Spot Size Converting (SSC) Fiber Arrays

PHIX has been using fiber arrays with an edge assembly scheme to couple directly to Silicon Nitride chips with integrated spot size converter in these chips.

For materials like Indium Phosphide (InP), Lithium Niobate (LiNbO3), and Silicon Photonics (SiP) this was not feasible due to the absence of integrated spot size converter building blocks on the chip.

In order to couple fibers to such chips one would use high NA fibers, or specially tapered fibers. However, scalability to multichannel configurations is a challenge since core concentricity and cladding diameter tolerance variation of the fibers immediately result in high losses due to the small mode field diameter used in the interface.

In order to solve this, PHIX has a partnership with TEEM Photonics. They have an outstanding 20 year track record when it comes to manufacturing components based on their glass ion exchange process (ioNext). Early products were introduced in the market as early as the late 90s and were used for the Fiber To The Home (FTTH) rollout. Glass splitters provided a very low loss with this technology. Fiber attachment to these devices was straightforward since the mode was matching very nicely with the single mode fibers used in the telecommunication industry.

The ion exchange process is a lithographic panel scale process which allows a very well-defined position of the waveguide with respect to the surface. Due to this lithographic accuracy the chips can be easily aligned to an integrated photonics chip which has multiple channels, without sacrificing a loss penalty due to core misalignments. Also, due to the Ion Exchange process, the amount of diffusion can be tuned locally. Therefore, the refractive index profile can be optimized and allow for the manufacturing of spot size converters.

However great this sounds, there is one more additional assembly required to assemble these SSCs effectively to fiber arrays. This is where PHIX can use its fiber array manufacturing knowledge and its strong background in photonics assembly. A proprietary process has been developed and allows the SSCs to be effectively terminated to a fiber array like a photonics chip.

Also, this terminated SSC can be polished under various angles. In our initial testing we demonstrated that we can polish these under an angle of 45 degrees. With this in hand, one has an excellent polarization maintaining probe which can be used for wafer scale testing of silicon photonics by using an orthogonal coupling scheme. The silicon makes the prober very durable, and the waveguide location just under the surface together with the mode adaption make sure to have a very stable low loss interface to probe the Photonic Integrated Circuits (PICs).


  • Low loss taper from 3,1 x 4,1 microns to single mode fiber
  • Conversion loss less than 1,5dB
  • Polarization maintaining
  • 127 or 250 pitch
  • 1, 4, 8 and 16 fibers available off the shelf
  • Polishing angles for edge or surface coupling
  • FC, LC or MPO connector interface
  • UPC or APC connector polishing style


  • Scalable volume demands ranging from the first prototypes to large quantities
  • Photonic Integrated Circuit compatible
  • High Polarization Extinction Ratio (PER)
  • Accurate core pitch position
  • Customized solutions available
  • Compact design