Does an EDFA Contain an Optical Circulator?

Erbium-doped fiber amplifiers (EDFAs) are special types of optical amplifiers meant to provide discreet amplification. Discreet amplifiers are often used as boosters, pre-amplifiers, or in-line amplifiers. Sometimes, they are also used to compensate for the loss of additional elements such as DCM, which is often located between the fiber spans. How is a typical EDFA