US 5,513,913 AGranted

Active multipoint fiber laser sensor

AssigneeUnited Technologies Corporation

InventorsGary A. Ball, Gerald Meltz, Leon A. Newman

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Abstract

A remote active multipoint fiber laser sensor includes a plurality of fiber lasers 12,14,16, each having a pair of Bragg gratings 18,20, embedded in a fiber 10 and excited by a common pump light 30. The lasers 12,14,16 lase at different longitudinal modes (lasing wavelengths) and emit light 32,34,36, at their respective wavelengths .lambda.1,.lambda.2,.lambda.n. The lasing wavelength of each laser shifts due to perturbations, such as strain or temperature, applied thereto. The output light 32,34,36 is fed to a spectrum analyzer 50 where the wavelength shift is analyzed. A signal processor 54 reads the wavelength shift and provides a signal on lines 56 indicative of the perturbation at each of the lasers/sensors 12-16. Alternatively, a single laser may be used as a single sensor. Alternatively, birefringent fiber may be used as the fiber cavities 21 and the two polarizations are beat together to form a lower difference or "beat" frequency, thereby allowing lower frequency detection devices to be used.

Claims13

Dependent claims

A remote active multipoint laser sensor, comprising:

an optical waveguide for receiving and propagating a pump light of a predetermined wavelength launched into said optical waveguide;
a plurality of lasers, disposed successively along said waveguide, each being pumped by said pump light, at least a portion of at least one of said lasers sensing a perturbation in said optical waveguide, each having a lasing wavelength different from the lasing wavelength of the other lasers, each emitting an output light at said lasing wavelength, and said lasing wavelength being related to the magnitude of said perturbation;
each of said lasers having a pair of reflective gratings and having a gain medium therebetween, at least one of said gratings being reflective over a narrow wavelength band which includes said lasing wavelength, and each of said gratings having a reflective wavelength spectrum;
and
said lasing wavelengths of said lasers being spaced such that there is minimal overlap between said reflective wavelength spectrums of said gratings from different ones of said lasers over the range of the magnitude of said perturbation to be sensed.

2 more elements

Dependencies are inferred from the claim text.

Facts

Application: 08/069,231Filed 28 May 1993 · continuation in part
Priority: 29 Jan 1993
Granted: 7 May 1996
Term ends: Not estimatedThe source records don’t support an estimate.

Classification6 codes

G01D 5/35383
Influencing the transmission properties of an optical fibre: using multiple sensor devices using multiplexing techniques
G01J 3/1895
Using diffraction elements, e.g. grating: using fiber Bragg gratings or gratings integrated in a waveguide
H01S 3/0675
Fibre lasers: resonators including a grating structure, e.g. distributed Bragg reflectors [DBR] or distributed feedback [DFB] fibre lasers
G01D
Measuring not specially adapted for a specific variable