Abstract: An optical circuit device (1; 1′) has a substrate (6; 5′) with a surface (7; 7′) and a structural discontinuity (17; 17′) in the surface. The surface is provided with a light source (13: 13′) to emit light and a circuit element (15; 15′) whose performance is adversely affected by the incidence thereon of stray light emifted by the light source. To reduce optical cross-talk, the optical circuit device is provided with a barrier element (21; 21′) which is adapted to absorb light emitted by the light source. The barrier element is located in the structural discontinuity and is so positioned as to be able to absorb stray light embted by the light source The optical circuit device may be an optical transceiver having a laser diode and a photodiods.