Eric Tanguy

Modelling of the erbium–ytterbium laser

We have developed a modelisation of the Yb:Er glass laser system for pulsed regime. The model is first validated in CW regime with a good agreement with experimental values. The agreement in Q-switch mode is only qualitative. Nevertheless, tendences are outlined due to the particular dynamical behaviour of a codoped system. Especially, we pointed out the possibility of achieving Q-switch operation with pulse repetition frequency greater than the spontaneous de-excitation rate of the erbium upper level without output laser pulse characteristic degradation. On the other hand, gain-switch operation is not well suited for such codoped systems.

A 60 GHz Wireless Home Area Network With Radio Over Fiber Repeaters

Home area networks will have to deal with the future multigigabit wireless systems that are emerging or are under development . These millimeter-wave radio systems achieve data rates up to several Gb/s per channel, but over short distance. So, to expand the radio coverage, we propose to introduce a radio-over-fiber (RoF) infrastructure at home. This paper presents a complete study of a RoF system: the 60 GHz radio coverage is extended using a RoF link working at intermediate frequency with two hops in the air. An experimental setup of such an infrastructure has been realized and characterized. A low-cost solution, working at 850 nm, was chosen using multimode fiber and off-the-shelf millimeter-wave and photonic components. Finally, a real-time transmission between two commercial WirelessHD devices working at 3 Gb/s has been carried out.

Laser cleaning of tarnished silver and copper threads in museum textiles

Recent developments in laser techniques in the conservation field have allowed us to test the laser cleaning of tarnished silver and copper threads in textiles. The experimental samples were copper and silver plates that had been artificially sulphurised as well as silk bands dyed according to traditional procedures. The experiments were carried out with different Nd3+:YAG lasers emitting infrared, visible and ultraviolet radiation. The work has focused on optimising the cleaning process to control the side effects (whitening or yellowing of silver and reddening of copper) produced. Tests were also conducted on real artefacts, and the results are discussed.

Transmission Quality Measurement of Two Types of 60 GHz Millimeter-Wave Generation and Distribution Systems

In this paper, we demonstrate and compare experimentally two techniques achieving very high-data-rates (> 1 Gb/s) wireless transmission in the 60 GHz window using radio over fiber (RoF) for reach extension. The first RoF link is based on a 10 GHz vertical-cavity surface-emitting laser and uses a multimode fiber. The radio signal is transported on an intermediate frequency of 4.5 GHz and electrically upconverted to 60 GHz after the optical link. The second uses an optical frequency upconversion from 4.5 to 60 GHz by direct modulation of a mode-locked Fabry-PEacuterot laser whose self-pulsating frequency is 54.8 GHz before transmission over a single-mode fiber. For both techniques, two different types of modulation were tested. The first one was an on-off keying at 1.5 Gb/s and the second one was an orthogonal frequency-division multiplexing-QPSK signal compliant to the IEEE 802.15.3.c prestandard (3.03 Gb/s). Radio propagation performance is also reported.

Radio over Fiber tunnel for 60 GHz wireless home network

60GHz radio coverage is extended by using RoF at intermediate frequency with two hops in the air. MMF and low-cost photonics are used. Real-time transmission between two commercial Wireless-HD devices at 3Gbit/s is achieved.

Optical home network based on an N×N multimode fiber architecture and CWDM technology

With this optical home network solution associating an N×N multimode architecture and CWDM technology, various applications and network topologies are supported by a unique multiformat infrastructure. Issues related to the use of MMF are discussed.

High energy erbium laser end-pumped by a laser diode bar array coupled to a Nonimaging Optic Concentrator

A high energy Er3+, Yb3+:glass laser end pumped by a laser diode array emitting at 980 nm coupled to a Nonimaging Optic Concentrator (NOC) is demonstrated. Energy up to 100 mJ and a 16% slope efficiency are achieved in a plano-plano laser cavity. The energy transfer coefficient from Yb3+ to Er3+ is estimated by a new method.

Accelerated aging and life tests of optical fibers

The reliability of the network optical fibers is a critical issue for telecommunications. New investigations methods have been developed within a cooperative program supported by France Telecom. They include low coherence interferometry and optical near field microscopy in association with classical analysis tools such as Scanning Electron Microscopy and Shear Force Microscopy. One aim of the study is the localization and the characterization of the defects from which failure originates. The aging effect has been investigated in silica fibers immersed in desionized water at 65 °C and 85 °C for different times : from 3 to 12 months

Lasers Cleaning of Patrimonial Plasters

The use of the lasers Q-switched Nd:YAG to remove the dust of the stone monuments especially sculpture gradually replaces the more abrasive technique of sandblasting. This tendency made us consider the lasers as solution for the cleaning of ceramics and the plasters. Indeed in museums, these materials are often covered with dirty mark (dust, grease, etc.) which is difficult to remove without damaging the object. This paper deals with the impact of different types of lasers (Nd:YAG first and third harmonic) irradiation on plaster and with the effects on its morphology and its crystallography. Plaster is an interesting material because of its typical acicular crystals altered at low temperature. That is why synthesis samples were prepared, constrained in temperature then analysed by various processes (SEM, XRD, TGA. . . ). These results were compared with samples cleaned by laser. That enabled us to conclude that plasters cleaned by UV-laser (third harmonic of the Nd:YAG) underwent neither yellowing, nor morphological or crystallographic changes. It has to be opposed to the intense yellowing, and sometimes morphological destruction, which appears with an infrared wavelength (first harmonic of the Nd:YAG).

N × N coupler uniformity in a CWDM passive star home network based on multimode fiber: A time-effective calculation method

Optical fiber is the most appropriate medium able to meet future requirements in terms of capacity and heterogeneity in the home network. The advantages of a passive star architecture associated with wavelength multiplexing have already been reported. For lower-cost issues, multimode fiber would be preferred, but some problems were raised related to poor uniformity of the N × N multimode coupler when using the usual coarse wavelength division multiplexing sources. An original time-effective method is proposed, based on both simulation and calculation. Many results are provided, giving a better understanding of the behavior of the N × N coupler when different types of sources are used, also taking into account improvement techniques such as offset launching or mode scrambling.