Optical waveguides – With optical coupler – Input/output coupler
Reexamination Certificate
2003-03-13
2004-11-23
Robinson, Mark A. (Department: 2872)
Optical waveguides
With optical coupler
Input/output coupler
C398S079000
Reexamination Certificate
active
06823114
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an optical signal processing apparatus for processing signal light with multiple wavelengths.
2. Related Background Art
An optical signal processing apparatus separates multiplexed signal light with wavelengths into light components of the respective wavelengths and individually outputs the signal light components of the respective wavelengths, or multiplexes signal light components with different wavelengths, which are input for the respective wavelengths, and outputs signal light with multiple wavelengths. Alternatively, an optical signal processing apparatus separates signal light with multiple wavelengths into signal light components of the respective wavelengths, executes certain processing (e.g., loss impartation), then multiplexes the signal light components, and outputs signal light with multiple wavelengths. Such an optical signal processing apparatus is used in an optical communication system as an optical multiplexer, an optical demultiplexer, or a loss filter.
For example, an optical signal processing apparatus makes multiplexed signal light with wavelengths incident on a diffraction grating, separates the signal light into signal light components of the respective wavelengths using a fact that the optical diffraction angle of the diffraction grating changes depending on the wavelength, and outputs the separated signal light components of the respective wavelengths to spatially different optical paths. This optical signal processing apparatus imparts a predetermined loss to the spatially separated signal light components of the respective wavelengths, multiplexes the signal light components of the respective wavelengths, and outputs the multiplexed signal light with the wavelengths. That is, the optical signal processing apparatus operates as a loss filter. As an apparatus of this type, an optical signal processing apparatus disclosed in WO 01/04674A1 is known.
When the optical signal processing apparatus should perform processing for the signal light components of the respective wavelengths, the spatial interval between the optical paths of the signal light components of the respective wavelengths is preferably sufficiently large at the processing position. When the optical signal processing apparatus should multiplex or demultiplex wavelengths, the spatial interval between the optical paths of the signal light components of the respective wavelengths is preferably sufficiently large at the position where the signal light components are input or output for the respective wavelengths. In the latter case, if a fiber collimator is arranged at the position where the signal light components are input or output for the respective wavelengths, the spatial interval between the optical paths of the signal light components of the respective wavelengths must be larger than the outer diameter of the fiber collimator.
SUMMARY OF THE INVENTION
Let &Lgr; be the grating period of a diffraction grating, &lgr; be the wavelength of light incident on the diffraction grating, &bgr;
0
be the incident angle of light on the diffraction grating, and &bgr;
1
be the diffraction angle. At this time, a relation given by
m
&lgr;=&Lgr;(sin &bgr;
0
+sin &bgr;
1
) (1)
holds. In this case, m is the diffraction order. In a signal light wavelength band (1.55 &mgr;m) used in optical communication, the diffraction angle difference with respect to the unit wavelength difference is as small as 0.1 deg
m or less. Hence, when the interval between the optical paths of the signal light components of the respective wavelengths should be sufficiently large after wavelength separation by the diffraction grating, the optical path length from the diffraction grating increases. For this reason, a conventional optical signal processing apparatus is bulky.
The present invention will become more fully understood from the detailed description given hereinbelow and the accompanying drawings which are given by way of illustration only, and thus are not to be considered as limiting the present invention.
Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.
The present invention has been made to solve the above problem, and has as its object to provide an optical signal processing apparatus capable of size reduction.
An optical signal processing apparatus according to the present invention is characterized by comprising (1) wavelength separation means for receiving multiplexed signal light having multiple wavelengths &lgr;
1
to &lgr;
N
(&lgr;
n−1
<&lgr;
n
; N is an integer, 2≦N; n is an integer, 2≦n≦N), separating the multi-wavelength signal light into signal light components of respective wavelengths, and outputting the separated signal light components of the respective wavelengths to spatially different optical paths, and (2) optical path changing means for changing the optical paths of the signal light components of the respective wavelengths output from the wavelength separation means. The optical signal processing apparatus is also characterized in that for a first signal light component (wavelength &lgr;
n−1
) and second signal light component (wavelength &lgr;
n
), which have adjacent wavelengths in the signal light components with the multiple wavelengths, letting G be a position at which the multi-wavelength signal light is wavelength-separated by the wavelength separation means, P
n−1
be a position at which an optical path of the first signal light component is changed by the optical path changing means, L
n−1
be a distance from the position G to the position P
n−1
along the optical path of the first signal light component, and P
n
be a position which is located on an optical path of the second signal light component from the position G to the optical path changing means or on an extended line of the optical path, and separated from the position G by the distance L
n−1
, a distance between the optical paths of the first and second signal light components, which are changed by the optical path changing means, is set to be larger than a distance between the position P
n−1
and the position P
n
.
In this optical signal processing apparatus, when the multiplexed signal light having multiple wavelengths &lgr;
1
to &lgr;
N
is input to the wavelength separation means, the signal light of the multiple wavelengths is separated for the respective wavelengths and output to different optical paths. The optical paths of the signal light components of the respective wavelengths, which are wavelength-separated, are changed by the optical path changing means. With this optical path change, the optical path interval between the signal light components of the respective wavelengths is increased. The signal light components can also propagate in a reverse direction. Even when the degree of optical path separation for the signal light components of the respective wavelengths by the wavelength separation means is low, the optical path interval between the signal light components of the respective wavelengths is increased by the optical path changing means. Hence, the optical signal processing apparatus according to the present invention can be made compact because the optical path after optical path separation for the signal light components of the respective wavelengths by the wavelength separation means can be short.
The optical signal processing apparatus according to the present invention preferably includes a diffraction grating. In this case, letting &Lgr; be a grating period of the diffraction grating, &thgr; be an angle made by a plane p
Sano Tomomi
Suganuma Hiroshi
Takushima Michiko
Tanaka Tatsuhiko
Amari Alessandro
McDermott Will & Emery LLP
Robinson Mark A.
Sumitomo Electric Industries Ltd.
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