Patent ID: 6978064
Filing Date: 2005-12-20
Classification: G02B,H04B

Abstract:
1. A variable optical filter comprising: first and second filter sections connected in series, said first and second filter sections having corresponding first and second filter characteristics respectively with transmissivity of each filter characteristic changing periodically along an optical frequency axis, said first and second filter characteristics each having variable transmissivity and capability of being shifted in an optical frequency axis direction, said first and second filter characteristics being set within a common variable range in the optical frequency axis direction; and a control section for, when the filter characteristic of one of said first and second filter sections is required to shift in the optical frequency axis direction to exceed the variable range, relatively controlling the filter characteristics of said first and second filter sections with respect to each other such that a switching is performed from said one of said first and second filter sections to the other of said first and second filter sections, provided that the overall combined filter characteristic of said first and second filter sections becomes constant, to thereby allow the filter characteristic of said other of the first and second filter sections to shift in the optical frequency axis direction instead of the filter characteristic of said one of the first and second filter sections.