Optoelectronic interconnect module

Details Optoelectronic interconnect module Optoelectronic interconnect module

2000-08-31

2002-09-24

Healy, Brian (Department: 2874)

Optical waveguides

With disengagable mechanical connector

Optical fiber to a nonfiber optical device connector

C385S092000, C385S088000, C385S031000, C385S033000

Reexamination Certificate

active

06454470

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates generally to optoelectronic interconnect modules for fiber optic communications. The present invention relates more specifically to an optoelectronic interconnect module enabling an optical transmitting or receiving semiconductor die to be mounted to a substrate with an optical axis perpendicular to an optical ferrule mounted to the optoelectronic interconnect module.
BACKGROUND OF THE INVENTION
Ultrafast optoelectronic transmitters are utilized in data communications systems wherein optical beams are modulated with electronic binary data pulses. The electronic pulses are conveyed by means of metallic conductors to a light-emitting semiconductor device, the modulated output of which may be transmitted over optical media (i.e., fiber optic cables).
Optoelectronic interconnect modules or optical subassemblies may be configured for direct mounting to a circuit substrate or a printed circuit board within the host system. In this arrangement, contact pins extend from the module and are typically soldered directly to contact points on the printed circuit board. The module is usually mounted near the edge of the printed circuit board such that the optical end of the module will protrude through a slot in an adjacent metal faceplate that may be mounted to the metal chassis of the host system.
A transceiver module includes provisions for connecting the module to an optical transfer medium such as a fiber optic cable. A typical arrangement, common to 1×9 modules, is to provide a transceiver module having an SC-duplex fiber optic connector receptacle integrally formed at the optical end of the module. The SC-duplex receptacle is configured to receive an SC-duplex connector in order to couple a pair of optical fibers to the optoelectronic interconnect module. A first optical fiber carries optical signals transmitted by the module, while a second optical fiber carries optical signals to be received by the module.
Ultrafast optoelectronic transceivers are capable of transmitting serial bit streams at rates above 10 Gbps. At these high data rates, electronic components and circuitry within the module are prone to generate undesired emissions and create electromagnetic interference with the surrounding equipment. Therefore, care must be taken to prevent spurious emissions from escaping from the module housing and disrupting the operation of nearby devices. Furthermore, electrical connections should be planar or straight to minimize signal distortion.
With reference to
FIG. 1
, a first embodiment of a prior art optoelectronic interconnect module is presented. The optoelectronic transceiver module
10
is inserted within the host chassis
12
. The module
10
includes a metallic or metallized connector clip having a first prong
14
and a second prong
15
for receiving and retaining a fiber optic connector. Aligned concentrically within the connector clip
14
,
15
is an optical subassembly. The optical subassembly includes an optical housing
16
, optical lens
24
, an annular mounting surface
32
, an alignment ring
34
, and an optoelectronic package
26
. The external end of the optical housing
16
defines a ferrule bore
18
configured to receive a fiber optic connector ferrule
20
which aligns the optical fiber
22
carried within the ferrule
20
with the optoelectronic device contained within the optoelectronic package
26
.
The optoelectonic package
26
is externally comprised of a metal cover
28
, an optical window
29
, and a base
30
. The base
30
and cover
28
are both formed of metal and are joined by a conductive interface allowing the optoelectronic package
26
to be maintained at a controlled electrical potential. An insulating substrate
36
is provided within the optical package on the upper surface of the base. An optoelectronic and electronic semiconductor die
38
is mounted to the insulating substrate
36
.
A plurality of signal pins extend through the base
30
and are wire-bonded to the optoelectronic and electronic semiconductor die
38
, which is mounted to the insulating substrate
36
. The signal pins
40
,
42
,
44
provide signal, voltage, ground to the optoelectronic and electronic semiconductor die
38
contained within the optoelectronic package
26
. The signal and voltage pins
40
,
42
are insulated from the base
30
by glass sleeves
46
disposed between the pins and the base. The ground pin
44
is connected to the base
30
by a weld joint
48
.
With reference to
FIG. 2
, a second embodiment of a prior art optoelectronic interconnect module
50
is presented. An optoelectronic semiconductor die
52
is bonded parallel to the end surface
70
of an optical fiber
54
within an optical ferrule
56
. The optoelectronic interconnect module housing
56
is constructed of an insulator and secured to a ceramic substrate
58
. Electronic components
60
that interface with the optoelectronic interconnect module
50
are also attached to the ceramic substrate
58
. Interconnect wires
62
provide an electrical connection between the electronic components
60
and the optoelectronic semiconductor die substrate
52
. If the optoelectronic interconnect module
50
is functioning as a transmitter, optical radiation
66
emitted by the semiconductor die
52
passes through an optical lens or ball lens
68
in order to be properly focused on the end
70
of the optical filament or fiber
54
. Similarly, if the optoelectronic interconnect module
50
is functioning as a receiver, optical radiation emitted from the end
70
of the optical fiber
54
passes through the ball lens
68
in order to be properly focused upon the semiconductor die
52
.
As can be seen in the second embodiment of the prior art concept shown in
FIG. 2
, the semiconductor die
52
is mounted axially in-line to the ferrule
56
and perpendicular to the substrate
58
, necessitating the connecting wires
62
to be bent about an angle
72
in order to connect with the electronic components
60
. The resulting bend
72
in the connecting wires
62
produces undesired signal distortion. Furthermore, the bend
72
in the connecting wires
62
increases production costs and decreases reliability of the optoelectronic interconnect module
50
.
The bend in connecting wires, which is basic to the electrical interconnection of both the referenced prior arts embodiments shown in
FIGS. 1 and 2
, poses basic limitations for ultra-fast optoelectronic transceiver performance. As compared to a planar or straight electrical interconnect counterpart, the bent interconnection:
increases production cost
decreases reliability
increases signal distortion
The cause of the signal distortion is explained in the following manner:
As the rate of data transmission increases, the connecting wires
62
providing electronic interconnection between the semiconductor die
52
and the electronic components
60
on the substrate
58
to which the module housing
56
is attached become a significant portion of signaling wavelength. In this operating regime, the connecting wires
62
behave as transmission lines with some impedance (Z).
With reference to
FIG. 3
, a schematic representation of the electronic interconnect between the semiconductor die contained within the optoelectronic housing and the electronic components is presented. As the interconnect impedance (Z) deviates from the system impedance (Z), frequency-dependent signal reflections will occur at the impedance mismatch, causing signal distortion. This signal distortion is the primary physical shortcoming in prior art designs that the present invention corrects by providing a planar interconnect that establishes an electronic connection of controlled impedance.
Accordingly, there is a need for an optoelectronic interconnect module that provides planar electronic interconnections and enables optical semiconductor die to be mounted in the same geometric plane as ancillary high speed electronic components within the transceiver assembly.
OBJECTS AND SUMMARY OF THE INVENTION
The objective of the pres

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