Optical waveguides – With optical coupler – Particular coupling structure
Reexamination Certificate
1999-10-25
2003-03-18
Bovernick, Rodney (Department: 2874)
Optical waveguides
With optical coupler
Particular coupling structure
C385S039000, C385S014000
Reexamination Certificate
active
06535670
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an optical transmitter and receiver module, and particular to an integrated optical transmitter/receiver module.
2. Description of the Related Art
Recently, image information communications have been increasingly more common and attempts to adopt optical cables for communications have been made. Among these attempts, the access system optical communication adopts light waves of a wavelength band centered around 1.3 &mgr;m for bidirectional communications between a plurality of subscribers and transmitter stations and at the same time, light waves of a wavelength band centered around 1.55 &mgr;m for distributing image information from a transmitter station to the subscribers. In this type of system, it is necessary to install a WDM (Wavelength Division Multiplexing) optical transmitter and receiver module on the subscribers side of the system.
In the optical transmitter and receiver module, a type of module that employs a dielectric multilayer filter, that is, a reflective wavelength de-multiplexer, has received attention since the module realizes isolation over a broad bandwidth (Japanese patent application kokai 8-190026). As shown in
FIG. 1
, in a prior art optical transmitter and receiver module, single mode wave guides
2
,
3
, and
2
′ each having a core contained in a cladding
12
made of quartz-based glass are formed on a silicon substrate
11
. Near a position of intersection of wave guides
2
and
3
, there is disposed a groove
4
formed with a dicing saw and a dielectric multilayer filter
5
is disposed therein. The optical axis of the wave guide
2
′ formed opposite to the wave guides
2
and
3
of the dielectric multilayer filter
5
is in alignment with the optical axis of the wave guide
2
.
In a planar light-wave circuit
30
, an input/output single mode optical fiber
10
A and an output single mode optical fiber
10
B are fixedly inserted into a glass block
9
. The glass block
9
is fixedly bonded to the end face of the circuit so that the optical axes of the input/output and output single mode optical fibers
10
A and
10
B are in alignment with the optical axes of the wave guides
2
and
3
respectively. Wavelength-multiplexed beams of light of wavelength bands centered around 1.3 &mgr;m and 1.55 &mgr;m are launched from the input/output port into the wave guide
2
. The light beam of a wavelength band centered around 1.55 &mgr;m is reflected at the dielectric multilayer filter
5
to be guided into the wave guide
3
and then is coupled into the single mode optical fiber
10
B at the end of the wave guide to be outputted. On the other hand, the light beam of a wavelength band centered around 1.3 &mgr;m from the wave guide
2
passes through the dielectric multilayer filter
5
, i.e., the reflective wavelength multiplexer/de-multiplexer, and enters the wave guide
2
′. The wave guide
2
′ is divided into two at a Y branch
6
in which one of branching wave guide is connected to a laser diode
7
and the other is a photo-diode
8
. The laser diode
7
is used for transmitting signals generated from one receiver of the subscribers to the input/output single mode optical fiber
10
A, whereas the photo-diode
8
is used for converting the received optical signals into electric signals. Beams of light of a wavelength band centered around 1.55 &mgr;m are used, for example, for distributing multi-channel video signals from a transmitter station to the subscribers, while beams of light of a wavelength band centered around 1.3 &mgr;m are used in bidirectional communications for transmitting various kinds of data signals.
In the foregoing, there are projections and depressions on the side face of a groove
4
dug and formed with a dicing saw. Accordingly, it is difficult to grind the groove side faces. Moreover, a dielectric multilayer filter
5
is formed by alternately depositing plural layers of SiO
2
and TiO
2
on a polyimide film of a predetermined thickness so that the dielectric multilayer filter
5
transmits light waves of a wavelength band centered around 1.3 &mgr;m and reflects a wavelength band centered around 1.55 &mgr;m. In addition, the film of this dielectric multilayer filter is inserted into the groove and fixed with a silicone adhesive
13
and is subject to deterioration with age. Furthermore, there is a problem in that the projections and depressions of the side face of the groove, the adhesive agent, and the plastic film cause the beams of light passing therethrough a great deal of loss in the reflection and transmission.
OBJECT AND SUMMARY OF THE INVENTION
Accordingly, the present invention has been made in view of the problem mentioned above, and its object is to provide an optical transmitter and receiver module, with less optical loss, which can be manufactured easily, and to provide the manufacturing method therefor.
The optical transmitter and receiver module according to the present invention for de-multiplexing a multi-wavelength optical signal into at least an optical signal of one wavelength band, and for receiving and transmitting the optical signal, said optical transmitter and receiver module comprising
input/output and output wave guides,
a transmit/receive wave guide,
a first substrate made of a cleavable crystal, having a cleavage plane, for supporting the input/output and output wave guides which intersect each other at a portion on the cleavage plane from which the input/output and output wave guides extend at an equal angle with respect to a normal line on said cleavage plane;
an interference filter in contact with said cleavage plane on the portion of intersection of the input/output and output wave guides of said first substrate; and
a second substrate made of the cleavable crystal having another cleavage plane in contact with said interference filter, for supporting a transmit/receive wave guide having receiver and transmitter wave guides which extend from a vicinity of said portion of intersection and are separated from each other.
In accordance with an aspect of the optical transmitter and receiver module of the invention, the first substrate has a second cleavage plane opposite to the cleavage plane having the portion of intersection on which the input/output and output wave guides terminate.
In accordance with another aspect of the optical transmitter and receiver module of the invention, the second substrate has another second cleavage plane opposite to the cleavage plane in contact with said interference filter on which the receiver and transmitter wave guides of the transmit/receive wave guide terminate.
In accordance with a further aspect of the optical transmitter and receiver module of the invention, the first and second substrate are made of InP, and the input/output and output wave guides and the transmit/receive wave guide are made of InGaAsP.
In accordance with a still further aspect of the optical transmitter and receiver module of the invention, the first and second substrate are made of GaAs, and the input/output and output wave guides and the transmit/receive wave guide are made of AlGaAs.
In accordance with another aspect of the optical transmitter and receiver module of the invention, the input/output and output wave guides and the transmit/receive wave guide are a channel-type three-dimensional wave guide.
In accordance with a further aspect of the optical transmitter and receiver module of the invention, the interference filter comprises a dielectric multilayer filter having a configuration for transmitting an optical signal of a shorter wavelength, and for reflecting an optical signal of a longer wavelength in the multi-wavelength optical signals.
In accordance with a still further aspect of the optical transmitter and receiver module of the invention, the optical transmitter and receiver module further comprises a photodetector and a light emitting device coupled to the receiver and transmitter wave guides of the transmit/receive wave guide respectively.
In accordance with another
Chen Nong
Chikuma Kiyofumi
Takei Kiyoshi
Watanabe Yoshiaki
Bovernick Rodney
Morgan & Lewis & Bockius, LLP
Pioneer Corporation
Stahl Mike
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