Fibre Cables

For high-bandwidth applications and longer distances, fiber optic cables transmit data using light pulses. They offer superior speed, security, and are immune to electromagnetic interference, making them ideal for high-speed network connections and inter-rack communication.

Fiber Optic Cables:-

A technology that uses glass (or plastic) threads (fibers) to transmit data. A fiber optic cable consists of a bundle of glass threads, each of which is capable of transmitting messages modulated onto light waves. ... Fiber optic cables have a much greater bandwidth than metal cables.

For example, Active Optical Cable (AOC) is a cabling technology that accepts same electrical inputs as a traditional copper cable, but uses optical fiber “between the connectors”. AOC uses electrical-to-optical conversion on the cable ends to improve speed and distance performance of the cable without sacrificing compatibility with standard electrical interfaces.

Figure 1: The following sample picture shows a 40Gb/s QSFP+ Active Optical Cable Assembly.

Take a even closer examination and we can see that the active optical cable (AOC) assembly is actually composed of 4 functional parts.

1. The “High-density QSFP+ connector”. This is the SFF-8436 electronic connector which can be plugged into a router or switch.
2. The “4-Channel full-duplex active optical cable transceiver”. This optical transceiver is embedded inside the shell so you cannot see it. This optical transceiver part is responsible for opto-electro (O-E) and electro-opto (E-O) conversion.
3. The MPO optical connector (the black part). This connector is permanently attached to the shell and fiber. This permanent attachment shields the optical interface from the end user and also from environmental contaminants.
4. The ribbon optical fiber cable (this picture shows a yellow jacket single mode fiber, but multimode fiber models are also available).

The above product has four single mode fiber optic transceivers per end, each operating at data rates from 1 to 10.3125 Gb/s and supporting a reach up to 4,000 meters. This active optical cable is electrically compliant with the SFP+ interface and supports InfiniBand, Ethernet, Fibre Channel, Myrinet, and other protocols.

So the basic idea of AOC is to embed the active optical transceiver components into the electronic connector instead of using separate optical transceiver and pluggable fiber cable. (since the cable is permanently attached).

There is a more fundamental reason for the invention of AOC products. This is explained in the following section. Read more..