Loading patent…
AssigneeShowa Electric Wire & Cable Co., Ltd.
InventorsMasaru Watanabe, Eiji Matsuyama, Akiyoshi Naruse, Yuichi Murakami, Kenichi Muta, Toyomitsu Yamamoto
Estimating the term…
An optical attenuator which provides almost the same degree of attenuation even when the difference in wavelength of two different kinds of input optical signals is small. Another optical attenuator is provided with a dopant concentration in a technically realizable range which increases the difference in optical attenuation of two different kinds of input optical signals. Almost the same degree of attenuation may be obtained even when the difference between wavelengths is small by canceling the wavelength dependency of attenuation of the dopant by raising the refractive index of an axially central portion of the core as compared to that of the peripheral portion of the core and by taking into account the type and area of the dopant and the ratio of the difference Δ2 between the refractive indexes of the cladding and the axial portion of the core and the difference Δ1 between the refractive index of the cladding and the refractive index of the peripheral portion, i.e., Δ1/Δ2. On the other hand, the difference of attenuation is increased while suppressing the concentration of dopant to the realizable range.
An optical attenuator in the form of a single mode optical fiber for receiving an optical signal, attenuating the optical signal and outputting the attenuated optical signal, said optical attenuator comprising a core containing a dopant which attenuates the optical signal more when its wavelength is longer, said dopant being contained only in a dopant area limited to a centermost portion of said core, said core comprising said centermost portion and a peripheral portion contiguous with said centermost portion and free of dopant, said core having a refractive index at said centermost portion greater than that of said peripheral portion, said optical fiber having a mode field for single mode transmission of the optical signal inclusive of said centermost and peripheral portions of said core.
An optical attenuator in the form of a single mode optical fiber for receiving an optical signal, attenuating the optical signal and outputting the attenuated optical signal, said optical attenuator comprising a core containing a dopant which attenuates the optical signal more when its wavelength is shorter, said dopant being contained only in a dopant area limited to a peripheral portion of said core, said core comprising a centermost portion free of dopant and said peripheral portion contiguous with said centermost portion, said core having a refractive index at said centermost portion greater than that of said peripheral portion, said optical fiber having a mode field for single mode transmission of the optical signal inclusive of said centermost and peripheral portions of said core.
An optical attenuator in the form of a single mode optical fiber for receiving an optical signal, attenuating the optical signal and outputting the attenuated optical signals, said optical attenuator comprising a core containing a dopant which attenuates the optical signal more when its wavelength is longer, said dopant being contained only in a dopant area limited to a peripheral portion of said core, said core comprising a centermost portion free of dopant and said peripheral portion contiguous with said centermost portion, said core having a refractive index at said centermost portion greater than that of said peripheral portion, said optical fiber having a mode field for single mode transmission of the optical signal inclusive of said centermost and peripheral portions of said core.
Dependencies are inferred from the claim text.