High-sensitivity two-stage erbium-doped fiber preamplifier at 10 Gb/s

We have demonstrated an optical preamplifier with a record sensitivity of -38.8 dBm (102 photons/bit) at 10Gbit/s. When employed in a practical link without an input isolator the sensitivity is only slightly degraded to -37.6dBm (135 photons/bit) by input coupling losses and feedback due to Rayleigh backscattering in the transmission fibre

The teaching of other faiths in a traditionally oriented British Muslim School at Key Stage 3

This is a study of the teaching of other faiths at a traditionally oriented Muslim independent school in Britain. Traditional Muslim schools have gained a high profile for two reasons: Firstly they are founded upon the most traditional and orthodox of Islamic teachings which some fear may promote extremism and separatism. Secondly they provide the training for the next generation of religious leaders so the understanding and attitudes that are inculcated in their students can be expected to influence many in the Muslim community. The background to the study uncovered medieval scholarship that is rich in examples of the objective study of other faiths but also highlighted a contraction of the traditional syllabuses in the post-colonial period that has left traditional scholarship narrow and devoid of critical enquiry. The case study used semi-structured interviews with the staff and management to reveal the current curriculum and examine the attitudes of the staff and management towards the teaching of other faiths. The findings were that while the school’s ethos is very positive, the school is currently not engaged in any explicit teaching of other faiths. The root cause of this was found to be the failure of the school to establish any policies relating to either curriculum or pedagogy for the teaching of RE. This failing was then compounded by the appointment of an unqualified and inexperienced teacher for RE who did not share the positive vision of the management. The study also highlighted the lack of any established pedagogy for religious education rooted in orthodox Islam

Mode-multiplexed transmission over conventional graded-index multimode fibers

We present experimental results for combined mode-multiplexed and wavelength multiplexed transmission over conventional graded-index multimode fibers. We use mode-selective photonic lanterns as mode couplers to precisely excite a subset of the modes of the multimode fiber and additionally to compensate for the differential group delay between the excited modes. Spatial mode filters are added to suppress undesired higher order modes. We transmit 30-Gbaud QPSK signals over 60 WDM channels, 3 spatial modes, and 2 polarizations, reaching a distance of 310 km based on a 44.3 km long span. We also report about transmission experiments over 6 spatial modes for a 17-km single-span experiment. The results indicate that multimode fibers support scalable mode-division multiplexing approaches, where modes can be added over time if desired. Also the results indicate that mode-multiplexed transmission distance over 300 km are possible in conventional multimode fibers

Introduction

After a brief discussion of the evolution of optical networks in the last two decades, advanced modulation and coherent detection are pointed out as emerging key technologies for fulfilling the expected bandwidth demands of future optical fiber networks. Subsequently, an overview of current developments and today's state of research in the fields of advanced modulation and coherent detection is given. Finally, the scope of this book is localized and the chapter's contents are shortly outlined