Edge interference filter for optical communication transmission in wavelength-division multiplex

Claim 1

In an edge interference filter for optical communication transmission in wavelength-division multiplex, said filter comprising a layer sequence arranged between adjacent outer media, said layer sequence being composed of alternately arranged layers with high index of refraction and layers with low index of refraction wherein the two outer layers of the layer sequence adjacent to the outer media are layers of the high index of refraction, the improvements comprising said layer sequence being composed of a total of 23 alternate layers, each of the high index of refraction layers being composed of a material having an index of refraction of 2.08±0.05, each of the low index refraction layers being composed of a material having an index of refraction of 1.45±0.05, the individual layers have an optical layer thickness standardized at 1/4 wavelength of an attenuation band center wavelength of 1260 nm at a 20° angle of incidence with the thickness of the layers having an allowable deviation of at most 2%, said layers having the following thicknesses, the first and twenty-third layers having a thickness of 1.146 of the standardized thickness, the second and twenty-second layers having a layer thickness of 0.909 of the standardized thickness, the third and twenty-first layers having a layer thickness of 1.039 of the standardized thickness, the fourth and twentieth layers having a layer thickness of 0.932 of the standardized thickness and the remaining fifth through nineteenth layers having a constant thickness of one standardized thickness.