Seed light module for passive optical network

A seed light module for a passive optical network, comprising:

• an optical amplifier to amplify seed light;
• an optical wavelength filter to transmit broadband light, which is output in opposite direction to an output direction of the seed light, at periodic frequency intervals;
• and
• an optical circulating element disposed between the optical wavelength filter and the optical amplifier to circulate light which is spectrum-sliced through the optical wavelength filter to the optical amplifier and forward broadband light from the optical amplifier to the optical wavelength filter.