US 5,850,283 AGranted

Determination of angular position of weak axial asymmetries of optical fibers and alignment of and splicing fibers

AssigneeTelefonaktiebolaget LM Ericsson

InventorWenxin Zheng

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Abstract

In determining the angular rotational position of axial asymmetries of bodies like optical PM-fibers such a body or fiber is illuminated during rotations thereof to different angular positions around its longitudinal axis. For different angular positions the difference is then determined between light, which has passed through the fiber end and in its position corresponds to the central part of the fiber, and light, which has passed through the fiber end and in its position corresponds to the region of the fiber located immediately outside the central part. These differences, considered as a function of the rotation angle, constitute a curve that is analyzed for finding the regions thereof having the steepest descent or increase, such as a valley region. Only these regions are then used for determining the position of the optical asymmetries. Thus the fiber can be rotated during only this interval determining the curve more accurately by using more densely spaced measurement points within the interval. Such a determination is particularly suited for PM-fibers having very small optical asymmetries such as fibers having an elliptical core.

Claims21

Dependent claims

A method of determining the angular position about a longitudinal axis of at least one axial optical asymmetry located in parallel to the longitudinal axis of a cylindrical body, the body being located in an arbitrary angular start position about its longitudinal axis, comprising the steps of:

illuminating the body by a light beam in a direction crossing the body, the light beam comprising light for which the body is transparent,
rotating the body through an angular interval having a first predetermined angular extension being at least half a full turn from the start angular position about the longitudinal axis,
determining during the rotation, for a predetermined first number of different angular positions, the difference between light intensity of light, which has passed through the body and in its position corresponds to the central portion of the body as seen in the longitudinal direction, and of light which has passed through the body and in its position corresponds to regions located most close to and outside the central portion of the body,
determining from the determined differences as a function of the rotation angle from the start angular position at least one rotation angle interval, where the function has its most rapid variation or where the function is strictly decreasing or increasing and has the highest absolute value of its derivative, and
evaluating the function values within the at least one rotation angle intervals for determining a value of the angular position of the least one optical asymmetry in relation to the start angular position of the body or a value of the angular position of the body in relation to some fixed reference angular position of the body.

2 more elements

A device for determining, for a cylindrical body which has a longitudinal axis and at least one axial optical asymmetry and which is located in an arbitrary angular start position about the longitudinal axis, of the angular position of the at least one axial optical asymmetry about the longitudinal axis comprising

means for illuminating the body with a light beam crossing the body,
means for rotating the body through an angular interval having a predetermined first extension being at least half a full turn from its angular start position about its longitudinal axis,
means for determining, during the rotation, for different angular positions the difference between the light intensity of light which has passed through the body and in its position corresponds to the central longitudinal portion of the body and of light which has passed through the body and in its position corresponds to the region outside an at the longitudinal central portion of the body,
means for determining from the determined differences as a function of the rotation angle from the start angular position at least one rotation angle interval, where the function has its most rapid variation or where the function is strictly decreasing or increasing and has the highest absolute value of its derivative, and
means for evaluating the function values within the at least one rotation angle interval for determining a value of the angular position of the least one optical asymmetry in relation to the start angular position of the body or a value of the angular position of the body in relation to some fixed reference angular position of the body.

2 more elements

Dependencies are inferred from the claim text.