Herve Lefevre

Wavelength stabilization of an erbium-doped fiber source with a fiber Bragg grating for high-accuracy FOG

We present a method of stabilization of the mean wavelength of a superluminescent erbium-doped-fiber source which is obtained with a fiber Bragg grating acting as a broad spectral filter. This allows one to get 10 ppm stability over temperature. Excess intensity noise is reduced with a biasing phase modulation of the FOG about +/- (pi) radian instead of the usual +/- (pi) /2 radian.

Latest advances in fiber optic gyroscope technology at Photonetics

We describe our activity on interferometric fiber-optic gyroscope (I-FOG) technology: recent results on our improved large-operating-range prototypes (FOG 50); development on three- axis clusters using a single source; work on high-performance I-FOGs (FOG 125) using an Erbium doped fiber source. We also present our approach to wavelength control.

Metricor 2000: a multiparameter fiber optic sensor instrument

The METRICOR 2000 instrument has been developed as a solution to numerous needs for fiber optic sensors in metrology and in process control. It is able to measure over 20 different physical parameters through three different operating principles, corresponding to three different conditioners. A first intensity conditioner is designed to deal with signal generated by probes with a limited dynamic range. It is particularly suited for on/off sensors such as level detection and void fraction probes. A dual wavelength conditioner handles signals generated by probes requiring referenced operation. It can be used with opacimetry and chemical concentration probes as well as fail-safe dual wavelength on/off type sensors. A third conditioner deals with the complex signal generated by interferometric sensors. Those sensors, operating under a white light illumination, return a spectrally encoded information which is not affected by on-line attenuation. This third conditioner can be used with micro-machined interferometric temperature, pressure or index of refraction sensors. It offers the highest performance in resolution and accuracy. The standard mainframe unit includes a display for 4 simultaneous measurements. Each probe is equipped with an electronic personality key which includes the calibration.

FOG multiplexing by time-shifted phase modulation

We present a new method to multiplex multi-axis FOGs. A 2 X N coupler is used to share a light source between N Sagnac interferometers. They are all modulated with usual square wave phase modulations, but these modulations are shifted in time by (tau) /N where (tau) is the mean transit time into a coil. The total optical signal coming back from the interferometer is detected with a single photodiode and then demultiplexed. This multiplexing technique has the important advantage to yield a constant bias power even when the powers returning from the various interferometers are not balanced. The closed-loop configuration allows no crosstalk between the N axes far from the cut-off frequency.

Gyrofibre pour le spatial

This paper, “Gyrofibre pour le spatial, was presented as part of International Conference on Space Optics—ICSO 1997, held in Toulouse, France.

Développement d'un capteur optique de pression pour la mesure in-situ des moteurs cryogéniques

This paper, “Développement dun capteur optique de pression pour la mesure in-situ des moteurs cryogéniques, was presented as part of International Conference on Space Optics—ICSO 1997, held in Toulouse, France.

Diode laser à cavité externe auto-alignée et contlnûment accordable en longueur d'onde

This paper, “Diode laser à cavité externe auto-alignée et contlnûment accordable en longueur donde, was presented as part of International Conference on Space Optics—ICSO 1997, held in Toulouse, France.

High power ASE-free tunable laser using a Sagnac ring interferometer within the external cavity

The use of a Sagnac ring interferometer within the external cavity of a tunable laser diode is described. This optical scheme provides an ASE-free output, without any reduction of the output power.

Development of a fiber optic sensor network for naval applications

This paper describes the development of a complete fiber optic sensor network demonstrator, installed on a naval warfare simulator system. It incorporates a 64 on/off multiplexed optical sensor network together with single point analog optical sensors. A complete description of the system is given showing the different sensors that have been developed and their specific applications. We also discuss the experimental results and the potential advantages of this technology for naval systems.

Simple optimization of the interferometric measurement of polarization-mode dispersion

Summary form only given. Several interferometric schemes that perform the cross-correlation of orthogonal polarization states and avoid the central autocorrelation peak have been proposed. We show here that this can be done more easily with the sole insertion of a /spl Lambda//4 plate into one arm of the interferometer. By removing the output polarizer: the output light is depolarized but keeps the same whole spectrum as the one of the input polarized light.