The present invention provides an optical amplification system (1) having a plurality of cascade-connected optical amplification units (11), wherein the optical amplification units (11) comprise: a band division unit (111) that divides an optical signal into optical signals of two different bands; a polarized wave division unit (112) that divides the divided optical signals into two polarized wave components orthogonal to each other, an excitation light multiplexing unit (113) that multiplexes excitation light and the optical signals divided by the polarized wave division unit (112); an amplification medium (115) that generates an optical parametric amplification and amplifies the optical signals; an excitation light division unit (117) that divides the excitation light and the optical signals amplified by the amplification medium (115); a polarized wave synthesis unit (118) that synthesizes the two divided polarized wave components; and a band multiplexing unit (119) that multiplexes the two divided bands.

A method for equalization in an access network of passive optical network type. The method includes, for a given optical distribution network connecting a given input port of an optical line termination to a given plurality of optical network units: for at least one of the optical network units of the given plurality, obtaining a distance between the optical line termination and the optical network unit; determining a representative distance associated with the given optical distribution network, according to the one or more distances obtained; determining at least one equalization parameter, according to the representative distance; and equalizing transmission channels within the given optical distribution network, according to the at least one equalization parameter, each of the transmission channels connecting the given port of the optical line termination to one of the optical network units of the given plurality.

A variable optical attenuator (VOA) array is described, which may achieve a power adjustment speed of 1 ms or less for each channel. The VOA array includes: a substrate; and a plurality of VOAs disposed on the substrate, where the plurality of VOAs have trenches therebetween, and a VOA in the plurality of VOAs includes: a phase change material (PCM) layer, where a state of the PCM layer is selectively in a crystalline state, an amorphous state, or a mixed state based on temperature of the PCM layer, and variation of the state of the PCM layer is used for adjusting an output power of an optical signal input into the VOA array; a controller configured to change the temperature of the PCM layer; and a mirror layer configured to reflect the adjusted optical signal of the