Until recently, fiber Bragg gratings have been found to exhibit three different growth mechanisms, type I, type II-arising from physical damage-and type IIA. Recently, it has been reported a new regime termed type IA. In this contribution we will report the observation of an abnormal growth mechanism of gratings written in high-Germanium-doped fibers, different from the referred types. First, we will identify possible causes for the observed evolution of the induced perturbation's characteristics (mean value and amplitude) as a function of the accumulated UV fluency. Then, we will analyze the thermal behavior (stability and sensitivity) of gratings formed through the referred abnormal mechanism and compare it with the obtained for the other well-known types (type I, IA and IIA), discussing the results and possible applications in sensing and optical communications areas.
In this contribution we compare the thermal stability of type I and type IIa gratings written in germanosilicate fibers. We study and compare their central wavelengths drifts and variations of the maximum reflectivity with temperature. Also, two other important factors, the bandwidth and group delay characteristics are characterized, compared, and the differences justified, based on the gratings physical structure.
In this contribution the routing capabilities of time/wavelength codes in Optical Code Division Multiple access are observed by means of the study of two devices for achieving the wavelength part code conversion. Multi-wavelength conversion will be achieved by using a Semiconductor Optical Amplifier and a Reflective Semiconductor Optical Amplifier. The conversion results for the two devices will be characterized and compared in terms of applicability to the conversion in hands and to the referred application.
This paper summarizes the research activities of the optical communications group at University of Aveiro and Institute of Telecommunications-Aveiro pole. Several activities like clock recovery systems, both electrical and all optical, electrical equalizers for very high bit rate DST systems, post-detection filters for multigigabit optical receivers, soliton systems, simulation work on WDM, DST, EDFA and short pulse generation for high bit rate systems are presented.
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