Two transceiver formats for 400 Gigabits

Fiber-optic signal transmission is reaching a new dimension: 400 Gigabits per second (400 G). The subject is currently top of mind in the industry.

400-Gigabit chips are now commercially available. The market offers two transceiver formats: QSFP-DD and OSFP. They continue conventional connectivity with plug-in active connections in the front panel of a switch. Frequency, modulation, and transmission rates are rising. The form factor is becoming more compact. Energy consumption is falling.

COBO: moving connectivity to the circuit board

The Consortium for On-Board Optics (COBO) is proposing a more radical change:

  • Transceivers, which need a lot of space, should be moved from the housing to the board.
  • The copper path between electronics and interface is reduced.
  • The transmission rate increases.
  • Internal glass fibers establish the connections with multi-fiber adapters in the housing.

This would mean many more fiber connections could be accommodated in the front panel – a prerequisite for more optical channels and more data transmission.

Manufacturers still have to take a few technological hurdles before the idea is ready for serial production. As a COBO member, R&M is committed to this technology.

Does Quantum leap with expanded beam connectors?

A crucial question is how masses of multi-fiber connections and connectors in the front panel can be best connected and maintained. In the conventional parallel optical connection method, all-fiber stubs would have to be pressed together tolerance free with high pressure. The many uninsulated fiber stubs would be very difficult to clean.

Expanded beam connectors would be an alternative. Microlenses on the fiber stubs ensure the perfect transition of light, called the expanded beam. The advantages:

  • All that is needed is gentle contact pressure or rather physical contact is not needed at all.
  • The coupling mechanism can be simplified.
  • The packing density in the front panel can be increased.
  • The lenses tolerate minor faults and are robust.
  • They are insensitive to dirt and require virtually no cleaning.

R&M estimates that expanded beam connectors will be a pioneer for the era of on-board optics.