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. 28, 1995
Filed:
Apr. 18, 1994
Tatsuya Shiragaki, Tokyo, JP;
Takahiro Shiozawa, Tokyo, JP;
Syuji Suzuki, Tokyo, JP;
Masahiko Fujiwara, Tokyo, JP;
NEC Corporation, Tokyo, JP;
Abstract
An apparatus and a method for performing hitless switching between optical transmission lines such as optical fiber circuits are provided. An optical switch or optical switching network having input terminals and output terminals for selecting optical signals inputted to the input terminals to the output terminals with a selection ratio which can be varied continuously is used. An optical signal converter for generating an optical signal of light which does not interfere with another optical signal is attached to the optical switch. Further, a signal loop interconnecting one of the output terminals of the switch and the input of the optical signal converter is provided. When hitless switching between two optical transmission lines is performed, the same information signal is first inputted to the two transmission lines on the transmission side, then the optical signal from the two lines are transmitted to one of the output terminal (aimed output terminal) of the switch and another output terminal connected to the signal loop. The phase difference between the optical signals is detected and adjusted, and the optical switch is controlled so that the optical signal to be selected at the aimed output terminal is varied to the signal passing through the signal loop.