Construction, background and applications of optical nonreciprocal dev
ices are discussed. Operation of optical isolators and circulators bas
ed on Faraday polarization rotation is analyzed. Applications of the n
onreciprocal devices for multipass amplifiers are presented. Construct
ion of polarization independent circulators is discussed including an
all fiber circulator and application of the circulators for fiberoptic
s communications is included.