Cross-talk reduction in a bidirectional optoelectronic device

A bidirectional optoelectronic device comprising:

• (a) a waveguide substrate;
• (b) a set of one or more optical waveguide layers on the substrate;
• (c) one or more optical waveguides formed in one or more of the optical waveguide layers, each of the optical waveguides being arranged to substantially confine in two transverse dimensions a corresponding guided optical mode;
• (d) one or more electrical traces on the substrate;
• (e) a first optoelectronic component comprising a photodetector arranged (i) to receive via at least one of the one or more optical waveguides an input optical signal modulated to encode first transmitted information and (ii) to generate in response to the input optical signal and to transmit via at least one of the one or more electrical traces an output electrical signal modulated to encode the first transmitted information;
• (f) a second optoelectronic component comprising a light source arranged (i) to receive via at least one of the one or more electrical traces an input electrical signal modulated to encode second transmitted information, (ii) to generate in response to the input electrical signal an output optical signal modulated to encode the second transmitted information, and (iii) to launch a first fraction of the optical signal to propagate along one of the optical waveguides in the corresponding guided optical mode;
• (g) one or more light collectors formed in the optical waveguide layers, each light collector comprising one or more lateral surfaces of the optical waveguide layers and a substantially opaque coating on the lateral surfaces;
• (h) one or more light traps formed in the optical waveguide layers, each light trap comprising one or more lateral surfaces of the optical waveguide layers and a substantially opaque coating on the lateral surfaces,
• (i) a protective encapsulant arranged to encapsulate the photodetector, the light source, at least portions of the one or more optical waveguides, at least portions of the one or more light collectors, at least portions of the one or more light traps, and at least portions of the one or more electrical traces,
• wherein:
• (j) the lateral surfaces of each light trap are arranged to define a corresponding spiral region of the optical waveguide layers, which region includes an open mouth and closed end of the light trap;
• (k) the lateral surfaces of each light collector are arranged to redirect a corresponding portion of a second fraction of the optical signal to propagate into the open mouth of one of the light traps, which second fraction of the optical signal propagates from the light source in one or more of the optical waveguide layers without confinement by any of the optical waveguides in the corresponding guided optical modes;
• (l) the encapsulant includes hollow dielectric microspheres dispersed within its volume so as to reduce a cross-talk penalty arising from unwanted electrical signals present in the encapsulant to a level below that exhibited by the bidirectional device without the microspheres in the encapsulant;
• and
• (m) the encapsulant further includes an optical absorber dispersed within its volume so as to reduce a cross-talk penalty arising from unwanted optical signals present in the encapsulant to a level below that exhibited by the optoelectronic device without the optical absorber in the encapsulant.