An aggregation device, an optical module, and an optical network system. The aggregation device includes: a first port, configured to receive a plurality of downlink coupled optical signals in different wavelengths; a first component, configured to split the downlink coupled optical signal to form a plurality of different downlink optical signals, and aggregate the plurality of received uplink optical signals into one uplink coupled optical signal and output the uplink coupled optical signal to a third port; a plurality of second ports, configured to output the plurality of downlink optical signals to corresponding bidirectional access optical modules among a plurality of bidirectional access optical modules respectively, receive a plurality of uplink optical signals in different wavelengths, and output the uplink optical signals to the first component; and the third port, configured to output the uplink coupled optical signal to the core optical module.