# US 5,349,431 A · Apparatus for measuring cross-sectional distribution of refractive index of optical waveguide

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- Number: US 5,349,431 A
- Document ID: US5349431A
- Status: Granted
- Kind: A
- Application number: 08/085,200
- Filed: 1993-06-30
- Granted: 1994-09-20
- Earliest claimed: 1993-06-30
- Assignees: Topcon Corporation
- Inventors: Nicolas Gisin; Patrick Stamp; Rogerio Passy; Nobuo Hori; Shigenori Nagano
- Web page: https://patentgrep.com/patent/US5349431A

## CPC

- G01N 21/412: {Index profiling of optical fibres}
- G01N: INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES (measuring or testing apparatus or processes other than immunoassay, involving enzymes or microorganisms C12M, C12Q)

## Abstract

An optical waveguide portion is provided on one surface of a substrate portion. A luminous flux for measurement is caused to be incident on one end face of the optical waveguide substrate, and only leaking light having passed through the substrate portion is received. The cross-sectional distribution of the refractive index of the optical waveguide portion is measured from changes in the received quantity of light.

## Claims

### Claim 1

An apparatus for measuring the cross-sectional distribution of the refractive index of an optical waveguide, comprising a projector system for causing a luminous flux for measurement to be incident on one end of an optical waveguide portion provided on one surface of a substrate portion and a light-receiving unit for receiving leaking light of said luminous flux for measurement from said optical waveguide portion, characterized in that said light-receiving unit is arranged at the other end of said optical waveguide portion such as to receive only leaking light having passed through said substrate portion, wherein the cross-sectional distribution of the refractive index of said optical waveguide portion is measured from changes in the amount of light incident on said light-receiving unit.

### Claim 2 (depends on 1)

The apparatus for measuring the cross-sectional distribution of the refractive index of an optical waveguide according to claim 1, wherein the light-receiving unit and the substrate portion are in close contact with each other.

### Claim 3 (depends on 1)

The apparatus for measuring the cross-sectional distribution of the refractive index of an optical waveguide according to claim 1, wherein a light-receiving unit is disposed on the outer side of the maximum exit angle light of the exit luminous flux from the optical waveguide portion.

### Claim 4 (depends on 1)

The apparatus for measuring the cross-sectional distribution of the refractive index of an optical waveguide according to claim 1, wherein an unsensitising portion is provided at a light-receiving unit to prevent said light-receiving unit from receiving the luminous flux from the optical waveguide.

### Claim 5 (depends on 1)

The apparatus for measuring the cross-sectional distribution of the refractive index of an optical waveguide according to claim 1, wherein the surface of the optical waveguide substrate is polished, at which the optical waveguide is not provided.

### Claim 6 (depends on 1)

The apparatus for measuring the cross-sectional distribution of the refractive index of an optical waveguide according to claim 1, wherein the surface of the optical waveguide substrate is a diffusing surface, at which the optical waveguide is not provided.