一种连续可变的光纤衰减器

本文从工作原理分析研究着手,设计制造了一种连续可变的光纤衰减器。该光纤衰减器性能稳定,精度高,适于光纤传输系统使用。     

Leaky optical fibre for large mode area singlemode operation

A novel optical fibre structure is introduced for large mode area singlemode operation. The fibre consists of a cladding index profile that increases monotonically in the radial direction. It is shown that the fibre can introduce exceedingly high leakage losses to the high-order modes, while maintaining a low loss to the fundamental mode. Numerical results are presented for power-law index profiles.     

Anomalous dispersion of new doubly clad optical fibre

The letter treats a doubly clad dielectric optical fibre. We assume that the core refractive index is greater than the outer-cladding refractive index, which is greater than the inner-cladding refractive index. This optical fibre, if properly designed, has an anomalous or negative normalised guide dispersion (?2/?)d2 ?/d?2 that compensates typical glass dispersion. Single-mode operation of this doubly clad fibre can be obtained with the core radius appreciably larger than that of a singly clad fibre with the same core and outer-cladding refractive indices.     

600 MHz optical signal transmission at the 3 ?m band using a fluoride optical fibre and a superconducting detector

We have demonstrated operation of a transmission system at the 3 ?m band. The system consists of a fluoride optical fibre, a superconducting BaPb1?xBixO3 (BPB) detector and a semiconductor Pb-salt diode laser. The low-level optical signal transmitted through the fibre is detected by the BPB detector up to 600 MHz. The observed results suggest that the BPB detector is suitable for use in infra-red optical transmission.     

Optical level equalisation based on gain saturation in fibreoptical parametric amplifier

Optical level equalisation operation based on gain saturation in an optical fibre parametric amplifier is reported. The signal output has been measured as a function of the signal input in a fibre parametric amplifier, with the result that the signal gain saturates as the input power increases and the output power reached a maximum value at a particular input level. Utilising this gain saturation property, optical level equalisation has been demonstrated     

Impact of pumping configuration on all-fibred femtosecond chirped pulse amplification

Ultrashort pulse fibre lasers have been investigated for many applications, such as medical imagery, microsurgery, micromachining and terahertz generation. These applications often require high peak power and short pulse duration at the same time. Such specifications are generally difficult to obtain directly from a laser oscillator without using external amplification. However, amplification has to be performed with care, mainly because nonlinear effects can deteriorate the pulse shape. This is particularly relevant in small core optical fibres where the signal is guided through a section of just a few square micrometres. To reduce the impact of nonlinear effects, one solution is to use chirped pulse amplification (CPA) [1, 2]. The CPA method consists of stretching the optical pulses before amplification so that the peak power is below the nonlinear effects threshold. Optical pulses are first stretched, then recompressed up to their original duration after an amplification stage. There are two main ways to recompress the pulses: by using a bulk optical grating or by means of an optical fibre. Indeed the use of bulk optical gratings is effective [3] but, in this case, the laser must include some free-space optics, then losing the advantage of an all-fibred, more stable and compact approach. On the other hand, the use of an optical fibre presents the inconvenience of a potential enhancement of nonlinear effects. Fibres with large mode area (LMA) including photonics crystal fibres (PCF) [4, 5] can be used in order to reduce the detrimental impact of nonlinear effects or to compensate for chromatic dispersion. However, in such a case, particular care has to be taken in the design and fabrication of the laser regarding multimode operation and splicing issues.     

Optical differential amplification in nonlinear fibre ring resonator

The theoretical basis and analytical expressions for the operation of a nonlinear fibre ring resonator as an optical differential amplifier are reported.<>     

Simultaneous amplification of wavelength-division-multiplexed signals by a highly efficient fibre Raman amplifier pumped by high-power semiconductor lasers

We describe the first operation of a high-power semiconductor-laser pumped fibre Raman amplifier (FRA) using high-Raman-gain optical fibre in the 1.5?m region. A high optical gain of 5 dB for 60mW of pump power is obtained. We have also achieved simultaneous amplification of wavelength-division-multiplexed signals by the FRA.     

New coupling method for GaAs-laser?fibre coupling

A new method for coupling a diode laser to an optical fibre is described. This uses a cylindrical glass fibre as a focusing element. Optical feedback from the fibre endface has been found to have an influence on the laser output power. As a result, the light power launched into a single-mode fibre was higher than that obtainable from the laser during normal operation.     

野战光缆通信的微机监控分系统

野战光缆通信是现代军事通信的一种重要手段,它对设备的可靠性、机动灵活性、功耗、操作等方面有着相当严格的要求。基于这些实际需要,本文介绍一种高可靠、低功耗、易于操作的微机监控分系统。     

Reading light-optoelectronics on indium phosphide

In the future every house could be served by a single optical fibre which will carry basic telephony plus a wide range of broadband services such as video, videophone and high definition TV. The author discusses optoelectronic circuits (OEIC) as cheap optical receiver components. The construction and operation of OEIC are described and the use of them in optical receivers is discussed     

Emission frequency stability in single-mode-fibre optical feedback controlled semiconductor lasers

A newly designed semiconductor laser emitter with adjustable linewidth by controlling the coupling to a single-mode fibre is described with emphasis on thermal requirements to obtain a high-frequency stability. A stable operation has been achieved during more than 1 h using an AlGaAs laser diode with optical feedback from a 50 cm-long single-mode fibre resulting in a 50-fold reduction of the spectral linewidth.     

Simplified optical-fibre breaking machine

A machine has been designed and constructed to prepare the ends of optical fibres prior to jointing. It is intended to be simple in operation, while maintaining accurately controlled breaking conditions to ensure that mirror-finished fibre ends are made with complete reliability.     

High-speed characteristics at high input optical power of GaInAsPelectroabsorption modulators

High-speed characteristics at high input optical power levels of GaInAsP double heterostructure electroabsorption modulators are investigated. It is shown that the bandwidth degradation due to high input optical power is strongly dependent on the absorption coefficient. A design to maintain high-speed characteristics under milliwatt range output power operation, and experimental results including a 100 km single-mode fibre pulse transmission experiment are demonstrated     

Application of UV laser induced Ge-oxygen defect fluorescence for fibre characterisation

A new technique to monitor germanium oxygen deficiency centre defects (GeODC) and their relation to the refractive index profile in Ge-Si optical fibre have been developed. This method is based on UV excited luminescence of GeODC in silica based optical fibres. The GeODC defect profiles are unique to the fibre refractive index (profile of GeO₂) and method of fibre making.     

1.2 Gbit/s, 52.5 km optical fibre transmission experiment usingOEICs on GaAs-on-InP heterostructure

High-performance, long-wavelength OEICs on a GaAs-on-InP heterostructure were fabricated. For the transmitter OEIC, high-speed operation up to 2.4 Gbit/s was achieved, and a receiver sensitivity as high as -26.0 dBm for a 1.2 Gbit/s NRZ signal was realised for the receiver OEIC. To confirm the usefulness of these OEICs for optical fibre networks, a 1.2 Gbit/s optical fibre transmission experiment was successfully carried out over a 52.5 km span     

Tunable 4/spl times/10 GHz optically modelocked semiconductor fibre laser

A wavelength-tunable 4/spl times/10 GHz optically modelocked semiconductor fibre ring laser is demonstrated. A semiconductor optical amplifier (SOA) is used as a gain medium and optically controlled mode-locking element, in addition to four superimposed linearly chirped fibre Bragg gratings to provide tunable, multi-wavelength operation. The four wavelengths can be tuned simultaneously with constant wavelength separation by changing the modulation frequency.     

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。     

Experimental 1.5 μm coherent optical fibre transmission systems

The authors consider the design requirements for 1.52 μm coherent optical fibre transmission systems. Some of the essential requirements are: narrow linewidth sources, polarisation stable transmission media, low insertion loss optical mixers and frequency tracking or phase locked local oscillators. Having been successful in reducing the linewidth of semiconductor lasers to less than 30 kHz, by using injection locking techniques, and in fabricating optical mixers with insertion losses of the order of dB, they have been able to experiment with coherent optical fibre transmission systems to assess their practicability. In this paper it will be shown that coherent systems can be operated over long lengths of conventional low loss monomode fibre without any polarisation penalty and give far better performance than direct detection systems.     

Rocking filter formation in photosensitive high birefringence optical fibres

Parent et al. (1985) observed that the refractive index changes induced in optical fibres by Hill grating formation (at 488 and 514-5 nm) were birefringent. A wavelength filter, formed in a simple and novel way by exposing high birefringence fibre to linearly polarised 488 nm light, is reported. Narrow bandwidth operation and high conversion efficiencies are achieved experimentally between the two orthogonal polarisation states of the fibre.<>