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. 27, 1990
Filed:
Dec. 22, 1989
Kazuhisa Kaede, Tokyo, JP;
NEC Corporation, Tokyo, JP;
Abstract
The invention relates to an optical wavelength drop-and-insert device including two sets of input/output optical fibers attached to two terminals on each of a first and second polarization beam splitter. The first polarization beam splitter splits incoming light into two linearly orthogonal polarizations which are transmitted via a first and second polarization preserving fiber through a first and second quarter wave plate for changing the subject beams into circular polarization. An optical filter is included to transmit or reflect light from the quarter wave plates according to a wavelength based transmission/reflection characteristic. The second polarization beam splitter then acts as a combiner for the circularly polarized light which is received via a third and fourth polarization preserving fibers and then is transmitted via an output optical fiber. The second polarization beam splitter splits incoming light into two orthgonal polarizations via an incoming optical fiber for two way operation. A second embodiment of the invention uses a first and second optical filter which can be a Fabry Perot or Bragg diffraction grating type optical fiber.