Optical waveguides – With optical coupler
Reexamination Certificate
2000-01-27
2001-03-13
Ullah, Akm E. (Department: 2874)
Optical waveguides
With optical coupler
Reexamination Certificate
active
06201904
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to an optical demultiplex circuit for demultiplexing signal light multiplexed at a small wavelength interval.
In a narrow-band multiwavelength multiplex transmission system that constructs a large-capacity transmission system, an optical demultiplex circuit for demultiplexing signal light multiplexed at a small wavelength interval is essential. Such an optical demultiplex circuit is formed by combining an AWG (Arrayed Waveguide Grating), dielectric multilayered filter, fiber Bragg grating, chirped fiber grating, and optical circulator.
However, an AWG is generally expensive, has a large insertion loss of about 6 dB, and requires a temperature control circuit. A dielectric multilayered filter or a chirped fiber grating has large side lobes and, generally, dependency on temperature. In addition, when an optical circulator and a fiber Bragg grating are combined, the arrangement for demultiplexing a number of wavelengths becomes complex.
Furthermore, in use of an output from a pumping laser source used for an optical amplifier using a fiber doped with rare earth elements, the upper limit of the number of wavelengths is about 30 to obtain a gain of 25 dB. To solve this problem, polarized wave synthesis or wavelength multiplex of the pumping laser source, and use of a solid-state laser source have been proposed. However, these methods make the apparatus very expensive and bulky.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide an optical demultiplex circuit that solves the temperature dependency of demultiplexed wavelengths used in a narrow-band multiwavelength multiplex transmission system.
In order to achieve the above object, according to the present invention, there is provided an optical demultiplex circuit comprising an optical circulator having a first port for receiving an optical signal, a second port for outputting the optical signal input to the first port, and a third port for outputting the optical signal input to the second port, first reflection means for selectively reflecting optical signals output from the second port and outputting the optical signals to the second port, the first reflection means having a wide reflection wavelength band and side lobes, and second reflection means, inserted between the second port and the first light reflection means, for reflecting, of the optical signals output from the second port, only optical signals in a narrow wavelength band corresponding to the side lobes of the first light reflection means.
REFERENCES:
patent: 5555118 (1996-09-01), Huber
patent: 5579143 (1996-11-01), Huber
patent: 5706375 (1998-01-01), Mihailov et al.
patent: 5754718 (1998-05-01), Duck et al.
patent: 5812306 (1998-09-01), Mizrahi
McGinn & Gibb PLLC
NEC Corporation
Ullah Akm E.
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