Location of imperfections in optical glass-fibre waveguides

An echo-pulse technique for the location of fibre imperfections is described. The technique has been successfully applied to a plastics-coated Selfoc fibre and a plastics-coated silica-based fibre. Both showed a break. In the Selfoc fibre, an additional fibre defect was located. The same method may be used to measure rapidly the fibre length.     

Experimental demonstration of step-like dispersion profiling inoptical fibre for soliton pulse generation and compression

Generation of 100 GHz trains of 500-700 fs pulses using dual-frequency beat conversion in a step-like dispersion profiled fibre is reported. The authors believe that this is the first time the generation and compression of soliton pulses using such a fibre has been demonstrated. The fabrication of such fibre assemblies does not require any special facilities and relies only on conventional optical fibre technology. They believe that the use of profiling the fibre dispersion by fibre segments instead of continuously dispersion-decreasing fibre is not only possible but preferable in many applications     

Cost-reduced Cable Delivery for the 21st Century

This paper addresses the issue of cost-effective optical fibre cable delivery within current projections of fibre build. The implications are generally valid for fibre to the home (FTTH), but additional considerations will apply. The challenge lies in increasing the penetration of optical fibre for business customers and addressing the impending exhaustion of core network fibre.     

特种人造纤维微观结构的扫描电镜观察和研究

本文以吸湿睛纶、双层纤维，中空纤维，酚醛纤维和阻燃纤维等特种人造纤维为研究对象，用扫描电子显微镜观察和研究了它们各自的微观形态，结构特点和性能。提出了一些认识，以便为纺织业和印染业的生产工艺提供可靠的科学依据。     

In-situ investigation of coupling between a fibre and a slab waveguide

The mode coupling between a fibre and a slab waveguide was experimentally investigated during the formation of the slab. A thin film has been deposited on a polished fibre close to the core-clad interface. By monitoring the optical transmittance of the fibre during the film deposition the coupling efficiency between the formed slab and the fibre has been studied as a function of the film thickness. Strong attenuation in the fibre output has been observed for thickness values at which the propagation constants of the optical mode in the fibre match those of the slab waveguide.<>     

Novel fibre optic gyroscope with a configuration combining Sagnac interferometer with fibre ring resonator

A novel fibre optic gyroscope, with a structure making use of the combination of a Sagnac interferometer with an active fibre ring-resonator, is proposed and analysed. The proposed gyroscope can be viewed as a generalised structure of the conventional Sagnac interferometric type fibre optical gyroscope. It has the advantages of both long fibre loop length and multipath interferences. By inserting a fibre amplifier in the loop to provide an optical gain of several dB, the relative maximum sensitivity is enhanced to approximately 30 times more than that of conventional Sagnac interferometric fibre optic gyroscopes.<>     

Forced pump oscillation at anti-Stokes wavelength of coupled Raman fibre laser resonators

Multi-watt oscillation of a Yb/sup 3+/-doped silica fibre pump laser is demonstrated at two wavelengths when pump-coupled Raman fibre laser resonators are constructed using fibre end reflection and a dielectric mirror, which are common to both the pump and Raman fibre lasers. Using an off-resonant Bragg grating to force the initial oscillation of the Raman fibre laser, pump emission at the anti-Stokes wavelength is demonstrated.     

单模光纤耦合器技术现状及应用

本文扼要介绍了单模光纤耦合器的技术现状和发展动态;概述了我所引进的世界一流水平的美国 Aster 公司单模光纤耦合器制造技术;简单介绍了单模光纤耦合器在光纤通信、光纤传感和尤纤仪器仪表方面的应用。     

Fibre-polarimeter based on grating taps

The fabrication of novel tilted fibre Bragg gratings coupling light out of the fibre core into two different directions is demonstrated. These gratings in combination with a fibre based quarter waveplate are used to form a high-speed fibre polarimeter for real-time polarisation monitoring.     

声光技术在光纤系统中的应用

本文简要介绍了在光纤通信、光纤传感和光纤信号处理枝术等各种光纤系统中可能开发应用的固体声光技术和光纤声光技术。     

长周期莫尔光栅的理论研究

长周期光纤光栅作为一种损耗型的带阻滤波器，在光纤通信和光纤传感器领域有着广泛的应用。结合长周期光纤光栅的传输特性，利用传输矩阵法对多种长周期莫尔光栅的透射谱进行了理论模拟。分析结果表明，莫尔光栅技术在制作高性能的相移长周期光栅和变迹长周期光栅上有着很好的应用前景。     

Enhanced tuning mechanism in fibre laser based on multimode interference effects

A 12 nm tunable fibre laser is demonstrated. The tuning mechanism uses an SU-8 fibre gripper for automatic alignment of a multimode fibre and gold-coated fibre (facet) mirror. Wavelength tuning is achieved using the wavelength dependent re-imaging effect that occurs in multimode fibres     

Measurement of fibre-optic chromatic dispersion from RIN spectra of a tunable fibre laser

The chromatic dispersion of optical fibre is determined from the wavelength dependence of the mode spacing of the fibre laser with and without the intracavity test fibre. This approach is particularly useful for characterising the dispersion of modelocked fibre lasers, where control of the total laser dispersion is required.<>     

Optical-fibre waveguide with a single-crystal core

Some properties of a new single-crystal optical fibre are described. The fibre is constructed with the nonlinear optical crystal meta-nitroaniline as its core. In its present configuration, the fibre acts as an effective polariser. Alternative configurations may yield a number of electro-optic fibre devices.     

Fibre probe far-field technique for mode-field diameter measurementof single-mode fibres

A far-field pattern (FFP) technique using an optical fibre probe to measure the mode-field diameters of single-mode fibres is described. The endface separation between the test fibre and the probe fibre can be reduced to a tenth of the fibre/detector separation in the conventional scanning detector method     

Multiwavelength erbium-doped fibre laser based on ahigh-birefringence fibre loop mirror

A novel multiwavelength fibre laser is proposed, which is based on a fibre loop mirror formed by a high-birefringence (HiBi) fibre, a polarisation controller, and a directional coupler. By setting the polarisation controller properly, the HiBi fibre loop mirror acts as a polarisation-independent wavelength filter. With this configuration, the wavelength spacing of the laser can be varied accurately by adjusting the length of the HiBi fibre. Experimentally, by cooling the erbium-doped fibre with liquid nitrogen to reduce its homogeneous linewidth, stable emission at 16 wavelengths with a spacing of 0.8 nm and an amplitude variation of <5 dB was achieved     

浅论纯二氧化硅纤芯光纤和PICVD工艺

本文对纯二氧化硅纤芯的 PICVD 光纤及 PICVD 工艺作了简要评述。这种纯二氧化硅纤芯的 PICVD 光纤有较宽广的低损耗皮长区,尤其是其在通常的短波长波段(860nm)有着极低损耗:1.3dB/km,优良的抗辐照性能。其单模光纤也可能有较宽广的低色散区域。文章指出了这种光纤的出现可能会大大加速光纤技术应用的推广,并使光纤技术再发展获得新的动力。     

PMD指标对光纤的影响

随着光纤系统的改进及未来通信系统剧增的需要，长距离，多信道，高数据率光纤系统的运用越来越普及，光纤偏振模散（PMD）的影响也越来越显著，就光纤的PMD指标进行论述，为光纤系统设计，提高光纤系统性能，把PMD纳入系统设计考虑之列年代一种方法。     

Graded-index-type crystalline fibre for IR light transmission

A new method for making a graded-index-type crystalline fibre is proposed. A fibre for IR light transmission with crystalline claddings was desired for improving the reliability of the crystallinc fibre and for avoiding any excess loss at the core surface. A fibre with the core-cladding structure was made by complex extrusion with KRS-5 as the core and KRS-6 as the cladding. Obtaining a smooth core-cladding interface was very difficult. This problem was overcome by a diffusion of composite ions by annealing after the extrusion. The fibre has a concentration distribution that can be accounted for by a GI fibre. The transmission loss of the CO2 laser is 0.2 dB/m with a launching NA of 0.05.     

Mitigating the risk of high power damage to the BT network

Optical powers used in optical telecommunications networks have increased over time with the advent of technologies such as erbium doped fibre amplifiers, dense WDM, and fibre Raman amplifiers. Erbium fibre and Raman amplifiers with output powers up to 1 W and 2 W respectively are now available for deployment giving optical power densities of ≈14 000 MW/m² per Watt launched into a single mode fibre. This compares with 74 MW/m² for the surface of the sun. It is thus essential to ensure that the risk of optical damage to the fibre is understood and steps are taken to mitigate it where necessary. Research carried out by BT over the last few years has shown that fibres carrying relatively modest optical powers, as low as 200 mW for the most sensitive fibres, can be catastrophically damaged at tight fibre bends. Damage is caused by some of the optical power lost at the bend being absorbed by the fibre coating that may over time lead to a sudden increase in temperature to over 700 °C causing either the silica to kink mimicking a fibre break, or the coating to burn off at the bend leading to fibre failure on subsequent handling. This paper describes factors that increase the risk of short-term catastrophic damage at fibre bends, presents experimental results to show the variation in sensitivity between different fibres, and discusses new important theoretical results modelling the temperature rise in the fibre.