Optical: systems and elements – Single channel simultaneously to or from plural channels – By partial reflection at beam splitting or combining surface
Reexamination Certificate
1999-03-19
2001-06-26
Epps, Georgia (Department: 2873)
Optical: systems and elements
Single channel simultaneously to or from plural channels
By partial reflection at beam splitting or combining surface
C359S199200
Reexamination Certificate
active
06252719
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to beam splitters and, in particular, to a beam splitter and/or combiner module for a wavelength division multiplex system.
2. Description of the Related Art
In optical fiber transmission systems, it is known to terminate a bidirectionally used optical fiber with what is commonly referred to as a BiDi module which provides an economical and space-conserving termination. The BiDi module, typically disposed at one end of an optical fiber, has a dichroic mirror oriented with respect to the fiber at about 45° incidence and coated to reflect either a 1.3 &mgr;m or 1.5 &mgr;m wavelength.
U.S. Pat. No. 4,431,258 to Fye discloses an optical transmission system having a beam splitter at opposite ends of an optical fiber. Each of the beam splitters has an isosceles right triangular cross section and a multilayer dielectric coating sandwiched therebetween. Each layer of the coating is tuned for quarter-wave operation with 45° incident light at 0.83 &mgr;m. A first beam splitter is oriented with respect to the fiber at 43° incidence and has a high nonpolarizing reflectance at a wavelength &lgr;
2
of 0.85 &mgr;tm and a low loss transmission at a wavelength &lgr;
1
of 0.81 &mgr;m. A second beam splitter is oriented with respect to the fiber at 47° incidence and has a high nonpolarizing reflectance at the wavelength &lgr;
1
and a low loss transmission at the wavelength &lgr;
2
. So arranged, the optical transmission system achieves full duplex communications at 0.81 &mgr;m and 0.85 &mgr;m over a single optical fiber.
U.S. Pat. No. 5,210,643 to Fujii et al. discloses a wave combining apparatus for semiconductor lasers. The combining apparatus includes a first dichroic mirror for combining two orthogonal P-polarized beams of 780 nm and 830 nm to produce a first resultant beam, and a second dichroic mirror for combining two orthogonal S-polarized beams of 780 nm and 830 nm to generate a second resultant beam. The first and second resultant beams are then combined by a polarizing beam splitter prism to form a single waveform for transmission through an optical fiber. According to Fujii et al., this wave combining apparatus is efficient because the dichroic mirrors can be selected to maximize transmission of the polarized beams.
U.S. Pat. No. 5,052,780 to Klein discloses a dichroic beam splitter for use with high power lasers. The beam splitter of Klien has a single uncoated piece of high quality optical glass which separates and rejects a fundamental beam while transmitting the harmonics therethrough.
SUMMARY OF THE INVENTION
A particular advantage of the present invention is that the inventive beam splitter/combiner module can be manufactured at low cost.
Another advantage of the present invention is that the beam splitter/combiner module can separate and/or combine a plurality of signals having more than three different wavelengths.
In a currently presently preferred embodiment of the present invention, the beam splitter/combiner module is connectable to an optical fiber end and is operative for multiplexing and/or demultiplexing a plurality of optical signals having at least three different to wavelengths &lgr;
1
, &lgr;
2
, and &lgr;
3
traveling through the module. The inventive module includes a first dichroic mirror having a low loss transmission over a first preselected range of wavelengths including &lgr;
1
and &lgr;
2
so as to substantially transmit signals having wavelengths &lgr;
1
and &lgr;
2
therethrough and along an optical signal path. The first dichroic mirror also has a high reflectance over a second preselected range of wavelengths including
3
so as to substantially reflect a signal having wavelength &lgr;
3
. A second dichroic mirror, disposed along the optical signal path for receiving the signals transmitted through the first dichroic mirror, has a low loss transmission over a third preselected range of wavelengths including &lgr;
1
so as to substantially transmit the signal at wavelength &lgr;
1
through the second dichroic mirror. The second dichroic mirror also has a high reflectance over a fourth preselected range of wavelengths including &lgr;
2
so as to substantially reflect the signal having wavelength &lgr;
2
.
Other objects and features of the present invention will become apparent from the following detailed description considered in conjunction with the accompanying drawings. It is to be understood, however, that the drawings are designed solely for purposes of illustration and not as a definition of the limits of the invention, for which reference should be made to the appended claims.
REFERENCES:
patent: 4431258 (1984-02-01), Fye
patent: 5048946 (1991-09-01), Sklar et al.
patent: 5052780 (1991-10-01), Klein
patent: 5210643 (1993-05-01), Fujii et al.
patent: 5521733 (1996-05-01), Akiyama et al.
patent: 5600487 (1997-02-01), Klyomoto et al.
patent: 5912910 (1999-06-01), Sanders et al.
patent: 5933260 (1999-08-01), Cao et al.
patent: 5963684 (1999-10-01), Ford et al.
patent: 6034378 (2000-03-01), Shiraishi
patent: 6041072 (2000-03-01), Ventrudo et al.
Epps Georgia
Lucent Technologies - Inc.
Seyrafi Saeed
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