Leland Stanford Junior University

Ifos, Inc.

Dario G Falquier

Michel J F Digonnet

H John Shaw

Jefferson L Wagener

Behzad M Moslehi

Michel J Digonnet

Craig W Hodgson

Vahid Sotoudeh

Levy Oblea

Brian Kutner

A fiber optic sensor comprises two independent fibers having Bragg gratings which are coupled to commutating broadband optical sources through splitters and wavelength discriminators. The ratio of detected optical energy in each of two detectors examining the wave intensity returned to a wavelength discriminator coupled with the characteristic of the wavelength discriminator determines the wavelength returned by the grating. In another embodiment, tunable filters are utilized to detect minimum returned wave energy to extract a sensor wavelength Reference to the original grating wavelength indicates the application of either temperature or strain to the grating. In another embodiment, a plurality of Bragg grating sensor elements is coupled to sources and controllers wherein a dimensional change in a fiber having a Bragg grating is detected using a measurement system comprising broad-band sources, optical power splitters, a high-sensitivity wavelength discriminator, optical detectors, and a controller.

Multiplexable fiber-optic strain sensor system with temperature compensation capability

The instability of the mean wavelength of a superfluorescent fiber source (SFS) is reduced by randomizing the polarization of light from a pump source or by using polarization maintaining components. In one embodiment, the polarization of a pump source is made more random, leading to greater stability of the mean wavelength of the SFS, with an output mean wavelength that is stable to better than 3 ppm for full rotation of the pump polarization state. In another embodiment, the polarization of optical radiation throughout the device is kept substantially constant by using polarization maintaining fiber and components, thereby leading to enhanced mean wavelength stability of the SFS.

Polarization and wavelength stable superflourescent sources

Polarization and wavelength stable superfluorescent sources

The wavelength stability of superfluorescent sources is controlled with optical arrangements in which the polarization-dependent gain (PDG) induced by the polarized pump light is reduced. In one apparatus and method, a Faraday rotator mirror is used at the end of the waveguide in the superfluorescent source. In another apparatus and method, the birefringence of the waveguide is exploited in conjunction with a Faraday rotator mirror to further average out the effect of PDG on the mean wavelength difference between the spectral outputs of orthogonal polarization components.

Polarization and wavelength stable superfluorescent sources using Faraday rotator mirrors

Fiber-amplified spontaneous emission sources incorporating spectral filters show an improvement in mean wavelength stability versus a number of operating factors, including pump wavelength, pump power, feedback, and temperature. By adjusting the spectral characteristics of the filter, the position of the filter along the length of the fiber, and the length of the rare-earth doped fiber, a stable ASE source is designed so as to provide stable operating points for the mean wavelength versus desired operating parameters. In many cases the sources show an improvement in mean wavelength stability by an order of magnitude or more over present sources.

Stable fiber ASE sources incorporating spectral filtering

A superfluorescent fiber source outputs highly polarized light without a substantial decrease in output power efficiency. According to one embodiment, a polarizer is spliced within the superfluorescent fiber at a selected location along the length of the fiber (e.g., near the middle of the fiber). According to another embodiment, the entire length of the superfluorescent fiber is polarizing to thereby assure that one of the polarizations of light is substantially extinguished while the other polarization of light is nearly double the power which that polarization would have if the polarizer were not present within the superfluorescent fiber. In this manner, superfluorescent sources can be adapted especially for use in fiber optic gyroscopes, or the like, which require highly polarized light, without a substantial reduction in efficiency.

Growing community of inventors

Palo Alto, CA, United States of America

Dario G Falquier