A model for the shape of optical fiber tapers, formed by stretching a fiber in a heat source of varying length, is presented. Simple assumptions avoid any need for the techniques of fluid mechanics. It is found that any decreasing shape of taper can be produced. The procedure for calculating the hot-zone length variation required to produce a given shape of taper is described, and is used to indicate how an optical adiabatic taper can be made. A traveling burner tapering system is capable of realizing the model's prediction, and a complete practical procedure for the formation of fiber tapers with any reasonable shape is thus presented. >

The shape of fiber tapers

Optical fiber gratings have developed into a mature technology with a wide range of applications in various areas, including physical sensing for temperature, strain, acoustic waves and pressure. All of these applications rely on the perturbation of the period or refractive index of a grating inscribed in the fiber core as a transducing mechanism between a quantity to be measured and the optical spectral response of the fiber grating. This paper presents a relatively recent variant of the fiber grating concept, whereby a small tilt of the grating fringes causes coupling of the optical power from the core mode into a multitude of cladding modes, each with its own wavevector and mode field shape. The main consequence of doing so is that the differential response of the modes can then be used to multiply the sensing modalities available for a single fiber grating and also to increase the sensor resolution by taking advantage of the large amount of data available. In particular, the temperature cross-sensitivity and power source fluctuation noise inherent in all fiber grating designs can be completely eliminated by referencing all the spectral measurements to the wavelength and power level of the core mode back-reflection. The mode resonances have a quality factor of 105, and they can be observed in reflection or transmission. A thorough review of experimental and theoretical results will show that tilted fiber Bragg gratings can be used for high resolution refractometry, surface plasmon resonance applications, and multiparameter physical sensing (strain, vibration, curvature, and temperature).

Tilted fiber Bragg grating sensors

Graphene is an optical material of unusual characteristics because of its linearly dispersive conduction and valence bands and the strong interband transitions. It allows broadband light-matter interactions with ultrafast responses and can be readily pasted to surfaces of functional structures for photonic and optoelectronic applications. Recently, graphene-based optical modulators have been demonstrated with electrical tuning of the Fermi level of graphene. Their operation bandwidth, however, was limited to about 1 GHz by the response of the driving electrical circuit. Clearly, this can be improved by an all-optical approach. Here, we show that a graphene-clad microfiber all-optical modulator can achieve a modulation depth of 38% and a response time of ∼2.2 ps, limited only by the intrinsic carrier relaxation time of graphene. This modulator is compatible with current high-speed fiber-optic communication networks and may open the door to meet future demand of ultrafast optical signal processing.

/pdf/ultrafast-all-optical-graphene-modulator-29dpuypdgs.pdf

Ultrafast All-Optical Graphene Modulator

Two complementary delineation criteria are presented which provide guidelines to the design of relatively short, low-loss tapered fibres and devices. They are used to explain anomalous loss effects in depressed-cladding and W-fibres, as well as the difficulty in fabricating low-loss devices by tapering such fibres. Practical application of the criteria to couplers, beam expanders and abrupt taper filters is summarised. The accompanying paper provides both experimental and theoretical justification for the delineation criteria.

Tapered single-mode fibres and devices. I. Adiabaticity criteria

We propose simple and compact methods for implementing all-fiber interferometers. The interference between the core and the cladding modes of a photonic crystal fiber (PCF) is utilized. To excite the cladding modes from the fundamental core mode of a PCF, a coupling point or region is formed by using two methods. One is fusion splicing two pieces of a PCF with a small lateral offset, and the other is partially collapsing the air-holes in a single piece of PCF. By making another coupling point at a different location along the fiber, the proposed all-PCF interferometer is implemented. The spectral response of the interferometer is investigated mainly in terms of its wavelength spectrum. The spatial frequency of the spectrum was proportional to the physical length of the interferometer and the difference between the modal group indices of involved waveguide modes. For the splicing type interferometer, only a single spatial frequency component was dominantly observed, while the collapsing type was associated with several components at a time. By analyzing the spatial frequency spectrum of the wavelength spectrum, the modal group index differences of the PCF were obtained from 2.83×10-3 to 4.65 ×10-3 . As potential applications of the all-PCF interferometer, strain sensing is experimentally demonstrated and ultra-high temperature sensing is proposed.

All-fiber Mach-Zehnder type interferometers formed in photonic crystal fiber.

Field evolution along longitudinally nonuniform finite-cladding fibers of circularly symmetric cross section is analyzed in terms of coupled modes. Local modes are used for abruptly tapered fibers, whereas linear-index fiber modes provide the expansion basis for Kerr-type nonlinear-index fibers. Convergence of the results suggests in both cases that only a finite number of bound modes is sufficient to describe the field adequately. A comparison with simulations given by a finite-difference beam-propagation method that was developed for circularly symmetric waveguides confirms the validity of this assumption.

Mode coupling in nonuniform fibers: comparison between coupled-mode theory and finite-difference beam-propagation method simulations

The analysis of fused biconical single-mode fiber couplers shows that, as opposed to other types of single-mode fiber coupler, the coupling mechanism is not associated with evanescent waves and that the infinite cladding approximation is not valid. The two original claddings must be considered, after fusion and stretching, to form a single guide whose asymmetric excitation gives rise to the well-known beat phenomenon between two normal modes of the guide. For calculation purposes, this asymmetrically excited single guide is modeled into a pair of equivalent circular guides tangent to each other and having the same longitudinal profile as the real structure. The experimental results are compared with the theory.

Analyse d'un coupleur bidirectionnel a fibres optiques monomodes fusionnees.

In considering the wavelength-dependent transmission of tapered fibers we provide an observation of the fringe that shows the least response to variations in wavelength and that is, by definition, the achromatic fringe. This is a manifestation of the equalization of the HE11–HE12 group velocity occurring at V = 4.4. The fact that it was observed in a tapered single-mode fiber confers some particular features that are discussed and compared with those of other two-mode guides with regard to sensor applications.

Tapered-fiber interferometric wavelength response: the achromatic fringe.

An abruptly tapered fiber can be essentially divided into three different regions: one beating region in its central, quasi-cylindrical part, lying between two coupling regions, where the slopes are large. In this paper we report two experiments which help to visualize and analyze the beating region. We show that, in this region, there are principally two modes present, HE11 and HE12, both excited with large amplitudes.

Investigation of power oscillations along tapered monomode fibers.

The capability of changing the optical output of a tapered single-mode fiber by using a liquid crystal as an electro-optical medium is shown.

Liquid-crystal-clad tapered fibers.

Handle everyday research tasks with reliable, citation-backed results

Your personal Research Agent to handle research tasks with citation-backed results

Popular Tasks used by Researchers

How can I help with your research?

Meet SciSpace

Get more enhanced response by uploading the PDFs you want me to reference.

No relevant PDFs in your library

SciSpace is the AI research assistant for academics. Run systematic literature reviews on 280M+ papers, and write papers with cited sources. Trusted by 1M+ students, PhDs & researchers.

SciSpace | AI for Research

Analyze PDFs

Code & Manuscripts

Funding & Grants

Literature & Patents

Medical & Clinical Data

Systematic Review

Visualize & Present

Web & Data

Build a Google Scholar-like website for your research.

Build a website

Create charts and images for your research

Create a Chart

Write a paper for submission to a journal

Draft a manuscript

Patent Search

Design eye-catching scientific posters in minutes.

Scientific Poster Generation

Systematic Literature Review

One task is running at the moment. Your messages will be shown right after.

Drag and drop or click here to browse

Loved by <highlight>1 million+</highlight> researchers

Extract a list of specific topics and their sources from unstructured text

Topics

Compare and analyze relevant papers that matches with your search

Papers

Get insights from PDFs and bookmarked papers from your library

My library

Recent searches

Try searching for:

Catch AI-generated content in scholarly and non-scholarly content

{ai} Detector

Ai Writer

Get PDF Summaries, highlighted text explanations 

Chat with PDF

Effortlessly create in-text citations and bibliographies in APA and 2,500 other formats

Citation generator

Get explanations, summaries, and answers on academic papers

Ease up your research workflow with {scispace}'s cohort of exciting AI tools

Elevate your academic writing skills and convey your ideas the way you want

Paraphraser

Explore our range of reading and writing tools

Your file is being prepared and should be ready in a few minutes. If it's a large file, it might take a bit longer. You can close this window, and we'll email you the file when it's done.

You have reached a maximum limit of <strong>{limit}</strong> columns in the table. Remove at least <strong>1</strong> column to add or create another one.

Jacques Bures

Author Tools

Chat about Author