The first and second polymeric materials differ from each other in refractive index by at least about 0.03.

The coating layer that is in contact with the transparent negative electrode has a refractive index difference of 0.1-0.7 (inclusive) from that of the transparent negative electrode (8).

The second functional layer that is in contact with the transparent negative electrode (8) has a refractive index difference of 0.1-0.7 (inclusive) from that of the transparent negative electrode (8).

The first and second polymeric materials differ from each other in refractive index by at least about 0.03.

The polymer optical fibers can have a variety of index refraction profiles, such as step index or GRIN (graded-index) profiles.

The index characters are arranged along the arc borderline, and the index indicator is positioned in the index operation region and used for indicating the selected index characters.

abrupt change in the speed of light

The fibers may be of the step-index or graded-index type.

The first refractive index contrast is smaller than the second refractive index contrast.

The second reference index value is different than the first reference index value.

A graded index fiber formed of a plurality of fused graded index fibers is provided.

The coating layer that is in contact with the transparent negative electrode has a refractive index difference of 0.1-0.7 (inclusive) from that of the transparent negative electrode (8).

A first of the layers is of uniform refractive index n! surrounding a second of the layers of uniform refractive index n2.

The subject invention is applicable to step index optical fiber and to graded index optical fiber.

The second functional layer that is in contact with the transparent negative electrode (8) has a refractive index difference of 0.1-0.7 (inclusive) from that of the transparent negative electrode (8).