Rugged all-fibre endless polarisation controller

A polarisation controller comprising four lengths of PM fibre wound onto piezoelectric cylinders has been produced. It is mechanically rugged, has an insertion loss of 1.5 dB, and is capable of endless control between two arbitrary time-varying states of polarisation. Polarisation control has been successfully demonstrated for the first time in a coherent optical transmission system over installed fibre     

Endless polarisation control in coherent optical communications

An endless polarisation control system is presented which transforms a given state of polarisation (SOP) into any desired one. It features four birefringent SOP control devices of only two different types. A microprocessor-based system in a heterodyne experiment confirms the theory.     

Feasibility study on common polarisation control for coherent FDM transmission system

A common polarisation control with a single polarisation controller for a coherent optical FDM transmission system is proposed. This scheme is applicable to the system carrying 600 Mbit/s-16 channel to 5 Gbit/s-2-channel coherent FDM signals, with a great reduction in receiver complexity.<>     

565 Mbit/s optical PSK transmission system with endlesspolarisation control

A 565 Mbit/s optical PSK transmission system incorporating automatic endless polarisation control is reported. A receiver sensitivity of -49.8 dBm was achieved, and the randomly varying polarisation state of the received signal was tracked with no observed degradation in system performance     

Polarisation-scrambled Er-doped superfluorescent fibre source with improved mean-wavelength stability

A polarisation scrambling scheme is employed to reduce the pump-polarisation-dependent mean-wavelength change in the Er-doped superfluorescent fibre source for gyroscope application. A PZT-based fibre-optic polarisation modulation is used at the pump port for polarisation scrambling. Changes of mean wavelength owing to pump polarisation variation are suppressed below 1 ppm.     

Stress effect for polarisation control of surface emitting lasers

To control the electric polarisation of output light in surface emitting (SE) lasers, the stress effect on the resonance model of SE lasers with an elliptical holed region is investigated. For the first time, polarisation switching by external stress has been observed and the relation between the polarisation characteristics and the structural dependence on stress clarified.<>     

Multichannel frequency conversion experiment using fibre four-wave mixing

Multichannel frequency conversion is demonstrated using four-wave mixing. A polarisation independent configuration is employed, by which polarisation control for each signal is not necessary. By setting the pump light frequency at the zero-dispersion wavelength of the fibre, three FSK modulated signals with a frequency spacing of 70 GHz are simultaneously converted with an equal efficiency of -27.5 dB. Bit error rate measurements confirm the feasibility of this conversion scheme.<>     

Quadrature phase sampling of a fibre interferometer by input-polarisation switching

A technique for the generation of quadrature phase components at the output of a fibre interferometer using input polarisation modulation is described. This approach allows a passive path-balanced sensor interferometer to be remotely interrogated using a simple concept based on polarisation switching of the input state of polarisation coupled to the interferometer.<>     

基于嵌入式技术的激光偏振度测量系统

为提升激光偏振度测量的精度与时效性,设计基于嵌入式技术的激光偏振度测量系统,其包括探测、控制器与上位机3部分,通过探测部分接收激光器发射的激光并通过两个液晶可变相位延迟器(LCVR),抵达偏振分光棱镜后分为两束偏振光,采用探测器探测两束光的光强传输到控制器部分;由控制器部分的嵌入式信号处理模块对所接收光强实施处理与转换后,传给AVR单片机,AVR单片机一边将转换后数字信号经串口送至上位机,由上位机内嵌入式软件和计算机操控软件运算出激光偏振度等参数并呈现运算结果,另一边经D/A产生可控制LCVR液晶相位延迟量的方波信号,继续测量其余待测激光偏振度。结果表明,该系统具有较高的测量精度,测量结果稳定性高,可实现对信号的同步实时传输,传输性能稳定,可有效促进系统的测量时效性。     

Polarisation guiding in ultralong distance soliton transmission

Signal polarisation rotation due to polarisation dependent loss has been observed for the first time in an optical communications transmission system. In particular its effect as a limiting factor in solitonic polarisation multiplexed systems is discussed. An analytic expression for the degree of rotation is presented and experimentally verified. Additionally, 5 Gbit/s solitons have been transmitted a distance of 11000 km without transmission control     

Reconfigurable microstrip antenna with polarisation diversity

A single probe-fed reconfigurable microstrip patch antenna with symmetric cross slots is proposed. By controlling four pin diodes on the patch slots, the proposed antenna has right hand circular polarisation, left hand circular polarisation or linear polarisation.     

New fabrication technique for high performance polarisationmaintaining optical fibre couplers

A simple and novel technique for fabricating polarisation maintaining optical fibre couplers is reported. This technique is different from existing approaches of polarisation coupler fabrication, in that it avoids the need to align the polarisation axis during each coupler fabrication. Both low loss and low polarisation crosstalk have been achieved     

Four-port homodyne receiver for optical fibre communications comprising phase and polarisation diversities

A new four-port homodyne receiver for optical fibre communications is proposed and studied experimentally. It comprises phase-and polarisation-diversity schemes, removing the need for phase locking and polarisation control. The bit-error-rate measurement is also reported.     

Monomode fibre polarisation scrambler

A technique for the pseudodepolarisation of a long-coherence-length source is described, which is based on a simple polarisation modulation scheme. Using a length of high-birefringence fibre wound on to a piezoelectric transducer, a simple all-fibre polarisation scrambler can be constructed.     

Passive integrated optical polarisation mode-splitter in lithium niobate employing a resonant metal-loaded structure

A passive polarisation mode-splitter has been demonstrated in Z-cut Y-propagating LiNbO/sub 3/ which achieves polarisation crosstalk better than -30 dB and excess loss of less than 1 dB in both polarisation states at lambda =1.52 mu m. The technique employed simplifies the design of polarisation mode splitters for arbitrary operating wavelengths and LiNbO/sub 3/ wafer orientations.<>     

Endless polarisation control experiment with three elements of limited birefringence range

An automatic endless polarisation control system is presented. A computer controls three birefringent elements and applies simple reset strategies at the range limits.     

Passive depolariser based on artificial polarisation-dependent delay

A passive depolariser based on artificial polarisation-dependent delay is demonstrated. Experimental results show that a low degree of polarisation (<2%) and a low polarisation-dependent loss (0.08 dB) are obtained for any input state of polarisation.     

Optical polarisation control utilising an optical heterodyne detection scheme

An optical polarisation control scheme utilising optical heterodyne detection for coherent transmission is proposed and demonstrated at a wavelength of 1.5 ?m. It converts an arbitrary polarisation state to a linear state at a received optical power level of less than ?70 dBm.     

Polarisation insensitive wavelength conversion using a lightinjected DFB-LD with a loop configuration

A configuration is proposed for polarisation insensitive wavelength conversion using an oscillating LD. By employing a loop with a polarisation beamsplitter, an optical signal is always injected into an LD in the TE mode irrespective of its polarisation state. An experiment using an MQW DFB-LD demonstrates the operation for a 4.5 Gbit/s signal     

40 Gbit/s OTDM soliton transmission over transoceanic distances

40 Gbit/s soliton transmission is achieved in a recirculating loop over 10000 km, for the first time to the authors' knowledge. With a single carrier wavelength. Propagation has been tested with and without polarisation multiplexing thanks to low polarisation dependency electroabsorption modulators for in-line control and for the time demultiplexing receiver