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. 24, 1998
Filed:
Jan. 22, 1997
Yuji Tamura, Sapporo, JP;
Hiroyuki Itou, Sapporo, JP;
Tsukasa Takahashi, Sapporo, JP;
Michikazu Shima, Kawasaki, JP;
Yumiko Kawasaki, Kawasaki, JP;
Kazuo Yamane, Kawasaki, JP;
Fujitsu Limited, Kanagawa, JP;
Abstract
Spontaneous emission occurring in association with direct optical amplification using an erbium-doped optical fiber is modulated with an auxiliary signal, such as a supervisory signal, for transmission of the auxiliary signal. In a first aspect of the invention, the output of an optical amplifier is passed through a variable optical band-pass filter whose transmission characteristic is varied in accordance with the auxiliary signal, to modulate the spontaneous emission component contained in the optical amplifier output. In a second aspect of the invention, the output of the optical amplifier is separated by an optical branching device into a main optical signal and part of the spontaneous emission. The separated spontaneous emission component is modulated by being passed through a variable optical band-pass filter whose transmission characteristic is varied in accordance with the auxiliary signal, and then, the modulated spontaneous emission component is wavelength-division multiplexed with the main optical signal.