Biblio

A full-duplex self-recovery optical fibre transport system is proposed on the basis of a novel passive single-line bidirectional optical add/drop multiplexer (SBOADM). This system aims to achieve an access network with low complexity and network protection capability. Polarisation division multiplexing technique, optical double-frequency application and wavelength reuse method are also employed in the transport system to improve wavelength utilisation efficiency and achieve colourless optical network unit. When the network comprises a hybrid tree-ring topology, the downstream signals can be bidirectionally transmitted and the upstream signals can continuously be sent back to the central office in the reverse pathways due to the remarkable routing function of the SBOADM. Thus, no complicated optical multiplexer/de-multiplexer components or massive optical switches are required in the transport system. If a fibre link failure occurs in the ring topology, then the blocked network connections can be recovered by switching only a single optical switch preinstalled in the remote node. Simulation results show that the proposed architecture can recover the network function effectively and provide identical transmission performance to overcome the impact of a breakpoint in the network. The proposed transport system presents remarkable flexibility and convenience in expandability and breakpoint self-recovery.

Arabic handwritten documents present specific challenges due to the cursive nature of the writing and the presence of diacritical marks. Moreover, one of the largest labeled database of Arabic handwritten documents, the OpenHart-NIST database includes specific noise, namely guidelines, that has to be addressed. We propose several approaches to process these documents. First a guideline detection approach has been developed, based on K-means, that detects the documents that include guidelines. We then propose a series of preprocessing at text-line level to reduce the noise effects. For text-lines including guidelines, a guideline removal preprocessing is described and existing keystroke restoration approaches are assessed. In addition, we propose a preprocessing that combines noise removal and deskewing by removing line fragments from neighboring text lines, while searching for the principal orientation of the text-line. We provide recognition results, showing the significant improvement brought by the proposed processings.