Optical waveguides – With optical coupler – Particular coupling structure
Reexamination Certificate
2001-03-28
2002-09-24
Ngo, Hung N. (Department: 2874)
Optical waveguides
With optical coupler
Particular coupling structure
C385S014000, C385S083000
Reexamination Certificate
active
06456767
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention concerns a planar-mounted optical waveguide transmitter-receiver module, in which silicon or other substrates, separated into a plurality of substrates, and an optical waveguide (planar lightwave circuit) substrate (hereafter “PLC substrate”), are hybrid-integrated.
2. Description of Related Art
Optical terminal devices for use in optical subscriber systems are subjected to such demands as smaller integration sizes, multi-functionality, and reduced prices. Optical modules which optical waveguides as devices effective for satisfying such demands are coming into widespread use. Conventional silicon platform structures, in which optical waveguides and silicon substrates are united, have problems which include complexity of manufacturing processes, and limitations on the manufactured quantity per unit wafer. For this reason, various planar-mounted optical waveguide transmitter-receiver modules in which silicon substrate and PLC substrate are hybrid-integrated have been proposed. Below, the structure of conventional optical waveguide transmitter-receiver modules is explained, referring to
FIGS. 1 through 3
.
FIG. 1
is a perspective view of an optical waveguide transmitter-receiver module, representing conventional synchronous-transfer mode passive optical networks (hereafter “STM-PON”) and &pgr;-PON systems.
This optical waveguide transmitter-receiver module has a silicon substrate
1
, and an optical waveguide layer
2
is formed on this silicon substrate
1
. The optical waveguide layer
2
is formed by, for example, deposition of quartz glass by sputtering methods, and execution of vitrification processing of this deposited layer by means of high-temperature annealing. In this way, the optical waveguide layer
2
and silicon substrate
1
are formed as a unit to constitute the silicon platform substrate. A dual-branching optical waveguide
3
is formed within the optical waveguide layer
2
, for use in bidirectional communication. The optical waveguide
3
has entry and exit end faces
3
a
to
3
d
, and a groove is cut in the branch part
3
e
, and a wavelength-selection filter embedded therein. The device with this filter
4
removed is &pgr;-PON device.
On the silicon substrate
1
, a semiconductor laser or other light emitting element
5
and photodiode or other photo-receiving element
6
are fixed in place, by soldering or other means, to oppose the end faces
3
a
,
3
b
of the optical waveguide. The module is designed to enable the connection of optical fibers to the end faces
3
c
,
3
d
of the optical waveguide
3
by means of optical connectors.
For example, in an optical waveguide transmitter-receiver module for use in STM-PON systems, a light emitting element
5
and photo-receiving element
6
operate at different times (with different timing). When the light emitting element
5
operates, light is emitted from this light emitting element
5
, and this light is incident on the end face
3
a
of the optical waveguide
3
. Light incident on the end face
3
a
is transmitted within the optical waveguide
3
, is wavelength-selected by the filter
4
provided at the branch part
3
e
, and is, for example, emitted from the end face
3
c
and sent to an optical fiber via an optical connector. On the other hand, light sent from an optical fiber is incident on, for example, the end face
3
c
via an optical connector. The incident light is wavelength-selected by the filter
4
, and emitted from the end face
3
b
. The emitted light is received by the photo-receiving element
6
, converted into an electrical signal, and output. Light of different wavelengths sent from an optical fiber, after incidence on the end face
3
c
, is wavelength-selected by the filter
4
and emitted from the end face
3
d.
FIG. 2
is a perspective view of an optical waveguide transmitter-receiver module compatible with a conventional asynchronous-transfer mode passive optical network (asynchronous transfer mode PON, hereafter “ATM-PON” systems).
This optical waveguide transmitter-receiver module for ATM-PON systems has nearly the same optical component configuration as in
FIG. 1
, but the shape of the optical waveguide
3
A formed within the optical waveguide layer
2
, and the fixed positions of the emissive element
5
and photo-receiving element
6
, are different from those of FIG.
1
. That is, in on a silicon platform substrate in which the optical waveguide
3
A and silicon substrate
1
are formed integrally, entry/exit end faces
3
b
to
3
d
are formed in the optical waveguide
3
A. The photo-receiving element
6
is fixed in place opposing the end face
3
b
on the silicon substrate
1
, by soldering or other means, and the light emitting element
5
is fixed in place on the silicon substrate
1
opposing the end face
3
d
, distant from the other end face, by soldering or other means. The module is designed such that an optical fiber can be connected, by means of an optical connector, to the end face
3
c.
In this optical waveguide transmitter-receiver module for ATM-PON systems, the light emitting element
5
and photo-receiving element
6
operate simultaneously. Consequently, resistance to crosstalk between optical transmission and reception signals is required. For this reason, the light emitting element
5
and photo-receiving element
6
are mounted on the silicon substrate as far apart as possible, and by this means, the adverse effects of electrical crosstalk induced by electromagnetic coupling via the silicon substrate between the light emitting element
5
and photo-receiving element
6
are reduced.
FIG. 3
is a perspective view of a conventional optical waveguide transmitter-receiver module for &pgr;-PON systems, with hybrid-integration of silicon substrate and PLC substrate respectively.
This optical waveguide transmitter-receiver module for &pgr;-PON systems has a silicon substrate
7
with flat surface; on the flat surface of this silicon substrate
7
is formed by etching a V-shaped etched groove (hereafter “V groove”)
8
, for aligned mounting of an optical fiber. An light emitting element
5
and photo-receiving element
6
are fixed in place on the silicon substrate by soldering or other means. A PLC substrate
9
, manufactured in advance, is fixed in place by resin, soldering or other means on the silicon substrate
7
, opposing the light emitting element
5
, photo-receiving element
6
, and V groove
8
. The PLC substrate
9
is formed by layered deposition of an optical circuit, to serve as the optical waveguide
3
B, on parent-material or matrix substrate, primarily silicon, quartz, or a polyimide. The optical waveguide
3
B is provided with entry/exit end faces
3
a
to
3
c
opposing the light emitting element
5
, photo-receiving element
6
, and V groove
8
.
In this optical waveguide transmitter-receiver module for &pgr;-PON systems, an optical fiber is inserted into the V groove
8
, and is bonded using a resin. For example, light emitted from the light emitting element
5
is incident on the end face
3
a
of the optical waveguide
3
B. The incident light passes through the branch part
3
e
, is emitted from the end face
3
c
, and is sent to the optical fiber in the V groove
8
. On the other hand, light sent from the optical fiber is incident on the end face
3
c
of the optical waveguide
3
B. The incident light passes through the branch part
3
e
, and is emitted from the end face
3
b
. The emitted light is received by the photo-receiving element
6
, and is converted into an electrical signal and output.
However, the conventional optical waveguide transmitter-receiver modules of
FIGS. 1
to
3
have the following problems (1) to (3).
(1) Case of the Optical Waveguide Transmitter-receiver Module Structure of FIG.
1
and
FIG. 2
An optical waveguide transmitter-receiver module such as that of FIG.
1
and
FIG. 2
adopts a silicon platform structure, in which the optical waveguide
3
,
3
A and silicon substrate
1
are integrated. That is, numerous optical waveguide transmi
Ngo Hung N.
Oki Electric Industry Co. Ltd.
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