Embedded faraday rotators and components for increasing bandwidth and/or reducing fiber count in photonics multi chip packages

A photonics device, comprising:

• a package substrate, the package substrate comprising a plurality of conductive routing layers;
• a photonics die over a first surface of the package substrate;
• a multiplexer over a second surface of the package substrate;
• a first optical path from the photonics die to the multiplexer for propagating a first optical signal;
• and
• a second optical path from the photonics die to the multiplexer for propagating a second optical signal, wherein a magnetic shell and an optically clear plug filling the magnetic shell is provided along the second optical path to convert the second optical signal from a first mode to a second mode before reaching the multiplexer, wherein the magnetic shell and the optically clear plug are within an opening in the package substrate, the optically clear plug extending from a top of the package substrate to the multiplexer.