Optical waveguides – With optical coupler – Particular coupling structure
Reexamination Certificate
2002-06-21
2004-11-16
Chowdhury, Tarifur R. (Department: 2871)
Optical waveguides
With optical coupler
Particular coupling structure
C385S047000, C385S088000, C385S129000
Reexamination Certificate
active
06819840
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an optical transmitting/receiving module to be used in optical fiber communication and to a method for manufacturing the same.
2. Description of the Related Art
In recent years, attention has been focused on optical fiber communication, by which an information of large capacity can be transmitted at high speed and with low loss and which uses optical fiber instead of metallic cable. With the progress of technique, there are now strong demands on optical devices, which can be produced at lower cost and are provided with high functions for high-speed transmission. For instance, efforts have now been made to develop an optical communication system, by which optical bidirectional transmission in outgoing and incoming directions with different wavelengths of &lgr;1 and &lgr;2 can be achieved using a single optical fiber. To produce an optical module of this type, it is necessary to use a technique to separate the wavelength of a light emitting element from that of a light receiving element and to integrate components with optical multiplexing function.
Description will be given below on a typical example of a conventional type optical bidirectional module. In the past, a structure combining an optical waveguide with a wavelength division multiplexing (WDM) filter has been commonly used to separate a signal of receiving wavelength &lgr;1 from a signal of transmitting wavelength &lgr;2.
FIG. 11
shows a conventional structure of a WDM optical bidirectional module using optical waveguide disclosed in JP-A-11-68705. On a Si substrate
103
, optical waveguides
102
(
102
a
,
102
b
,
102
c
) are formed in star-like arrangement with a WDM filter
107
at the center. To an end of each of the optical waveguides
102
a
,
102
b
and
102
c
, a light emitting element
105
, a light receiving element
106
, and an optical fiber
101
are aligned by 2-dimensional high-accuracy alignment to achieve optical coupling of incident light with exit light. The alignment of the light emitting element
105
and the light receiving element
106
is generally performed by using alignment markers, which are formed in advance with high accuracy on the Si substrate
103
.
An output light with the wavelength of &lgr;2 of the light emitting element
105
is transmitted via the optical waveguide
102
a
and is reflected by the WDM filter
107
. Then, it passes through the optical waveguide
102
c
and is guided into the optical fiber
101
. For the purpose of achieving optical coupling of end surfaces of the core of the optical fiber
101
and the optical waveguide
102
c
, a V-shaped groove fabricated with high accuracy is formed on the Si substrate
103
with respect to the position of the optical waveguide
102
. Then, the optical fiber
101
is aligned along the V-groove and fixed. On the other hand, a light signal with the wavelength of &lgr;1 transmitted from the optical fiber
101
is transmitted via the optical waveguide
102
c
and passes through the WDM filter
107
, and it is received by the light receiving element
106
via the optical waveguide
102
b
. The light receiving element
106
is designed to have such a structure that it can receive the light when the light enters from lateral side of the chip.
The conventional module as described above have the following problems: The conventional module has the optical waveguide
102
, and it requires complicated process not only to form the V-groove and the alignment markers
108
on the Si substrate
103
but also to provide the optical waveguide
102
with high accuracy. Further, the optical wave guides
102
a
,
102
b
and
102
c
are formed in star-like arrangement with the WDM filter
107
at the center. This means that the Si substrate
103
must have larger size, and it is difficult to produce the Si substrate
103
at low cost. Also, it is difficult to produce the module in small size.
The light receiving element
106
has such a structure that the light from the optical waveguide
102
b
enters side surface of the element of the chip. The optical waveguide
102
b
must be aligned with the light receiving element
106
with high accuracy in the order of 1 to 2 &mgr;m. In order to efficiently arrange the light receiving element
106
and the light emitting element
105
on the Si substrate
103
, it is necessary to use high-temperature soldering reflow process. For this purpose, a resin having high heat-resistant property should be adopted for fixing optical components. Also, it is necessary to design the module with expensive ferrule to achieve reflow arrangement.
SUMMARY OF THE INVENTION
To solve the above problems in the conventional type module, it is an object of the present invention to provide a small size and inexpensive optical transmitting/receiving module without the need to use optical waveguide, which requires complicated process and larger area.
Also, it is another object of the present invention to provide a method for manufacturing an optical transmitting/receiving module, which can be produced by simplified manufacturing process.
To attain the above object, the optical transmitting/receiving module of the present invention comprises a substrate where there are provided a V-groove running in linear direction and a groove crossing said V-groove obliquely at an end of the V-groove, an optical fiber core is arranged to the end of said V-groove, a wavelength selective filter or a half-mirror is provided in said groove, and a light emitting element and a light receiving element are arranged respectively in transmitting direction and reflecting direction of the wavelength selective filter or the half-mirror.
By the above arrangement, it is possible to provide a small and inexpensive wavelength multiplexing optical transmitting/receiving module or a one-wavelength optical transmitting/receiving module without the need to use optical waveguide, which requires complicated manufacturing procedure.
According to another aspect of the present invention, an optical transmitting/receiving module as described above is provided, wherein a side surface of said groove runs in vertical direction, and said light receiving element is designed as end surface incident type.
By this arrangement, it is possible to improve optical coupling of the light receiving element and the optical fiber.
According to another aspect of the present invention, an optical transmitting/receiving module as described above is provided, wherein a side surface of said groove runs in oblique direction, and a second wavelength selective filter to shut off only wavelength of said light emitting element is arranged between said light receiving element and said wavelength selective filter.
By the arrangement as described above, it is possible to reduce light leakage of the light receiving element from the light emitting element. Also, the light receiving element, not of waveguide type but of front surface or rear surface incident type, can be used.
According to another aspect of the present invention, an optical transmitting/receiving module as described above is provided, wherein a light reflection surface of said wavelength selective filter or the half-mirror is fixed on side surface of the groove positioned opposite to the end surface of the optical fiber core.
By this arrangement, it is possible to accurately define the position of the wavelength selective filter or the half-mirror and to improve optical coupling efficiency to the light receiving element. Also, it is possible to increase width of the vertical groove or the oblique groove to a width greater than the thickness of the filter or the like, and this makes the insertion of the filter and the like much easier.
According to another aspect of the present invention, an optical transmitting/receiving module as described above is provided, wherein a light reflection surface of said wavelength selective filter or the half-mirror is brought into contact with and fixed on the side surface of said groove positioned opposite to the end sur
Asano Hiroaki
Tohgoh Hitomaro
Caley Michael H
Chowdhury Tarifur R.
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