Patent ID: 8041164

Claim:
A transition part ( 1 , 101 , 201 , 301 , 401 ) between two optical waveguides ( 2 , 3 ) with different index contrast, the transition part ( 1 , 101 , 201 , 301 , 401 ) comprising: a non-adiabatically and continuously up-tapered longitudinal section ( 8 ); an adiabatically down-tapered longitudinal section ( 10 ), arranged after the non-adiabatically up-tapered longitudinal section ( 8 ) as seen in a main propagation direction (L) of light, between said longitudinal sections a transition ( 7 ) between the two waveguides ( 2 , 3 ) is arranged along the main propagation direction (L) of the light; and a non-adiabatically down-tapered longitudinal section ( 9 ), arranged immediately after the non-adiabatically up-tapered longitudinal section ( 8 ) as seen in the main propagation direction (L) of the light, and the transition ( 7 ) between the two waveguides ( 2 , 3 ) is arranged between the non-adiabatically up-tapered longitudinal section ( 8 ) and the non-adiabatically down-tapered longitudinal section ( 9 ).