The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
Nov. 14, 1995
Filed:
Jul. 29, 1994
Keiko Takeda, Kawasaki, JP;
Shinya Inagaki, Kawasaki, JP;
Kenji Tagawa, Kawasaki, JP;
Kazuya Sasaki, Kawasaki, JP;
Fujitsu Limited, Kanagawa, JP;
Abstract
An optical fiber amplifier employs an optical fiber and an optical coupler. The optical fiber has a core and a clad. The core has an erbium-aluminum-doped center and an erbium-doped annular section. The optical coupler guides signal light and pump light to the optical fiber, which amplifies the signal light using the pump light. The center of the core corresponds to a section where the field diameter of the signal light overlaps that of the pump light. The annular section is outside the field diameter of the pump light. The amplifier provides a required gain without employing optical parts such as filters. The signal light has a wavelength in the 1.5-micrometer band, and the pump light has a wavelength, in the 1.45-micrometer band, corresponding to the absorption band of erbium. The present invention may further employ pump light having a wavelength in the 0.98-micrometer band. The optical fiber may be doped with erbium and aluminum only in an annular section around the center of the core, to prevent a gain drop near a wave length of 0.98 micrometers.