Optical device for reducing temperature related shift

1. An optical device having a plurality of optical waveguides and comparing at least one waveguide, which is defined by a core region having first and second sections that are series connected and are capable of transmitting light energy, the core region being surrounded by a cladding that essentially confines the light energy within the core region, the first section of the core region comprising a first length of material whose refractive index increases as temperature increases,

wherein the at least one waveguide is temperature-compensating and the second section of the core region comprises a second length of material whose refractive index has a sufficient enough difference of the rate of the variation of the index with the temperature,

wherein the second section has a plurality of grooves, filled with the material whose refractive index has a sufficient enough difference of the rate of the variation of the index with the temperature, that are designed in a way the effective width of the second section changes between adjacent wave-guides and where each groove of the second section has the shape of a triangle over its whole length, and the grooves of the second section have different pseudo randomize widths uniform along the lengths of the grooves.

2. The optical device of claim 1 , wherein the second material has a temperature coefficient that decreases when the temperature increases.

3. The optical device of claim 1 , wherein second material has a temperature coefficient which increases but with a rate of variation different from the temperature coefficient of the first material.

4. The optical device of claim 1 , wherein the first section of the core region is made of silica.

5. An optical device having a plurality of optical waveguides and comparing at least one waveguide, which is defined by a core region having first and second sections that are series connected and are capable of transmitting light energy, the core region being surrounded by a cladding that essentially confines the light energy within the core region, the first section of the core region comprising a first length of material whose refractive index increases as temperature increases,

wherein the at least one waveguide is temperature compensating and the second section of the core region comprises a second length of material whose refractive index has a sufficient enough difference of the rate of the variation of the index with the temperature,

wherein the second section has a plurality of grooves, filled with the material whose refractive index has a sufficient enough difference of the rate of the variation of the index with the temperature, that are designed in a way the effective width of the second section changes between adjacent wave-guides and where each groove of the second section has the shape of a triangle over its whole length, and the grooves of the second section have non uniform widths along the lengths of the grooves but the same lengths.

6. The optical device of claim 5 , wherein the second material has a temperature coefficient that decreases when the temperature increases.

7. The optical device of claim 5 , wherein second material has a temperature coefficient which increases but with a rate of variation different from the temperature coefficient of the first material.

8. The optical device of claim 5 , wherein the first section of the core region is made of silica.

9. An optical device having a plurality of optical waveguides and comparing at least one waveguide, which is defined by a core region having first and second sections that are series connected and are capable of transmitting light energy, the core region being surrounded by a cladding that essentially confines the light energy within the core region the first section of the core region comprising a first length of material whose refractive index increases as temperature increases,

wherein the at least one waveguide is temperature-compensating and the second section of the core region comprises a second length of material whose refractive index has a sufficient enough difference of the rate of the variation of the index with the temperature,

wherein the second section has a plurality of grooves, filled with the material whose refractive index has a sufficient enough difference of the rate of the variation of the index with the temperature, that are designed in a way the effective width of the second section changes between adjacent wave-guides and where each groove of the second section has the shape of a triangle over its whole length, each groove of the second section has the shape of a single trapezoid, and the trapezoids are created by the triangle with one side length a and by an attached rectangular shape with one side length b.

10. The optical device of claim 9 , wherein the side length of each trapezoid follows the rule a=b.

11. The optical device of claim 9 , wherein the side lengths of each trapezoid follows the rule b=2a.

12. The optical device of claim 9 , wherein the second material has a temperature coefficient that decreases when the temperature increases.

13. The optical device of claim 9 , wherein second material has a temperature coefficient which increases but with a rate of variation different from the temperature coefficient of the first material.

14. The optical device of claim 9 , wherein the first section of the core region is made of silica.