Quantum Leap with Expanded Beam Connectors?
Fiber-optic signal transmission is reaching a new dimension: 400 Gigabits per second. The subject dominated the specialist congress Optical Fiber Communication Conference and Exhibition (OFC) 2018 in San Diego.
400G chips will be available commercially from the end of 2018. The two market-ready transceiver formats – QSFP-DD and OSFP – are the logical continuation of conventional connectivity with plug-in, active connectors on the front panel of a switch. Frequency, modulation and transmission speed will increase, the form factor will be more compact, energy consumption will fall.
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 the electronics and the interface will thus be reduced, the transmission speed increased. Internal glass fibers establish the connections with miniaturized multi-fiber adapters in the housing front.
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 this idea is ready for serial production. As a COBO member, R&M is on the cutting edge of technological development.
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.
R&M is developing its own technology called expanded beam technology. Micro lenses on the fiber stubs ensure the perfect transition of light. 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.
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