Patent ID: 7027702

Claim:
An optical waveguide comprising: a lower clad layer formed on a substrate; a core layer formed on the lower clad layer; and an upper clad layer in which the core layer is buried; wherein at least the core layer and the upper clad layer are made of a material comprising a glass as a major component; wherein a coefficient of linear expansion of the core layer is denoted by α core , a difference between a softening temperature T core of the core layer and a practically used temperature T o by ΔT core , a coefficient of linear expansion of the upper clad layer by α clad , a difference between a softening temperature T clad of the upper clad layer and the practically used temperature T o by ΔT clad , and a coefficient of effective linear expansion of the substrate and of the lower clad layer by α subs , then, a relationship, Δ ⁢ ⁢ T core Δ ⁢ ⁢ T clad = 2 ⁢ α core - α subs - α clad α core - α subs is satisfied.