摘要:

We review experimental and theoretical work on the effects of the Kerr nonlinearity in optical fibres. The nonlinear Schrödinger equation is introduced and its solutions are discussed. The effects of perturbations both to the initial pulse and to the equation demonstrate the stability of solitons. Applications of this work include pulse compression and the soliton laser. Finally we discuss recent work on the modification of the linear guiding properties at high intensities.

DOI:10.1049/ip-j.1987.0025

出版商:IEE    

年代:1987

数据来源: IET

摘要:

From the exact two-soliton solution and through numerical studies, three schemes of minimising soliton interaction are compared in detail, in particular, amplitude shifting the adjacent solitons, phase shifting, and the use of the higher-order dispersion of the fibre. It is shown that amplitude shifting is the most desirable scheme, in terms of maximising the bandwidth of the nonlinear fibre and in terms of simplicity and stability.

DOI:10.1049/ip-j.1987.0026

出版商:IEE    

年代:1987

数据来源: IET

摘要:

The propagation of strongly nonlinear TM surface-guided waves in media controlled by a self-focusing third-order optical, unsaturated nonlinearity is analysed theoretically. In this theory both the amplitude and the wave number of the guided wave are power dependent. The reasons for studying these waves are explained and it is emphasised that strong nonlinearity can lead to a number of device applications. Although such devices are not simulated here, a number of planar structures that are of potential device interest are discussed. A mathematical theory is presented that is both free of previous approximations and capable of dealing with many types of nonlinear mechanisms. The waveguide structures that are considered are a single interface between semi-infinite linear and nonlinear media, a linear guide symmetrically bounded by self-focusing nonlinear media and two linear waveguides coupled through a nonlinear medium. The exact theory quickly leads to equations that can only be solved numerically but some degree of analytical progress is reported here for the single-interface case. Two methods of solution are presented, one based on the first integral of the nonlinear wave equation and the other based on a spline collocation numerical method. Full numerical results are given in the form of power variation with effective wave index and a number of sample field distributions. The results are especially interesting in connection with the structures that possess negative dielectric components and the superwaves of the nonlinearly coupled guides. In the former, maxima, minima and negative power regions arise. In the latter, for a critical coupling distance, there exists a region of guide index for which the power flow down the guide is approximately constant

DOI:10.1049/ip-j.1987.0027

出版商:IEE    

年代:1987

数据来源: IET

摘要:

We have observed stimulated Raman scattering and nonlinear enhanced pulse broadening at 1.32 μm. We used two monomode optical fibres with zero-dispersion wavelengths of 1.28 and 1.55 μm. This enabled us to observe the effect of dispersion on the interaction length for Raman scattering.

DOI:10.1049/ip-j.1987.0028

出版商:IEE    

年代:1987

数据来源: IET

摘要:

An investigation of the spectral and temporal characteristics of the self-phase modulated pulses exiting from a germania-doped fused-silica-core single-mode optical fibre has been undertaken at 1.064 μm. For peak powers below the stimulated Raman scattering threshold the spectral data were in excellent agreement with a simple theory developed for negligible fibre group-velocity dispersion and symmetrical chirp-free input pulses. For elevated peak-power levels a complementary study of the temporal and spectral features of the first-order Stokes Raman and pump pulses has been carried out. It was observed that the onset of stimulated Raman scattering leads to both spectral and temporal pump-pulse asymmetry and hence to deviation from the theoretical spectral predictions. In addition, a simple fibre Raman oscillator was constructed and its characteristics are described in some detail.

DOI:10.1049/ip-j.1987.0029

出版商:IEE    

年代:1987

数据来源: IET

摘要:

Two pulse-shortening schemes based on the nonlinear propagation of picosecond pulses from a Nd: YAG laser in single-mode optical fibres are described. In the first experiment, a spectral-windowing technique was employed to compress self-phase modulated pulses exiting 100 m of optical fibre, and compression factors of 2.5 were recorded in good agreement with theoretical predictions. The technique was adapted to enable the time-dependent frequency shift occurring after pulse propagation through 2 km of fibre to be measured. In the second experiment, cascaded stimulated Raman generation, occurring when a high-power pump pulse propagated in 4 m of fibre, was studied. Lower-order components in the cascade were severely depleted through generation of higher-order Stokes signals, leaving negatively chirped pulse fragments. These were compressed with a dispersion-tunable Gires-Tournois interferometer and compression ratios of times 4 were obtained.

DOI:10.1049/ip-j.1987.0030

出版商:IEE    

年代:1987

数据来源: IET

摘要:

An experimental investigation of nonlinear power transmission limits in short lengths of single-mode fibre is described. Nonlinearities have been observed at peak optical power levels of a few hundred watts, and these thresholds have been compared with theoretical predictions. The consequences of these power transmission limits for the development and characterisation of nonlinear fibre waveguide devices are discussed.

DOI:10.1049/ip-j.1987.0031

出版商:IEE    

年代:1987

数据来源: IET

摘要:

Recent studies of monomode silica fibre which has rare-earth impurity ions incorporated into the core region have shown that it can exhibit laser action with low threshold and high efficiency when end pumped by an external laser source. In the paper we describe the first demonstration ofQ-switching of the4F3/2-4I9/2Nd3+transition at 0.9 μm using a fibre laser of this type. A birefringent filter has been used to tune the laser output over the range 0.900–0.945 μm. We also report on the performance of the laser at 1.08 μm under conditions ofQ-switching and active mode-locking. InQ-switched operation an intracavity acousto-optic modulator was used to generate pulses of 200 ns duration and 8.8 W peak power at repetition rates up to 1 kHz. Active mode-locking of the fibre was accomplished using acousto-optic modulation of the cavity losses at 41.4 MHz, converting the laser output to a train of pulses of subnanosecond duration.

DOI:10.1049/ip-j.1987.0032

出版商:IEE    

年代:1987

数据来源: IET

摘要:

A convenient source of high-power (~20 kW) stable mode-locked pulses at 1.54 μm, suitable for pulse-compression studies in the negative group-velocity-dispersion region of optical fibres, is described. The source is based on a capillary-waveguide Raman laser, using CH4gas, and pumped by a mode-lockedQ-switched CW Nd:YAG laser. Initial results for a synchronously pumped Raman laser are also presented.

DOI:10.1049/ip-j.1987.0033

出版商:IEE    

年代:1987

数据来源: IET

摘要:

The fabrication of successive tapered coaxial couplers is investigated as a means for producing all-fibre wavelength filters. Narrow-band filters are reported from a cascade of tapered coaxial couplers of broad wavelength response.

DOI:10.1049/ip-j.1987.0034

出版商:IEE    

年代:1987

数据来源: IET