Optical waveguides – Integrated optical circuit
Reexamination Certificate
1999-09-23
2001-04-17
Sikder, Mohammad (Department: 2872)
Optical waveguides
Integrated optical circuit
C385S076000, C385S083000, C359S199200, C359S199200
Reexamination Certificate
active
06219470
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention generally relates to a wavelength division multiplexing transmitter and receiver module, and particularly relates to a wavelength division multiplexing transmitter and receiver module utilizing an etched silicon substrate as the mounting platform for the optical components and optoelectronic devices and a microstructure formed in the silicon substrate as the building base for the multiplexer and/or the demultiplexer.
In order to provide high bandwidth communications to the subscriber, some sophisticated system configurations based on full fiber-optic access network such as fiber-to-the-home (FTTH) or fiber-to-the-desktop (FTTD) are required. The technology for such systems exists, but it can not proliferate unless costs are reduced substantially, especially the costs of the opto-electronic network unit (ONU) working as a wavelength division multiplexing transmitter and receiver module. To make FTTH or FTTD economically feasible, several wavelength division multiplexing transmitter and receiver modules suitable for high-volume, low-cost manufacturing have been developed.
One such module, as shown in
FIG. 1
, comprises a sealed TO can transmitter
102
and a hermetically sealed TO can receiver
103
that are mounted in an orthogonal fashion in a common hollow housing
101
to effect the module. An optical fiber
108
is inserted in the housing through a connector
107
. The optical fiber transmits light to and from the module via a spherical lens
106
. An optical beamsplitter
105
supported by a spacer tube
104
can be wavelength dependent or a proportional splitter that deflects light in a defined intensity to the receiver or the detector. The wavelength selectivity requirement of the detector and the transmitter or the emitter is then effected by selective wavelength filtering prior to the light's impinging on the detector. The various subassemblies are then adjusted for optical alignment and finally fixed in final position.
The drawback to this configuration is that the autonomous emitter and detector are aligned in the common housing either iteratively or successively with the various optical elements of the system to optimize the input and output performance. This approach is clearly a complicated and labor intensive approach, which accordingly increases the cost of the devices. Furthermore, in the preferred embodiment, the lens element for the light emitter is within the encapsulation, and the optical alignment of this due to the close proximity of the lens to the emitter is rather difficult, and thus a labor intensive effort that serves to further increase the cost of manufacture.
Another wavelength division multiplexing transmitter and receiver module, as shown in
FIG. 2
, consists of three major parts: an optical block
201
, an optical network unit chip
206
, and an electronic block
210
. On the optical block
201
side, an optical fiber
203
held in a V-groove of a silicon wafer
202
and coming from the subscriber line terminal is coupled to the planar microlens
205
where wavelengths of 1.3 &mgr;m (digital voice signal) and 1.55 &mgr;m (analog video signal) are converted into collimated optical beams. The optical network unit chip
206
, fabricated by stacked planar optical technique, is composed of stacked glass slices coated by dielectric multilayered filters such as wavelength division multiplexing splitting filters
207
, half-mirrors
209
and mirrors
208
a
,
208
b
. This unit is then sandwiched by planar microlens array blocks. At the optical network unit chip
206
, wavelengths of 1.3 &mgr;m and 1.55 &mgr;m are split by the dielectric multilayered wavelength division multiplexing filter
207
in such way that 1.3 &mgr;m wavelength is transmitted straight while the 1.55 &mgr;m one is reflected. The wavelength of 1.3 &mgr;m is reflected by the half-mirror
209
and the mirror
208
b
, focused by one of the microlenses of the planar microlens array, located next to the electronic block
210
, and then detected by a 1.3 &mgr;m photodetector
212
. The wavelength of 1.55 &mgr;m is reflected by the mirror
208
a
, focused by another microlens of the planar microlens array and detected by a 1.55 &mgr;m photodetector
213
. For 1.3 &mgr;m transmission, a light optical beam coming from the 1.3 &mgr;m laser diode
211
, located at the electronic block
210
, is coupled with a microlens of the planar microlens array converting it into a collimated optical beam. Then, it enters the optical network unit chip
206
, passing straight through the half-mirror
209
and the wavelength division multiplexing filter
207
, and focused onto the optical fiber
203
located at the optical block
201
at the planar microlens array. Coupling between the planar microlens array
205
and the optical fiber
203
is realized by a put-in micro-connector scheme
204
. The dielectric multilayered wavelength division multiplexing filters
207
, half-mirrors
209
and mirrors
208
a
,
208
b
are fabricated by electron optical beam evaporation method on the glass substrate.
In this configuration the optical network unit and the planar microlens arrays block are not integrated in a single substrate. Active alignment and fixation for connecting the optical network unit and the planar microlens arrays block are still required. The space between the two adjacent optical beams coming out of the optical network unit is small since the optical network unit is formed by the thin-film deposition technology. This would make the interface of the optical network unit with the optoelectronic devices very complicated because the optoelectronic devices have not been shrunk accordingly to match the size of the optical network unit.
SUMMARY OF THE INVENTION
A purpose of the present invention is to provide a wavelength division multiplexing transmitter and receiver module utilizing a micromachined silicon substrate as the mounting platform for its needed components and devices and a microstructure integrally created in the silicon substrate as the building base for the multiplexer and/or the demultiplexer.
Another purpose of the present invention is to provide a wavelength division multiplexing transmitter and receiver module allowing its optical components including microlenses, filters, half-mirror, and anti-reflectors to be fabricated in a manner similar to semiconductor devices.
Still another purpose of the present invention is to provide a wavelength division multiplexing transmitter and receiver module assembled by using technologies developed for multi-chip modules (MCM) packaging.
Still another purpose of the present invention is to provide a wavelength division multiplexing transmitter and receiver module allowing an optical fiber incorporated into the module in a passive alignment manner.
Still another purpose of the present invention is to provide a wavelength division multiplexing transmitter and receiver module having a transmitter pre-mounted on a V-submount so that it can be incorporated into the module in a passive alignment manner.
Still another purpose of the present invention is to provide a wavelength division multiplexing transmitter and receiver module having microlenses each disposed on a side surface of a V-support so that they are incorporated into the module in a passive alignment manner.
REFERENCES:
patent: 5757999 (1998-05-01), Tabuchi et al.
patent: 5859943 (1999-01-01), Asakura et al.
patent: 6085000 (2000-07-01), Tanaka et al.
Johnsonbaugh Bruce H.
Sikder Mohammad
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