Variable optical fiber grating and dispersion compensator

A dispersion compensator which compensates chromatic dispersion of an optical transmission, said dispersion compensator comprising a variable optical fiber grating, wherein said variable optical fiber grating comprises:

• an optical fiber grating;
• and
• a fixing member,
• wherein said optical fiber grating is fixed in said fixing member,
• said fixing member comprising at least a first and a second materials, the first material having a higher coefficients of linear expansion than the second material, the second material with the lower coefficient of linear expansion surrounding the first material with the higher coefficient of linear expansion, and
• wherein the optical fiber grating is constituted such that an expansion coefficient and contraction coefficient of said optical fiber grating changes along the longitudinal direction of said optical fiber grating following the expansion and contraction of the first material with the higher coefficient of linear expansion, whereby an amount of chromatic dispersion is varied by temperature modulation by adjusting a fixing position of said optical fiber grating.

A variable optical fiber grating comprising:

• an optical fiber;
• a first material;
• and
• a second material,
• wherein at least a portion of said optical fiber is fixed within the first and second material, said portion constituting an optical fiber grating,
• the first material has a higher coefficients of linear expansion than the second material, and
• the second material is surrounding the first material.