Polarisation-mode dispersion monitoring technique based onpolarisation scrambling

A simple technique that could be used to monitor the first-order polarisation-mode dispersion in wavelength-division multiplexed networks is proposed. This technique, based on the polarisation scrambling, could measure the polarisation-mode dispersion with accuracy of ±2 picoseconds even with the existence of large chromatic dispersion     

PMD and PDL monitoring of traffic-carrying transatlantic fibre-optic system

For the first time the direct monitoring of polarisation mode dispersion (PMD) and polarisation-dependent loss (PDL) in a traffic-carrying transatlantic fibre-optic system without the requirement of loopingback is reported. The impact of transmitter polarisation scrambling in the measured results is analysed and verified by the measured results.     

Spin controlled optically pumped vertical cavity surface emitting laser

It is shown that the output polarisation of optically pumped vertical cavity surface emitting lasers (VCSELs) can be unambiguously controlled by the pump polarisation. The degree of the output polarisation is higher than that of the pump polarisation. It is concluded that the polarisation of VCSELs with spin polarised electrical pumping can be controlled even with low spin injection efficiencies.     

BER fluctuation suppression in optical in-line amplifier systemsusing polarisation scrambling technique

The effectiveness of the polarisation scrambling technique for suppressing BER fluctuation is confirmed experimentally with a 2900 km optical in-line amplifier transmission system. The technique suppresses the BER fluctuation by three orders of magnitude, from 10^-5-10^-9 to 10^-810^-9     

2.5 Gbit/s-9720 km, 10 Gbit/s-6480 km transmission in the FSAcommercial system with 90 km spaced optical amplifier repeaters anddispersion-managed cables

The authors report 2.5 and 10 Gbit/s transoceanic distance transmission in a commercial FSA optical amplifier system which has 90 km repeater spacing. The unique fibre dispersion management technique and amplifier passband management scheme used in the system are successfully demonstrated. The SNR improvement achieved with polarisation scrambling is also reported     

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.<>     

Fibre optical parametric amplifiers with circularly-polarised pumps

A fibre optical parametric amplifier with orthogonal circularly-polarised pumps requires only half the pump power of an amplifier with linearly-polarised pumps to achieve a given gain. The gain is also independent of the polarisation of the input signal.     

Suppression of polarisation-induced signal fluctuation in optic distributed sensing system based on stimulated Brillouin scattering

A new scheme capable of suppressing polarisation sensitivity in the Brillouin optical time domain analysis distributed sensing system is demonstrated. The polarisation-induced signal fluctuation is suppressed from >+300 μϵ(which causes measurement to fail) to +50 μϵ by introducing a cost-effective polarisation diversity scheme on the pump light. Stable distributed strain measurement along a 1.2 km singlemode fibre is achieved. This scheme needs no active component and the strain measurement time is only 3s.     

Depolarised broadband source generated by hybrid effects of Raman scattering, parametric process and erbium-doped superfluorescent

A depolarised high power (200 mW) broadband source (1520-1620 nm) with high polarisation stability is obtained using a single pump based on the hybrid effects of dual-order Raman scattering, parametric process in highly nonlinear fibre and erbium-doped superfluorescent.     

Er-doped superfluorescent fibre source with enhanced mean-wavelength stability using chirped fibre grating

An Er-doped superfluorescent fibre source with enhanced mean-wavelength stability 2 ppm over the 0degC to 70degC range using chirped fibre grating is demonstrated. The effects of the temperature of the fibre, the pump power, the pump wavelength, the pump state of polarisation, and the feedback power have been considered and minimised with corresponding techniques.     

Polarization properties of stimulated Brillouin scattering insingle-mode fibers

The polarization properties of stimulated brillouin scattering (SBS) in low birefringent optical fibers were evaluated using Stokes calculus. It was found that the Brillouin gain for orthogonally polarized pump and probe wave is half (in dB) of the gain for identical polarization, and not equal as often mentioned in literature. Therefore the polarization factor is K=1_1/2 for complete polarization scrambling, and not K=2. The spontaneous SBS has the same state of polarization as the pump, and its degree of polarization is 33.3% for low pump powers and near 100% for high pump powers. The experimental results agree very well with the calculations     

WCDMA网络扰码规划的研究

扰码规划是WCDMA网络规划的一部分,本文对WCDMA扰码规划的原理进行了阐述,分析了小区搜索、扰码规划的不同方案和需要注意的扰码复用距离问题。良好的扰码规划对于获得最优的网络性能很重要,在进行扰码规划的时候,要结合实际的网络情况,选择合理的扰码复用距离和邻区扰码组的分配,以达到最好的网络性能的效果。     

Theoretical analysis of polarisation-insensitive wavelength conversion by four-wave mixing in photonic crystal fibre

Polarisation-insensitive wavelength conversion by four-wave mixing (FWM) has been demonstrated in a 20 m short nonlinear photonics crystal fibre. Theoretical analysis confirms that the combination of a 45deg pump launch and a minimum pump-probe detuning is required to reduce the polarisation sensitivity of FWM to ~1 dB.     

A voice scrambler for mobile communication

A new voice scrambling method for mobile communication is proposed. The principle is to invert the voice sample polarity selectively according to the scrambling code, smooth it with a low-pass filter, and feed it to the radio transmitter. To utilize the principle, the necessary techniques such as filtering, synchronizing and scrambling code design, are described. The whitened spectrum of the scrambled voice and a large number of key codes provide a high security communication. The scrambler presented here is designed for an adaptor to press-to-talk mobile radio. Voice spectrum variation by scrambling is demonstrated and articulation is measured under nonfading and fading conditions with signal to noise (S/N) variation. Those results show that the scrambling method is suitable for mobile communication with rapid synchronization for press-to-talk radio, noise, and fading immunity.     

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     

彩色图像置乱方法研究

这里主要研究彩色图像的置乱方法,目的是提高置乱效果及置乱效率。分别研究了基于像素灰度变换的彩色图像置乱方法及基于像素位置变换的彩色图像置乱方法,仿真分析了2种置乱方法的不足,提出了一种新的基于Arnold变换的彩色图像置乱方法。采用同时改变像素位置及灰度值的方法,兼顾了置乱图像在视觉上及理论上的置乱效果。仿真实验表明该置乱算法提高了置乱度,节约了恢复时间,是一种简单、高效的彩色图像置乱方法。     

Highly efficient linearly polarised Raman generation in a germania-core optical fibre

The letter reports very efficient Raman generation and polarisation switching effects in a high-germania-content optical fibre, with a small 2?m2 core area. 10 dB Raman amplification has been observed in 5 m of fibre at a pump power of 2W. The Raman emission is only generated along the birefringence axes of the fibre.     

Loop-synchronous polarization scrambling technique for simulating polarization effects using recirculating fiber loops

A loop-synchronous polarization-scrambling technique has been proposed for the purpose of simulating polarization effects in straight-line systems using recirculating loops. This technique uses a fast polarization controller within a fiber loop. The polarization controller changes its transmission matrix after each round trip of the optical signal circulating through the loop; thus, the periodic polarization transform of the loop is avoided. Moreover, the polarization controller generates a series of random uncorrelated transmission matrixes. Therefore, the mean-square value of differential group delay (DGD) or polarization-dependent loss (PDL) increases linearly with the number of circulations. The matrix expression for a random polarization transform that scatters the state of polarization (SOP) uniformly on the Poincare sphere for any input SOP was also found. Experiments were performed for a 94-km fiber loop that contains a fixed DGD or PDL element. The histograms of polarisation mode dispersion (PMD) induced power penalties at 10/sup -9/ bit error rate (BER) were measured. There is a good agreement between experimental and theoretical results. Using loop-synchronous polarization scrambling, accurate reproduction of the Maxwellian distribution of DGD can be realized when the background PMD of transmission fiber is much smaller than the PMD intentionally introduced into the loop.     

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.<>     

Analog Full-Duplex Speech Scrambling Systems

This paper deals with the problems associated with full-duplex scrambled speech communications over analog two-wire telephone networks. The goal is not to describe particular scrambling systems or methods, but to analyze the situation in which the two users speak at the same time and each should hear the other. Current telephone scrambling devices preclude this feature. A general half-duplex scrambling model is described as a base to the discussion of pseudo- and true full-duplex communications. Finally, a novel true full-duplex scrambling architecture based on a paper by Cox and Tribolet [11] is presented.