| 摘要 |
PROBLEM TO BE SOLVED: To reduce the overall size without spoiling the signal separation performance of a variable wavelength optical filter of advanced technology for a wavelength multiplex light signal by using a core expansion fiber and a laminate type polarized light separation plate. SOLUTION: When a light beam containing both P- and S-polarized light components is projected from an end surface of the core diameter-increased part 1C of an input fiber 1 and enters an LPS plate (laminate type polarized light separation plate), only the P-polarized light travels straight to pass through a glass substrate 30 and a liquid crystal cell 33, has its optical path changed by a right-angled prism 92, and travels straight in the cell 33, and plate 30 and 25 again to enter an output fiber 3 as a 2nd optical fiber. The S-polarized light, on the other hand, is refracted by a plate 25 and then converted by a 1/2-wavelength plate 14 into P-polarized light, which after passing through the cell 33 and a prism 12 passes through the cell 33 and plate 14 again and is reconverted into the S-polarized light and then refracted by the plate 25 to enter the output fiber 3. When an electric field is applied from a driving power source 501 to the cell 33 in this state, resonance wavelength varies according to the intensity and a light beam of specific wavelength can be transmitted. |
