As an example:

Nubius insertion loss from the fiber into their waveguides is about 1dB. The same connection with POET is said to be .25 dB.  And since POET and only POET integrates both MUX and DE-MUX monolithically there are no couplings and no insertion loss across these device transitions. And no isolators which also creates losses in the competition.

 Waveguides: Our waveguides are designed to both be CMOS compatible and provide low loss characteristics. The material loss through the waveguides characterized by prism spectroscopy is <0.3dB/cm and is about one order of magnitude better than typically observed in small core silicon waveguides used in most other silicon photonics technologies. Moreover, our waveguides are largely athermal (dn/dT=12pm/°C) and are non-birefringent. A proprietary Spot Size Converter has been designed for chip facet fiber coupling achieving facet coupling losses of 0.25dB