I. Introduction
Data centers (DCs) are facing the challenge of delivering more capacity over longer distances. As line rates increase to 50 Gb/s and higher, DCs are being challenged with signal integrity issues due to the long electrical traces that require re-timing. One proposal to overcome these issues is to use optical transceivers with co-packaged optics in which fibers are used to transport data to and from the front panel. These small footprint transceivers, such as those that conform to the Quad Small Form-Factor (QSFP) and Consortium for On-Board Optics (COBO) “Class A” specifications, require the height of the optical fiber components to be less than about 3.8 mm. In order to conform to the small vertical form factor, the light needs to make a right angle turn over a very small radius – in the 2 to 2.5 mm range. While this light turn can be done with lenses and/or mirrors, the difficulty of aligning an array of these micro-optic components has motivated designs in which fiber array units are bonded to the SiP chip and incorporate a small radius ~90° bend in the same fibers that transmit the signal to the edge of the chip.