Coupler add/drop node WDM network architecture with periodic cleanup

For an optical network having an optical fiber carrying signals of a plurality of wavelengths, each wavelength defining a communication channel for said optical network, a combination comprising:

• a first optical amplifier stage having an input terminal for connection to said optical fiber and an output terminal;
• a second optical amplifier stage having an input terminal and an output terminal connected to said optical fiber;
• a wavelength blocker unit connected to said output terminal of said first amplifier stage and said input terminal of said second amplifier stage, said wavelength blocker unit preventing signals of one or more predetermined wavelengths from passing from said first optical amplifier input terminal to said second optical amplifier output terminal;
• and
• a pump connected to said first and second optical amplifier stages;
• whereby signals not of said one or more predetermined wavelengths are amplified in said optical fiber and signals of said one or more predetermined wavelengths are blocked.