# US 5,351,324 A · Fiber optic security seal including plural Bragg gratings

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- Number: US 5,351,324 A
- Document ID: US5351324A
- Status: Granted
- Kind: A
- Application number: 08/120,113
- Filed: 1993-09-10
- Granted: 1994-09-27
- Earliest claimed: 1993-09-10
- Assignees: The Regents of the University of California Office of Technology Transfer
- Inventors: Peter R. Forman
- Web page: https://patentgrep.com/patent/US5351324A

## CPC

- G09F 3/0376: {using a special technique to detect tampering, e.g. by ultrasonic or optical means}
- G09F: DISPLAYING; ADVERTISING; SIGNS; LABELS OR NAME-PLATES; SEALS

## Abstract

An optical security system enables the integrity of a container seal to be remotely interrogated. A plurality of Bragg gratings is written holographically into the core of at least one optical fiber placed about the container seal, where each Bragg grating has a predetermined location and a known frequency for reflecting incident light. A time domain reflectometer is provided with a variable frequency light output that corresponds to the reflecting frequencies of the Bragg gratings to output a signal that is functionally related to the location and reflecting frequency of each of the Bragg gratings.

## Claims

### Claim 1

A fiber optic security seal system, comprising:
an optical fiber having a plurality of reflective Bragg gratings induced in the fiber, where each grating has a unique location and wavelength for reflecting incident light;
a light source means for providing input light to said fiber at all of said wavelengths for reflecting light from said gratings;
a time domain reflectometer for receiving reflected light from said gratings and outputting a signal functionally related to said unique location and wavelength for reflecting incident light for each said grating; and
a coating over an end of said optical fiber receiving said incident light said coating having a crystal pattern that produces a unique holographic image to verify an identity of said optical fiber.

### Claim 2 (depends on 1)

A fiber optic security seal system according to claim 1, wherein said optical fiber has a core doped with germanium.