OPTICAL FIBER TYPE FILTER WITH SINGLE TRANSMISSION LINE SPECTRUM

PROBLEM TO BE SOLVED: To provide a compact and low-cost ultra-narrow band optical filter capable of providing the number of lines similar to those of a conventional circuit element of a highest level.SOLUTION: An optical fiber-type filter includes: an optical fiber Bragg grating FBG drawn inside a first optical fiber; a wide band mirror WM configured at an end face of a second optical fiber; and a connecting component for connecting them. Alternatively, an optical fiber-type filter includes an optical fiber Bragg grating FBG drawn inside the optical fiber, and a wide band mirror WM configured at an end face of the optical fiber.