometry

Thin film sensor has the advantages of small size and low cost, which has become a research hotspot in recent years. A measurement system of passive optical fiber DC current sensor based on the thin film sensors is designed in this article. Designs of electric-heating converter, heating-light converter and low-voltage measurement display system are introduced in detail. Experimental results indicate that the general linear correlation between the time constant of fluorescent lifetime and the voltage across the thin film resistor. The feasibility of measurement system is verified via the results of the experiment.

Basic prerequisites for limit-cycle oscillations within a synchronously pumped passive optical nonlinear fiber-ring resonator

By taking into account Kerr nonlinearity and negative second-order dispersion, we show by numerical investigations that in a passive optical nonlinear fiber ring resonator synchronously pumped with femtosecond pulses a temporal delay via a resonator length detuning or via third-order dispersion leads to limit cycle behavior, which is represented by an oscillatory evolution of the temporal as well as the spectral pulse shape. By introducing a two-dimensional iterative map, we show that limit cycles arise due to the mutual coupling of different spectral pulse components. The resulting system behavior can be used to introduce additional adjustable frequency components into frequency combs.

Selected papers in nonlinear dynamics in dissipative and discrete optical systems

In recent years much attention has been devoted to the study of intrinsic localization of light, i.e. the formation of solitons, in realistic nonlinear systems. This concerns essentially settings where the energy exchange with the environment (dissipative systems) and the noninstantaneous nonlinear response of the respective nonlinear material are taken into account. Another interesting aspect in nonlinear physics is the role of discreteness. Energy exchange (or dissipation) and the noninstantaneous response affect to a large extent the action of the nonlinearity, whereas discreteness offers new opportunities to control the linear properties of the system. Consequently, all these effects and their interplay will evoke a plethora of new soliton solutions. This special issue of Applied Physics B contains selected results of the DFG Research Unit 512 ‘Nonlinear spatio-temporal dynamics in dissipative and discrete optical systems’ together with guest contributions of Stefano Longhi, Politecnico di Milano, and the group of Zhigang Chen, San Francisco State University. The subject looked at by the Research Unit was in its infancy when we started our project. Meanwhile, it has attracted a great deal of interest and lies well in the mainstream of contemporary research in optics. In order to identify the wealth of the underlying physics, we looked at various optical systems spanning from fairly simple ones such as passive and active optical fibers and media exhibiting a secondor third-order nonlinearity to more

From molecular precursors in solution to microstructured optical fiber: a Sol-gel polymeric route

Solid-core photonic crystal fibers with the core derived from non-doped or Erbium-doped sol-gel silica rods are fabricated. The results demonstrate that the direct polymeric sol-gel route constitutes a promising method to prepare large high quality glass pieces that can be integrated into microstructured optical fibers suitable for passive and active optical fiber applications.

All-fiber ultra-narrow linewidth 50 pm Tm3+-doped double-clad fiber laser at 1948 nm

A high stability all-fiber LD-clad-pumped Tm3+-doped fiber laser was reported. The fiber laser had the ultra-narrow linewidth 50 pm at 1.948 μm with the maximal output power of 12.8 W. The slope efficiency was 28.9%, and threshold was 5.7 W. The double-clad Tm3+-doped fiber core was multi-mode, which had a demission of 25/250 μm with the core NA of 0.1 and inner-clad NA of 0.46. The high reflectivity coupler FBG was directly written into the single-mode passive photosensitive optical fiber core, which had a core diameter of 15 μm and NA of 0.1. The cavity was build-up by the high reflectivity FBG and the output fiber end Fresnel reflectivity.

Diagnostics of femtosecond laser pulses based on generation of nonlinear-dispersive similariton

We propose and test experimentally a method, alternative to the autocorrelation technique, for determination of the duration of femtosecond laser pulses. The method is based on generation of nonlinear-dispersive similariton in a passive optical fiber (without gain) and measuring its spectral width (or duration) determined by the power of the initial pulse.

Nonlinear dispersive similariton: spectral interferometric study

A similariton formed in a passive optical fibre is experimentally found and investigated by spectral interferometry completely characterising the complex radiation field. A nonlinear dispersive character of similariton formation leads to chirp linearisation and spectrotemporal similarity of this similariton.

Investigations of Repetition Rate Stability of a Mode-Locked Quantum Dot Semiconductor Laser in an Auxiliary Optical Fiber Cavity

We have investigated experimentally the pulse train (mode beating) stability of a monolithic mode-locked multi-section quantum-dot laser with an added passive auxiliary optical fiber cavity. Addition of the weakly coupled (? -24 dB) cavity reduces the current-induced shift d?/dI of the principal peak in the RF spectrum (the effective pulse repetition frequency) by more than an order of magnitude, from -39.5 to -2.3 kHz/mA. The rms timing jitter of the pulse train is simultaneously reduced from 1.4 to 0.9 ps.

Modeling the inhibition of stimulated Raman scattering in passive and active fibers by lumped spectral filters in high power fiber laser systems

We report on the simulation of stimulated Raman scattering inhibition by lumped spectral filters both in passive optical transport fibers and in fiber amplifiers. The paper includes a detailed theoretical study that reveals the parameters that have the strongest influence on the suppression of the Raman scattering, such as the filter distribution and the insertion losses at the signal wavelength. This study provides guidelines for the use of spectral filtering elements, such as long period gratings, for Raman scattering inhibition in real-world high power fiber amplifiers.