Optical signal equalizer for wavelength division multiplex transmission optical fiber device

PURPOSE: To equalize the difference of gain for each wavelength generated at every time when passing an amplifier by using a polarization independent acoustic tuned optical filter(PIATOF). CONSTITUTION: Many optical signals (DFBλ1 to λN) 210 each which has a different wavelength are combined by a wavelength division multiplexer(WDM) 220, and the combined signal is transmitted via an optical amplifier (K) 130. The output signal from the K 130 is supplied to the PIATOF 250. The PIATOF 250 is an output device having two ports. The output of one port is branched by a tap 230. The branched signal is supplied to a demultiplexer 240 and split according to the wavelength, and the split signal is transmitted to a photodetector 260. The photodetector 260 compares the output signals of the PIATOF for each wavelength, and determines an adequate RF power signal to be supplied to the PIATOF from a control device 280. As a result, the signal level for each wavelength of the output signal at one port in the PIATOF is equalized after amplified.