Showing papers by "Laurence Reekie published in 1989"

Efficient pump wavelengths of erbium-doped fibre optical amplifier

Abstract: By choosing pump wavelengths at which excited state absorption does not occur, efficient high gain operation of erbium-doped fibre amplifiers is possible. Practical pump wavelengths of 532nm and 980nm are identified as optimal, giving gains as high as 1.35 dB/mW and 2.2 dB/mW of pump at the two wavelengths, respectively.

Er/sup 3+/-Yb/sup 3+/ and Er/sup 3+/ doped fiber lasers

Abstract: Single-mode fiber lasers operating at approximately 1.57 mu m are described. Output powers of >2 mW are reported for laser diode pumped operation. Direct comparison is made between fiber lasers using sensitized erbium (Er/sup 3+/ and Yb/sup 3+/) and erbium on its own. The performance of Er/sup 3+/-Yb/sup 3+/ fiber lasers is analyzed in more detail as a function of fiber length. Both CW and Q-switched operations are studied and the results obtained demonstrate that practical sources at 1.5 mu m are available from diode pumped Er/sup 3+/-Yb/sup 3+/ systems. >

Multichannel crosstalk and pump noise characterisation of Er3+-doped fibre amplifier pumped at 980 nm

Abstract: It is shown that as a consequence of the long fluorescence lifetime in an Er/sup 3+/-doped fibre amplifier, interchannel crosstalk and pump-noise breakthrough are minimal for modulation frequencies >100 kHz.

High-quantum-efficiency Er(3+) fiber lasers pumped at 980 nm.

Abstract: Significant improvements in the operation of Er(3+)-doped silica fiber lasers operating at wavelengths between 1.5 and 1.6 microm are reported. The use of 980 nm as the pump wavelength provides an output that is limited mainly by the quantum efficiency of the lasing process. It is thus considerably more efficient than previous results using ~810-nm pumping, where excited-state absorption degrades the lasing performance. Operation at three discrete output wavelengths is observed and is accounted for by studying gain across the lasing bandwidth.

Application-Specific Optical Fibres Manufactured from Multicomponent Glasses.

Abstract: Silica has been mostly used in special fibres because of its low loss transmission. However, some special fibres require short lengths for optimum performance. Among these are current sensors where the bandwidth is an important criterion, most nonlinear optical devices and rare-earth doped fibre lasers. Here, materials with properties optimized for short lengths of a few metres are favoured. These are typically multicomponent compound glasses. The composition of these glasses can be tailored to the application intended. By use of established glass melting, glass forming and fibre fabrication techniques, all optical devices can be made compatible with conventional monomode silica-based fibres. We have fabricated optical fibres from both commercially available and new component glass melts. Fibres with losses close to the intrinsic loss of the bulk glass precursors are obtainable using a rod-in-tube technique. The intrinsic loss is generally two orders of magnitude larger than silica. The objective of this presentation is to demonstrate the potential and practicality of using compound glass fibres for application in nonlinear devices, fibre sensors and fibre lasers.

Single polarisation fibre lasers using an integral polariser

Abstract: Fibre lasers represent a new class of active fibre devices with considerable potential for use in telecommunications, sensors and laboratory measurements For these applications the realisation of a practical single-polarisation single-mode (SPSM) fibre laser is of considerable interest In this paper we report an integral fibre polariser technique for making SPSM fibre lasers The corresponding theory, design method and experimental results are also presented It is shown that it is far more efficient to use an intra-cavity polariser than to polarise the output light with an external polariser

Multichannel crosstalk and pump noise in an Er3+-doped fibre amplifier pumped at 980nm

Abstract: Er3+-doped single-mode fibre amplifiers operating around 1.54µm are emerging as promising contenders for use in future high bit-rate long-haul communication systems. They have the advantage over semiconductor amplifiers of being wholly compatible with telecommunications fibre, thus eliminating both splice loss and end-face reflections which would be detrimental to amplifier performance, and are polarisation-independent. Fibre-to-fibre gains in excess of 34dB have been demonstrated with excellent saturation and noise performance. However, as with all optical amplifiers, noise on the pump (injection current or optical wave), will feed through to the amplified signal. In addition, owing to homogeneous broadening, competition for the available gain between two amplified channels closely-spaced in wavelength leads to inter-channel modulation in an ASK system. We show here that the very long fluorescent time-constant in Er3+ (tau = 14ms, cf 1ns for semiconductor amplifiers) suppresses these effects by >40dB at frequencies >100kHz, thus providing a further advantage for this type of amplifier