BIDIRECTIONAL ADD/DROP MULTIPLEXER

PURPOSE: A bidirectional add/drop multiplexer is provided to intercept a relative intensity noise and prevent a collision between a forward optical signal and a backward optical signal by removing or adding channels from or to the forward optical signal and the backward optical signal. CONSTITUTION: A forward arrayed optical fiber waveguide grating(37) is used for demultiplexing an inputted forward optical signal each channel, removing or adding channels from or to the demultiplexed channels, and multiplexing the increased or the reduced channels. A backward arrayed optical fiber waveguide grating(38) is used for demultiplexing an inputted backward optical signal each channel, removing or adding channels from or to the demultiplexed channels, and multiplexing the increased or the reduced channels. The first circulator(36) is used for inputting the forward optical signal into the forward arrayed optical fiber waveguide grating(37) and outputting the backward optical signal of the backward arrayed optical fiber waveguide grating(38) to an optical fiber. The second circulator(39) is used for inputting the backward optical signal into the forward arrayed optical fiber waveguide grating(37) and outputting the forward optical signal of the forward arrayed optical fiber waveguide grating(37) to the optical fiber.