Solvatochromic and halochromic behaviour in the u.v.‐vis absorption spectra of some substituted 4‐arylidene‐2‐aryloxazol‐5‐ones (1–5) are studied. Positive and negative solvatochromism, depending on the substituent present, are observed in different hydrogen bonding donoracceptor (HBD‐A) and hydrogen bonding acceptor (HBA) solvents. However, in non hydrogen bonding (NHB) solvents all compounds show a positive solvatochromism. A considerable intramolecular charge transfer interaction, between the donor and acceptor parts in the oxazolones studied, is observed. Small fluorescence quantum yields are observed for the oxazolones. In triethanolamine‐acetone mixtures, the visible absorption spectra of the hydroxy substituted oxazolone shows an additional long‐wavelength band suggesting the existance of prototropic equilibria. The prototropic equilibrium constants at different temperatures are determined.

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All-Optical Clock and Data Recovery (OCDR) is considered the most promising technique to increase the optical networks distance and the data rate by synchronizing and regenerating the data along the fiber cable, consequently achieving small Bit Error Rate (BER) at the receiver end. In this paper, we design and implement the OCDR using two different techniques, Self-Pulsating (SP) using Distributed Bragg Reflector laser (DBRL) and Filtering based using Fiber Brag Grating (FBG). A comparative study and measurement of the network performance for the two methods have been presented. The experimental results show clearly the increase either transmission distance or the bitrate.

Clock and data recovery (CDR) is an essential part in high-speed telecommunication systems. The CDR is used to extract the clock and re-time the received data, which allows a synchronous operation to recover the transmitted signal. In optical access networks, electrical CDR or optical CDR implementations can be used. However, there are no clear guidelines or recommendations on which CDR implementation should be adopted for better performance. These missing clear recommendations are because the electrical CDR requires electronics design expertise whereas the optical CDR requires optical design expertise. Consequently, in this paper, an all-digital CDR, designed and implemented on the field-programmable gate array platform, and an optical CDR, developed by using fiber Bragg grating technology on the OptiSystem platform, are presented. Furthermore, the integration of these 2 CDR implementations with the optical access network is implemented, and their performance is evaluated for various transmission rates and communication distances. Finally, a comparative study in terms of the bit error rate between the all-digital CDR and the optical CDR is presented. KEYWORDSclock and data recovery, fiber Bragg grating, field-programmable gate array, optical access network 1 Int. J. Commun. Syst. 2016; 29: 2555-2564 wileyonlinelibrary.com/journal/dac

ChemInform Abstract (solvatochromic and halochromic behavior in the UV/VIS absorption spectra).