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International audience; Laser spectra are strongly modified by the optical feedback which is provided by external cavities; here we give a preliminary experimental result describing the optical spectrum of a fibre laser having two identical end cavities, which appear between the external mirrors and fibre ends. One observes a channelled spectrum including mode clusters separated by empty regions. We use the optical Airy function defined in the pure frequency domain to study these spectra. An optical Vernier effect allows the description of this structure. The linewidth of each mode is calculated as a function of the gain, by using the same Airy function.

The Free Space Optic (FSO) communication is a daily reality used by an increasing number of companies. For indoor environment, optical wireless communication becomes a good alternative with respect to radio proposals. For both technologies, the architecture is similar: emission/reception base station (Gateway or Bridge) are installed to cover zones, which are defined to ensure a quality of service. The customers may be connected to the Wireless Local Area Network (WLAN) with an adapter or module that emits and receives on this network. But due to its specific characteristics, wireless optical technology could present important advantages such as: Transmitted data security, medical immunity, high data rate, etc... Nevertheless, the optical system may have a limit on the network management aspect and link budget. The scope of this paper is to present a proposal at crossroads between optical fibre telecom system and data processing. In this document, we will present a prototype developed in Brittany during a regional collaborative project (Techim@ges). In order to answer to the management aspect and the link budget, this prototype uses an optical multiplexing technique in 1550 nm band: the Wavelength Division Multiple Access (WDMA). Moreover it also proposes a new class 1 high power emission solution. This full duplex system transmits these various wavelengths in free space, by using optical Multiplexer/Demultiplexer and optical modules. Each module has a defined and personal wavelength associated to the terminal identification (addresses MAC or IP). This approach permits a data rate at a minimum of a ten's Mbit/s per customer and potentially hundred Mbps for a line of sight system. The application field for the achieved and proposed prototype is potentially investigated from WLAN to WPAN.

topic « Lasers and laser applications »; International audience; We present the experiment that allows multiwavelength operation and tunability of a neodymium-doped fiber laser with an intracavity polarizer. Then, we present the experimental method to extract the Jones matrix of the fiber as a function of the wavelength. Hence, using the round-trip operator method, we compare both experimental and theoretical wavelength selection and find a excellent agreement.

conference 5452 « Semiconductor Lasers and Laser Dynamics », session 4 « Short Pulses and Mode-Locking » [5452-18]; International audience; A semiconductor laser coupled to a gallium-made non linear mirror may exhibit pulse regime. In order to better understand this coupled cavity, stationary solutions and dynamics are described following the standard Lang and Kobayashi equations for a semiconductor laser submitted to nonlinear optical feedback. It is shown that the nonlinearity distorts the ellipse on which lied the stationary solutions, with a "higher" part corresponding to lower reflectivity and a "lower" part to higher reflectivity. Bifurcation diagrams and nonlinear analysis are presented while the conditions for pulsed operation are discussed.

International audience; We report that a bubble with a radius of a few micrometers may be created at a precise location on a metal-coated optical fiber tip immersed in liquid nitrogen by microsecond optical pulses with peak powers of less than 20 mW. Dynamic optical measurements reveal that after termination of the optical pulse the bubble exhibits stable oscillations for several tens of microseconds, at frequencies up to several megahertz, as it slowly collapses.

The purpose of this paper is to calculate the radiation from bent single-code optical fibers along arbitrarily oriented curved shape, which we call 'single-mode optical fiber antennas' (SMOFA). A generalized voluie current cethod (VCM) is used in order to determine the radiated power of a N-iultiturn optical fiber antenna in the fore of circular helix. The resulting loss formula reduces in the case of N1 to the well known atennuation forsula of the the bent single-code fibers.