Optical Connectivity Offers I/O Options

By Robert Hult | May 05, 2014

Optical connectivity now offers I/O options, such as Molex’s optical interfaces designed to support up to 400Gb/s.

Optical I/ODemand for higher port density and bandwidth has stimulated the introduction of high-performance optical I/O connectors that support up to 400Gb/s links. Manufacturers such as Avago Technologies, FCI Electronics, Samtec, and TE Connectivity offer a variety of optical alternatives to copper, giving design engineers more packaging and performance options than ever before. “Silicon photonics” has become a hot buzzword in the industry.

The recent Optical Fiber Communication Conference (OFC) provided the perfect venue for Molex to introduce three new products to its extensive line of optical interconnects.

Active optical cables are proving to be an effective alternative to standard copper interconnects. They mate directly with the standard panel interface, but convert the electrical signals to optic using devices mounted in the cable connector. High-speed signals are transmitted over thin optical cable to the far end where signals are converted back to electronic signals. AOCs offer improved signal integrity, longer reach, reduced power consumption, improved data security, and much-reduced cable bulk.

Molex optical I/O 4x25 Gb



The new Molex 4X25 Gb AOC operates at 100Gb/s and is packaged in a standard QSFP connector. This interface is compliant with Infiniband EDR as well as 10G, 40G, and 100G Ethernet standards.


Molex optical I/O 400gbsA new 400Gb/s (16X25 Gb) pluggable interface is compliant with the CDFP MSA. The zCD AOC transmits 28Gb/s over 16 bi-directional channels that enable the design of line cards with up to five terabytes of I/O.

Interest continues to grow in the ability to optically launch gigabit signals from any location on a line card. Tiny optical ribbons can be run to either the backplane for linking to other line cards or to the front panel, where smaller pluggable I/O connectors can dramatically increase panel density.

Molex optical I/O 200gbsMolex announced a 200Gb/s mid-board optical transceiver with output options of 1X200 Gb/s or 2X100 Gb/s.

The far end can be terminated in an MPO or expanded-beam connector, which offers much improved panel density.

The design philosophy behind these new Molex products differs somewhat from competitive connectors on the market today. The Coolbit optical transceiver technology from TE Connectivity encodes data by directly modulating the output of a VCSEL, which is coupled to a multi-mode fiber. The Molex design utilizes a separate modulator that shutters a laser that is continually on. The laser output can be scaled to match the requirements of a specific application, providing more design flexibility. Optic signals are coupled to single-mode fiber that enables link distances to 4Km while consuming only 1.5W per 100Gb. All of the elements of the Molex transceiver (except the light source) are integrated into a single chip to simplify manufacturing and reduce cost. This design also results in exceptionally low bit error rates (BER) of 10-18.

All of these new Molex optical products are being marketed under the QuatroScale brand name. They address the continuing evolution of Ethernet and InfiniBand data rates and focus on applications in high-performance server and storage equipment.

Optical I/O link bandwidth chart

Molex also announced support for the new MXC fiber optic interface with its VersaBeam expanded-beam ferrule technology and single-mode silicon photonic active optical products. MXC plugs and panel-mount receptacles feature up to 64 optical fibers in an envelope 15% smaller than standard MPO connectors.

It may be many years, if ever, before high-speed copper I/O connectors are seriously threatened by optic alternatives, but the emergence of new generations of optical interfaces that offer some highly attractive features will begin to chip away at the dominance of copper in select applications.

Robert Hult, Market Director, Bishop & Associates, Inc.

Robert Hult
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