With the digitalization process, data processing, storage and transmission have been developed in leaps and bounds. Fast-growing data networks require high-efficiency, high-bandwidth, high-reliability, low-cost data transmission media. Compared with traditional electrical interconnections, fiber-based optical interconnections have the advantages of high bandwidth, low loss, long distance crosstalk-free and electromagnetic compatibility.

A number of optical transceivers and fiber optic patch cords to form a set of data communications interconnection system, that is, active fiber optic cable. Compared with the interconnection system composed of independent components (optical transceiver module, fiber optic patch cord) has a higher speed and high reliability, making the system lower cost and easier to maintain.

AOC= Optical Transceiver + fiber optic patch cords

Active optical cable can be divided into three functional parts: optical transmitting part, optical receiving part, and control circuit.

The optical transmitting part contains: VSCEL laser, monitoring diode, driving and control circuit, etc.

Optical transmitting is to transform digital electric signal into optical signal for transmission through optical fiber, mainly including signal modulation, static working point adjustment and automatic power control sub-circuit, with transmitting prohibition and monitoring output function.

Optical reception part: photodiode (PIN), transimpedance amplifier (TIA) and auxiliary circuits.

Optical reception is to convert the weak optical signal in the fiber into an electrical signal, and the transimpedance amplifier (TIA) outputs a limiting electrical signal with no-light alarm function.

Take QSFP+AOC as an example, the two ends of the cable (A end and B end) are QSFP optical module devices, at the A end, the data input Din is an electrical signal, and the electrical signal is converted into an optical signal of a specific wavelength through an electrical-to-optical conversion device (E/O Converter), and the optical signal is input into the optical cable after modulation and coupling; after the optical signal reaches the B end through the optical cable, the optical detection device (O/ E Converter) detects the optical signal and outputs the corresponding electrical signal from Dout. The optical signals are transmitted symmetrically at B and A ends.

Parallel optical interconnection is realized by parallel optical modules and ribbon optical cables. Parallel optical modules are based on VCSEL arrays and PIN arrays with wavelengths of 850nm, suitable for multimode fiber 50/125um and 62.5/125um. In terms of packaging, standard MegArray connectors are used for the electrical interface and standard MTP/MPO ribbon fiber cables for the optical interface. At present, the more common parallel optical modules are 4-way transceiver and 12-way transceiver separation module.