| 摘要 |
<p>PROBLEM TO BE SOLVED: To provide a variable-spectrum optical filter which is suitably used even when the gain spectrum of an optical amplifier varies and so on. SOLUTION: The optical filter 1 is provided with a polarization beam splitter 21, a 1/2-wavelength plate 31, a Faraday rotator 41, a wavelength plate 51, a 1/2-wavelength plate 32, and a polarization beam splitter 22 in order from an input port 11 to an output port 12. The Faraday rotator 41 is provided on both a 1st path P1 and a 2nd path P2 and can rotate the planes of polarization of light on the 1st path P1 and light on the 2nd path P2 by an angleθ. The wavelength plate 51 is provided on both the 1st path P1 and 2nd path P2 , and varies the polarization states of the lights outputted from the Faraday rotator 41 to the 1st path P1 and 2nd path P2 respectively according to the wavelength and outputs them.</p> |
