Popular optics for FTTx are bidirectional optics also known as BiDi’s.  Solid Optics offers a large line of BiDi optics ranging from 100Mbit to 10G.  Certain BiDi optics are capable of distances up to 150km.  BiDi’s normally come in pairs; an upstream optic and a downstream optic.  For example, an ‘Upstream’ optic might transmit on 1310nm and receive on 1550nm, where its opposite ‘Downstream’ optic transmits on 1550nm and receives on 1310nm.

Fiber to the home usually only requires one side as the customer-premises equipment typically has the other side built-in, leading to the development of the popular CSFP (Compact Small Form-factor Pluggable) optic which combines two BiDis in one SFP.  CSFPs are a very cost-effective solution because you can double the amount of subscribers ‘attached’ to a switch.