1,720,997 research outputs found
Fabrication of Al<sub>2</sub>O<sub>3</sub> co-doped optical fibres by a solution-doping technique
No full textA new technique for fabricating optical fibres containing Al2O3 is described. Application of the technique to single-mode and rare-earth-doped fibres is discusse
Recent developments in rare-earth-doped fibres and fibre lasers
No full textThe development of techniques to produce single-mode rare-earth-doped fibres has led to many passive and active (laser) devices based on these fibres including distributed temperature sensors, high-rejection wavelength selective filters, and fibre lasers and amplifiers. The possibilities offered by fibre lasers and amplifiers are particularly exciting since they present a potential technique for achieving compact, tunable, diode-pumped, narrow-linewidth sources which are compatible with optical fibre technology. Recent developments include diode-pumped fibre lasers operating at 1.08µm with C.W. output powers of 6mW and Q-switched (pulsed) operation with output in excess of 13W. Single-longitudinal-mode operation with a linewidth of 1.3MHz has been demonstrated, as has single-polarisation operation with an extinction ratio of 37dB. The extension of these techniques to operation at 1.55µm will find immediate applications in coherent communications system and will be discussed, as will additional active and passive devices including in-line fibre amplifiers and bistable fibre switches
Fabrication of Al<sub>2</sub>O<sub>3</sub> co-doped fibres by a solution-doping technique
No full textA new technique for fabricating optical fibres containing Al2O3 is described. Application of the technique to single-mode and rare-earth-doped fibres is discussed
Fabrication of optical fibres containing low levels of rare-earth ions
No full textFibres containing rare-earths have been produced with high absorption levels in the visible and near infra-red regions. This has been achieved without significantly compromising the low-loss characteristics at wavelengths between 900 and 1400 nm
Tunable single-mode fibre lasers
No full textRare-earth doped single-mode optical fibres have led to the development of a range of active fibre devices with numerous applications in telecommunications non-linear optics, spectroscopy and fibre sensors. These devices possess a number of advantages over their bulk counterparts. By virtue of their small active areas, very-low thresholds and high gains can be achieved and this has allowed the demonstration of lasing action on transitions never previously observed in glass. Since the typical fibre diameter is 125µm, thermal effects which plague bulk-glass lasers are minimal. Silica, the host material, has good power-handling characteristics; moreover, it broadens the rare-earth transitions, enabling highly tunable lasers at various wavelengths to be constructed. In this paper, the techniques for tuning fibre lasers are first discussed and the results obtained for different dopants and host glasses presented. Finally, the results obtained are critically compared and some suggestions for future directions are discussed
Optical Fibre Sensors - Chapter 8: Principles and Components
No full textOptical fibres have some degree of sensitivity to a wide range of external parameters. On the other hand the effects are usually small and are minimised as far as possible in fibres designed for telecommunications. Furthermore it is often difficult to differentiate between a number of small responses which may occur simultaneously. Considerable advantages can be gained in sensor applications by appropriate selection of core and cladding materials and by novel fibre structures and designs. Thus by spinning the preform during fibre drawing a high degree of circular birefringence can be introduced whilst the linear birefringence becomes negligible. Such fibres can behave as sensors of magnetic fields and electric currents. By introducing a high degree of linear birefringence fibre gyroscopes capable of measuring angular rotation become possible. The introduction of rare-earth materials into the core produces absorption bands with steep edges which have a strong wavelength sensitivity to changes in temperature. This produces the basis for distributed sensors which cover a wide range of temperatures. A variety of novel types of optical fibres are presently being explored for potential application to sensors and transducers
Self-imaging by ring-core fibers
No full textA tubular dielectric waveguide of typically 100 lambda diameter and single-moded wall-thickness can produce single or multiple images of one endface on the opposite one. Applications as single-mode N x N directional couplers are possible
Spectral variation of excited state absorption in neodymium doped fibre lasers
No full textThe spectral variation of gain and excited state absorption have been measured for neodymium doped silica fibres co-doped with germania and alumina. The results show that an observed excited state absorption peak at 1300 nm is considerably reduced in the alumina co-doped fiber
Fabrication of low-loss optical fibres containing rare-earth ions
No full textFibres containing rare-earth ions have been produced by an extended MCVD process. The fibres have very high absorption levels in the visible and near infra-red regions, without significantly compromising the low-loss characteristics of the fibre at wavelengths between 950 and 1400 nm
Thermal stress measurements in optical fibre preforms using preform profiling techniques
No full textAn analysis is presented of the effect of thermal stress on transverse refractive-index profiling of optical-fibre preforms. The theory leads to a new measurement technique for axial stress profiling
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