Abstract: A system for detecting an optical output at a predetermined frequency, the system comprising: a plurality of optical guides for introducing an optical signal at said frequency into an input end of a dispersive optical component at each of a plurality of introduction sites corresponding to said optical guides; a detector located at the output end of the dispersive optical component and arranged to detect the optical power level of the optical signal introduced at each introduction site; means for establishing an optical power profile by interpolation of the optical power levels; and selection means for selecting the input optical guide at the introduction site at which the generated optical power level is spatially closest to the peak of the optical power profile.

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.

Abstract: The present invention relates to the electrical isolation of components within an integrated opto-electronic device where two or more active regions are optically coupled, for example by a waveguide. The device includes a distributed feed-back laser diode and an electro-absorption modulator fabricated on the same substrate. The laser diode and modulator are: separated by an electrical isolation region; linked optically across the isolation region by a waveguide; and capped by a ternary cap layer through which ohmic contacts are made to operate the components. The cap layer extends to the isolation region from which a grounding contact is made to ground the cap layer in the isolation region and so to electrically isolate the laser diode and modulator from each other.