Passive Fiber Components Research Articles

Nanostructured Large Mode Area Fiber for Laser Applications

We developed a passive silica based large mode area fiber with the nanostructured core with a diameter of 30 m devoted to fiber Bragg grating inscription for application in an all-fiber laser cavity. The fiber is perfectly matched to the commercial active fiber with NA=0.06 and core/cladding diameters 30/250 m. Measured modal characteristics and bending loss of the fiber confirm single-mode operation for bending diameter of 8 cm with bending losses as low as 0.15 dB/m. Although the nanostructured fiber core is low germanium doped, we fabricated high reflectivity (98.5%) UV induced fiber Bragg grating (FBG) and verified its performance in fiber laser setup. The laser cavity formed with highly reflective FBG inscribed in the fiber and Fresnel reflection on the free end of active fiber results in lasing efficiency of 65.5%. The flexibility of the nanostructuring approach gives prospects for the development of free-form large mode area fibers for passive fiber components and matched with any type of active fibers.

Observation of split evanescent field distributions in tapered multicore fibers for multiline nanoparticle trapping and microsensing.

The optical attractive force in tapered single-mode fibers (SMFs) is usually uniformly distributed around the tapered section and has been found to be important for trapping and manipulating targeted atoms and nanoparticles. In contrast, a peculiar phenomenon of the evanescent field splitting along the azimuth axis can be experimentally observed by tapering a weakly-coupled MCF into a strongly-coupled MCF to generate supermode interference. Moreover, the supermode interference produces a hexagonally distributed evanescent field and its six vertices give rise to the multiline optical attractive force. For such spectral resonances, the optimum extinction ratio for the transmission dips is given by 47.4 dB, this being determined using an index liquid to cover the tapered MCF. The resonant dips move to a greater extent at longer wavelengths, with the optimum tuning efficiency of 392 nm/RIU for index sensing. The split evanescent fields respectively attract the excited upconversion nanoparticles in the liquid to be linearly aligned and running down the tapered region over the fiber surface, emitting green light with 60° symmetry. The charged nanoparticles were periodically self-organized, with a period of around 1.53 µm. The parallel lines, with 60° rotational symmetry, can be useful for (1) indicating the exact locations of the side-cores or orientations of the tapered MCF; (2) as precision alignment keys for micro-optical manipulation; and (3) enhancing the upconversion light, or for use in lasers, coupling back to the MCF. The split evanescent fields can be promising for developing new evanescent field-based active and passive fiber components with nano-structures.

The combined effects of intra-cavity spectral filtering on the fiber mode-locked laser

In this paper, we report on the influences of gain non-uniformity, Lyot filter effect and transmission spectrum of the passive fiber components on the spectral profile of a semiconductor saturable absorber mirror (SESAM)-based ytterbium (Yb)-doped mode-locked fiber laser. Simulation and experimental results prove that the adjustment of the Lyot filter will be an effective way to control the output spectrum during the actual application and manufacture of the mode-lock fiber laser.

High-Power Passive Fiber Components for All-Fiber Lasers and Amplifiers Application—Design and Fabrication

The most important components for application in high-power all-fiber lasers and amplifiers are, most of all, power combiners, but also mode field adaptors. This paper summarizes recent achievements in the area of development and fabrication of high-power passive fiber components. The principles of operation and basic design and fabrication criteria, which have to be taken into account while designing the aforementioned components, are explained in detail. The most recent impressive achievements are summarized and described.

40 W All-Fiber Er/Yb MOPA System Using Self-Fabricated High-Power Passive Fiber Components

In this work, we demonstrate a three-stage all-fiber master oscillator power amplifier (MOPA) system emitting over 40 W of continuous-wave (CW) output power at ~1.5 µm. The setup utilizes three self-fabricated high-power passive fiber components: a mode-field adaptor (MFA) and two types of pump and signal power combiners. Their development allowed us to become independent from commercially available components, which are often incompatible with fibers used in the experimental setups, resulting in additional losses. A power combiner with single-mode (SM) signal fibers in a configuration (5 + 1) × 1 was used in the second stage of the MOPA system, which was based on an SM Er–Yb co-doped double-clad (DC) fiber. The fabricated MFA was used to connect the second amplifier stage based on SM fibers with the third amplifier stage based on large-mode-area (LMA) fibers. In the third stage of MOPA system, based on Er–Yb LMA DC fibers, we used the fabricated power combiner based on LMA-type signal fibers in a configuration (6 + 1) × 1. The presented three-stage MOPA system, utilizing self-fabricated high-power passive fiber components, enables amplification of an input signal of 10 mW up to 44 W of the CW power at the wavelengths of 1555 nm and 1563 nm, corresponding to a gain level of approximately 36.4 dB.

Enhanced Pump Absorption of Active Fiber Components With Skew Rays

We propose a model and then demonstrate a technique that can be used to optimize pump absorption in active multimode fibers with different cladding geometries, by varying the angle of pump light excitation. The analysis of the contribution of different ray groups at different wavelengths enables the design optimization of active and passive fiber components in fiber lasers.

A kW Continuous-Wave Ytterbium-Doped All-Fiber Laser Oscillator with Domestic Fiber Components and Gain Fiber**Supported by the National High-Technology Research and Development Program of China under Grant No 2013AA031501, and the Fundamental Research Funds for the Central Universities under Grant No 2014TS017.

We demonstrate a kW continuous-wave ytterbium-doped all-fiber laser oscillator with all domestic fiber components: a 7 × 1 fused fiber bundle combiner, a fiber Bragg grating and a double-clad gain fiber. The oscillator operates at 1079.48 nm with 80.94% slope efficiency and shows no limit of temperature and nonlinear effects. These indicate that the passive fiber components and the gain fiber are all qualified for the high power environment. No evidence of the signal power roll-over shows that this oscillator possesses the capacity to higher output with available pump power.

CETO—Centro de Ciências e Tecnologias Opticas, Trends in Optical Fibre Metrology and Standards

Summer School, 27 June to 8 July 1994, Viana do Castelo, Hotel do Parque, PortugalOptical fibres, with their extremely low transmission loss, untapped bandwidth and controllable dispersion, dominate a broad range of technologies in which applications must respond to the increasing constraints of today's specifications as well as envisage future requirements.Optical fibres dominate communications systems. In the area of sensors, fibre optics will be fully exploited for their immunity to EMI, their high sensitivity and their large dynamic range.The maturity of single mode optical technology has led to intensive R&D of a range of components based on the advantages of transmission characteristics and signal processing.Specifications and intercompatibility requests for the new generation of both analogue and digital fibre optical components and systems has created a demand for sophisticated measuring techniques based on unique and complex instruments.In recent years there has been a signification evolution in response to the explosion of applications and the tightening of specifications. These developments justify a concerted effort to focus on trends in optical fibre metrology and standards.ObjectiveThe objective of this school is to provide a progressive and comprehensive presentation of current issues concerning passive and active optical fibre characterization and measurement techniques. Passive fibre components support a variety of developments in optical fibre systems and will be discussed in terms of relevance and standards. Particular attention will be paid to devices for metrological purposes such as reference fibres and calibration artefacts.The characterization and testing of optical fibre amplifiers, which have great potential in telecommunications, data distribution networks and as a system part in instrumentation, will be covered.Methods of measurement and means of calibration with traceability will be discussed, together with the characterization requirements of the new generation of analogue and digital fibre optical systems, which require sophisticated measurement techniques employing complex instruments unique to optical measurements.The school will foster and enhance the interaction between material, devices, systems, and standards-oriented R&D communities, as well as between engineers concerned with design and manufacturers of systems and instrumentation.Topics Review of optical fibre communication technology and systems Measurement techniques for fibre characterization: Reliability and traceability Reference fibres and calibration artefacts Ribbon fibres Mechanical and environmental testing Fibre reliability Polarimetric measurements Passive components characterization: Splices and connectors Couplers, splitters, taps and WDMs Optical fibres and isolators WDM technologies and applications: WDM technologies Tunable optical filters Fibre amplifiers and sources: Performances and characterization Design and standards Nonlinear effects Subsystem design and standards: Design and fabrication techniques Performance degradation and reliability Evaluation of costs/performance/technology Sensors IR - optical fibres Plastic fibres InstrumentationRegistrationParticipation free of charge for postgraduate students, with some grants available for travel and lodging expenses.All correspondence should be addressed to: Secretariat, Trends in Optical Fibre Metrology and Standards, a/c Prof. Olivério D D Soares, Centro de Ciências eTecnologias Opticas, Lab. Fisica - Faculdade de Ciências, Praça Gomes Teixeira, P-4000 Porto, Portugal. Tel: 351-2-310290, 351-2-2001648; Fax: 351-2-319267.

Analysis of etching-induced birefringence changes in elliptic core fibers

A mathematical model is presented that predicts birefringence changes in an optical fiber as the cladding is removed. This model approximates a highly elliptical fiber core with a rectangular dielectric waveguide. The birefringence calculations obtained with the model compare well with experimental evidenceobtained with real-time birefringence monitoring during cladding removal by chemical etching. The information is used to control the amount of cladding removed from a D fiber to within approximately 0.05 microm for use in the production of passive optical fiber components.

Active and passive fibre components

The development of optical fibres for transmission has given us an advanced technology capable of producing waveguides of unequalled transparency and axial uniformity. This can be adapted to produce a range of active and passive components that have many advantages, including their suitability for connection into optical fibre systems. These may in turn enable more complex frequency-selective systems to be built economically. Passive components include resonators and reflectors with very low loss and linewidths that are comparable with the modulation rates, possibly allowing radio type filtering and separation; splitters and separators with a wide variety of characteristics and polarization-selective components. In each case the performance achieved is better than that achieved by any other method. Active devices include laser sources and amplifiers of various types and nonlinear switches and pulse compressors; these too show performance ahead of that achieved by other means. This paper reviews these results and discusses applications to broadband networks.

Optical fiber up-tapers with high beam expansion ratios for component fabrication

Optical fibre up-tapers with beam expansion ratios of 10, about twice the previously achieved value for the same taper outer diameter, have been fabricated and characterized. The increased beam expansion is achieved with a near step-index profile for the core of the taper. The excess coupling loss between two tapers is less than 0.1 dB. A lateral offset of more than 20 mu m or an axial displacement of 4 mm between tapers caused an excess loss of 1 dB. The angular tolerance for this loss is a manageable 0.3 degrees . These tapers permit, for a given beam expansion ratio, the manufacture of smaller outer diameter, more compact structures of self-aligned beam expansion. They also permit the insertion of optical elements into the expanded beam for the fabrication of inline single-mode passive fiber components.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Bandwidth and modal noise effects in fused-head-end multimode fiber passive components

Passive multimode fiber components, particularly 1-to-2 splitters/couplers, manufactured using the fused-head-end technique, are tested under network conditions. The mode power transfer matrix and its effects on the network are discussed. The modification of the pulse mode spectrum in the splitter is analyzed by studying the pulsewidth variation and the transmitted pulse power for components at the near and far end of a long length of fiber. The modal noise generated in such passive fiber components is determined, and the modal noise ratio (MNR) and the modal noise susceptibility (MNS) are introduced as figures of merit characterizing modal noise sources and multimode fiber passive components, respectively. >

Single-mode fiber components

A variety of optical components have been made directly from single-mode fibers. These components can be combined to construct in-line all-fiber systems such as fiber gyroscopes, fiber Raman lasers, local area networks, or coherent lightwave systems. This paper reviews the present state of passive and active single-mode fiber components. Passive components are polarizers, directional couplers, filters, and Faraday rotators. Active components require external control or optical power and include modulators, polarization controllers, frequency shifters, and amplifiers. Polarization is usually important in fiber components and discussions of polarization-maintaining and ordinary single-mode fibers are included.

Single-mode-fibre passive components made in the fused-head-end technique

The fused-head-end technique, used successfully until now for producing passive fibre components in multimode fibre, can also be applied to produce single-mode fibre couplers and splitters. The device is based on evanescent mode coupling and has no pigtail problem. The first experimental results are presented, together with the theoretical interpretation. Some expected system applications and further improvements are indicated.

Differential mode loss and mode conversion in passive fiber components measured using the chromatic launching and the central spot far field techniques

Mode spectra launched conventionally and using the chromatic launching (CL) method are analyzed using the central spot far field (CSFF) method. This is applied to study the differential mode loss and mode conversion properties of passive optical fiber components manufactured using the fused-head-end (FHE) technique.

Passive components for multimode fiber-optic networks

A new manufacturing technique is described by which all types of passive optical fiber components required in a network can be made.