Parallel optical transceiver module that utilizes a folded flex circuit that reduces the module footprint and improves heat dissipation

A parallel optical transceiver module is provided that uses a folded flex circuit arrangement that reduces the footprint of the transceiver module while also providing the module with improved heat dissipation characteristics. In addition, the manner in which components are mounted on the flex circuit facilitates assembly of the module, reducing the overall cost of the module while improving manufacturing yield.

TECHNICAL FIELD OF THE INVENTION

The invention relates to parallel optical transceiver modules. More particularly, the invention relates to a parallel optical transceiver module that uses a folded flex circuit to reduce the spatial footprint of the module while also providing improved heat dissipation characteristics.

BACKGROUND OF THE INVENTION

FIG. 1illustrates a block diagram of a parallel optical transceiver module2currently used in optical communications, which has multiple transmit and multiple receive channels. The transceiver module2includes a transmitter portion3a receiver portion4. The transmitter and receiver portions3and4are controlled by a transceiver controller6. The transmitter portion3comprises components for transmitting data in the form of amplitude modulated optical signals over multiple fibers (not shown). The transmitter portion includes a laser driver11and a plurality of laser diodes12. The laser driver11outputs electrical signals to the laser diodes12to modulate them. When the laser diodes12are modulated, they output optical signals that have power levels corresponding to logic 1s and logic 0s. An optics system (not shown) of the transceiver module2focuses the optical signals produced by the laser diodes12into the ends of respective transmit optical fibers (not shown) held within a connector (not shown) that mates with the transceiver module.

Typically, a plurality of monitor photodiodes14monitor the output power levels of the respective laser diodes12and produce respective electrical feedback signals that are fed back to the transceiver controller6, which processes them to obtain respective average output power levels for the respective laser diodes12. The controller6outputs controls signals to the laser driver11that cause it to adjust the bias current signals output to the respective laser diodes12such that the average output power levels of the laser diodes are maintained at relatively constant levels.

The receiver portion4includes a plurality of receive photodiodes21that receive incoming optical signals output from the ends of respective receive optical fibers (not shown) held in the connector. The optics system (not shown) of the transceiver module2focuses the light output from the ends of the receive optical fibers onto the respective receive photodiodes21. The receive photodiodes21convert the incoming optical signals into electrical analog signals. The transceiver controller6and/or other circuitry (not shown) of the transceiver module2processes the electrical signals to recover the data represented by the signals.

The laser driver11is typically a separate integrated circuit (IC). The laser diodes12are typically also contained in a separate IC. The monitor photodiodes14are typically also contained in a separate IC. The transceiver controller6is also typically a separate IC. The receiver photodiodes21are also typically contained in a separate IC. In addition to these ICs, the transceiver module2typically also includes a receiver IC that processes electrical data signals corresponding to the electrical signals produced by the receiver photodiodes21. These ICs and other components, such as resistors, capacitors and optical elements (e.g., lenses) are typically mounted on some type of circuit board, such as a printed circuit board (PCB) having a generally rigid substrate on which conductive traces are printed or a flexible circuit substrate on which conductive traces are printed or etched. Flexible circuit substrates used for this purpose are typically referred to as flex circuits. Some parallel optical transceiver modules use both a PCB on which some of the aforementioned components are mounted and a flex circuit on which others of the aforementioned components are mounted.

Typically, the PCB or flex circuit includes, or is otherwise in contact with, a heat spreader device, such as a layer of metallic material or a leadframe, for example. The purpose of the heat spreader device is to dissipate heat generated by the electrical components by spreading the heat out away from the components that can be adversely affected by heat. The heat spreader device is typically a generally planar device that spreads heat laterally in directions that are generally coplanar with the plane of the heat spreader device. The heat spreading function is particularly important with respect to the laser diode IC because the performance of a laser diode can easily degrade as its temperature increases. The laser diode driver IC, which is typically placed relatively close to the laser diode IC in order to avoid long lead lengths, generates a large amount of heat. One of the primary functions of the heat spreader device is to move the heat generated by the driver IC away from the laser diode IC so that the heat does not adversely affect the performance of the laser diodes contained in the laser diode IC.

In addition to heat dissipation considerations, there are other considerations that are typically taken into account when designing parallel optical transceiver modules, such as size and inductive coupling, for example. It is generally a design goal for the transceiver module to be small in size, or to have a small “footprint”. It is also typically a design goal to have relatively short lead lengths in order to prevent or minimize inductive coupling between adjacent electrical conductors (e.g., wire bonds), which can lead to noise and performance degradation. Placing the laser diode driver IC close to the laser diode IC helps to reduce the footprint of the module and, at the same time, to enable the lengths of the wire bonds that connect the pads of the ICs to be kept relatively short. Keeping these conductor lengths short helps to prevent or minimize inductive coupling between adjacent conductors. However, placing these ICs in close proximity to one another makes it more difficult to isolate the laser diode IC from the heat generated by the laser diode driver IC. Thus, there are tradeoffs that require some balancing between these and other design goals.

A need exists for a parallel optical transceiver module that has a relatively small footprint, is efficient in terms of space consumption, has good heat dissipation characteristics, and that can be manufactured at relatively low cost with relatively high yield.

SUMMARY OF THE INVENTION

The invention is directed to a parallel optical transceiver module that uses a folded flex circuit and methods for pre-assembling and assembling a parallel optical transceiver module. In accordance with an embodiment, the parallel optical transceiver module has a folded flex circuit having at least upper and lower surfaces and having at least first, second and third flex circuit portions. The flex circuit has a flexible substrate of dielectrically insulating material and a plurality of electrical conductors disposed in or on the substrate. The first and third flex circuit portions extend generally in respective planes that are generally parallel to one another such that the upper surface of the flex circuit in the first flex circuit portion is generally parallel to the upper surface of the flex circuit in the third flex circuit portion. At least one optical/electrical device is mounted on the first flex circuit portion on the upper surface of the flex circuit. The optical/electrical device has one or more electrical contacts that are electrically coupled to one or more of the electrical conductors of the flex circuit. At least one electrical connector is mounted on the third flex circuit portion on the upper surface of the flex circuit. The electrical connector has one or more electrical contacts that are electrically coupled to one or more of the electrical conductors of the flex circuit such that one or more of the electrical contacts of the electrical connector are electrically coupled to one or more electrical contacts of the optical/electrical device.

In accordance with another embodiment, the parallel optical transceiver module has a folded flex circuit having at least upper and lower surfaces and having at least first, second, third, fourth, and fifth flex circuit portions. The folded flex circuit has a flexible substrate of dielectrically insulating material and a plurality of electrical conductors disposed in or on the substrate. The first and fifth flex circuit portions extend generally in respective planes that are generally co-planar to one another and generally parallel to a plane in which the third flex circuit portion extends such that the upper surface of the flex circuit in the first and fifth flex circuit portions are generally co-planar to one another and generally parallel to the upper surface of the flex circuit in the third flex circuit portion. At least a first optical/electrical device is mounted on the first flex circuit portion on the upper surface of the flex circuit. The first optical/electrical device has one or more electrical contacts that are electrically coupled to one or more of the electrical conductors of the flex circuit. At least a second optical/electrical device is mounted on the fifth flex circuit portion on the upper surface of the flex circuit. The second optical/electrical device has one or more electrical contacts that are electrically coupled to one or more of the electrical conductors of the flex circuit. At least one electrical connector is mounted on the third flex circuit portion on the upper surface of the flex circuit. The electrical connector has one or more electrical contacts that are electrically coupled to one or more of the electrical conductors of the flex circuit such that electrical contacts of the electrical connector are electrically coupled to electrical contacts of the first and second optical/electrical devices.

In accordance with one embodiment, a method for pre-assembling a parallel optical transceiver module is provided. The method comprises providing a generally planar flex circuit having at least upper and lower surfaces and having at least first, second and third flex circuit portions, mounting at least one optical/electrical device on the first flex circuit portion on the upper surface of the flex circuit, mounting at least one electrical connector on the third flex circuit portion on the upper surface of the flex circuit, and folding the flex circuit such that the upper surface of the flex circuit in the first flex circuit portion is generally parallel to the upper surface of the flex circuit in the third flex circuit portion.

In accordance with another embodiment, a method is provided for assembling a parallel optical transceiver module that includes a folded flex circuit. The method includes providing a folded flex circuit having at least upper and lower surfaces and having at least first, second and third flex circuit portions. The flex circuit has a flexible substrate of dielectrically insulating material and a plurality of electrical conductors disposed in or on the substrate. The first and third flex circuit portions extend generally in respective planes that are generally parallel to one another such that the upper surface of the flex circuit in the first flex circuit portion is generally parallel to the upper surface of the flex circuit in the third flex circuit portion. The method includes mounting at least one optical/electrical device on the first flex circuit portion on the upper surface of the flex circuit and mounting at least one electrical connector on the third flex circuit portion on the upper surface of the flex circuit.

These and other features and advantages of the invention will become apparent from the following description, drawings and claims.

DETAILED DESCRIPTION OF AN ILLUSTRATIVE EMBODIMENT

In accordance with the invention, a parallel optical transceiver module is provided that uses a folded flex circuit arrangement that reduces the footprint of the transceiver module while also providing the module with improved heat dissipation characteristics. In addition, the manner in which components are mounted on the flex circuit facilitates manufacturing of the module, thereby reducing the overall cost of the module while improving manufacturing yield.

FIG. 2illustrates a side view of the parallel optical transceiver module100of the invention in accordance with an illustrative embodiment. The module100includes a flex circuit110having an upper surface110A and a lower surface110B. The flex circuit110has a first fold110C and a second fold110D formed therein. The folds110C and110D subdivide the flex circuit110into a first portion110E, a second portion110F and a third portion110G. Each of the first, second and third portions110E,110F and110G is generally planar in geometry and extends in a respective plane. For example, assuming the module100is oriented in a reference frame that is defined by an X, Y, Z Cartesian coordinate system, the first and third portions110E and110G extend in respective X-Y planes that pass through the Z-axis at different respective Z coordinates. The second portion110F extends in a Y-Z plane that passes through the X-axis at a particular X coordinate. Thus, the respective X-Y planes in which the first and third portions110E and110G extend are parallel to each other and are orthogonal to the Y-Z plane in which the second portion110F extends. It should be noted, however, that the flex circuit110may have other orientations and that the portions110E-110G need not be parallel or orthogonal to each other.

The transceiver module100includes one or more optical-to-electrical or electrical-to-optical devices, such as a laser diode IC (not shown) and/or a receive photodiode IC (not shown), for example, which are mounted on the upper surface110A of the first portion110E of the flex circuit110. These components are represented by block115inFIG. 2. Typically, both a laser diode IC and a receive photodiode IC are mounted on the upper surface110A of the first portion110E. Electrical devices preferably are also mounted on the upper surface110A of the first portion110E of the flex circuit110. The term “optical/electrical device” will be used herein to refer to electrical-to-optical devices and to optical-to-electrical devices. Block117inFIG. 2represents one or more other devices mounted on the upper surface110A of the flex circuit110on the first portion110E. The other devices represented by block117may include, for example, a laser diode driver IC and/or a receiver IC and/or a transceiver controller IC.

An electrical connector140is mounted on the upper surface110A of the third portion110G of the flex circuit110. The electrical connector140may be, for example, a ball grid array (BGA), a pin grid array (PGA), or a land grid array (LGA). The electrical connector140provides an electrical interface for electrically interconnecting the module100with other electrical circuits, such as a PCB or another IC, for example. The flex circuit110is typically made of a dielectrically insulating material, such as, for example, polyimide (PI), polyester (PET), or polyethylene napthalate (PEN), and has a pattern of electrical conductors (not shown) disposed in or on it. At least some of the electrical conductors of the flex circuit110have first ends that are electrically coupled to electrical contacts (not shown) of the devices115and117and second ends that are electrically coupled to electrical contacts (not shown) of the electrical connector140.

A stiffener device125, which is typically made up of a substantially rigid material, such as aluminum, for example, is provided in the module100. The stiffener125typically comprises first and second stiffener portions125A and125B, respectively, which are separate from one another, although a single-part stiffener may instead be used for this purpose. First ends125C and125D of the stiffener portions125A and125B, respectively, pass through slots110K and110L, respectively, formed in the flex circuit110and come into contact with an inner wall of the module housing130. Second ends125E and125F of the stiffener portions125A and125B, respectively, also come into contact with inner walls of the module housing130. The stiffener125provides mechanical stability to the flex circuit110to help maintain the first, second and third portions110E,110F and110G of the flex circuit110in their respective, generally planar positions.

The material that the stiffener125is made of preferably is thermally conductive. Heat generated by the components represented by blocks115and117is transferred from the flex circuit110into the stiffener portion125A and then is spread out laterally throughout the stiffener portion125A. The module housing130preferably is also made of a thermally conductive material, such as aluminum or copper, for example. Making the module housing130of a thermally conductive material ensures that at least some of the heat that is transferred into the stiffener125is subsequently transferred into the housing130via the mechanical coupling between the ends125C,125D,125E, and125F of the stiffener device125and the inner wall of the housing130.

Preferably, the module100includes an optics system holder160that is seated and secured to the upper surface110A of the third portion110E of the flex circuit110. The optics system holder160holds an optics system170, which is positioned below and in substantial alignment with an opening131formed in the housing130. The optics system170is designed to couple light between laser diodes (not shown) of the transmitter side of the module100and transmit optical fibers (not shown) and to couple light between photodiodes of the receiver side and receive optical fibers (not shown). The optics system170may include one or more lenses for focusing light generated by laser diodes into the ends of transmit fibers, one or more lenses for focusing light propagating out of the ends of receive fibers onto respective photodiodes, one or more optically diffractive elements for diffracting light, one or more optically reflective elements, one or more optically refractive elements, and/or one or more imaging elements. The invention is not limited to any particular design or configuration for the optical system170. Also, separate respective optics systems170may be provided for the transmit side and for the receive side of the transceiver module100.

It can be seen fromFIG. 2that the footprint of the module100, i.e., the area of the module100in the X and Y dimensions, is only about as large as the area of the electrical connector140in the X and Y dimensions. This small module footprint is made possible through the folded configuration of the flex circuit110and by mounting the components represented by blocks115,117on the first portion110E opposite the portion110G on which the electrical connector140is mounted. The small footprint of the module100is advantageous for several reasons, one being that it enables the module100to be used in a customer system that has high component density.

In such environments, it is very important for the module100to have very good heat dissipation characteristics. The module100includes a heat spreader device150for dissipating heat generated by components of the module100. The heat spreader device150is not limited to having any particular configuration or shape. The configuration of the heat spreader device shown inFIG. 2is one of many possible configurations for the heat spreader device150. The heat spreader device150is made of a thermally conductive material, such as copper or aluminum, for example. The heat spreader device150comprises a first heat spreader portion150A and a second heat spreader portion150B. The first heat spreader portion150A includes a base150C and a plurality of legs150D having proximal ends that are attached to or integrally formed with the base150C and having distal ends that are disposed a particular distance away from the base150C. The base150C is in contact with the stiffener portion125A so that most of the heat that is transferred into the stiffener portion125A is then transferred into base150C of the first heat spreader portion150A. The second heat spreader portion150B preferably is identical in shape to the first heat spreader portion150A. The second heat spreader portion150B includes a base150E and a plurality of legs150F having proximal ends that are attached to or integrally formed with the base150E and having distal ends that are disposed a particular distance away from the base150E. The base150E is in contact with the stiffener portion125B so that most of the heat that is transferred into the stiffener portion125B is then transferred into the base150E of the second heat spreader portion150B.

FIG. 3illustrates a side view of the heat spreader device150shown inFIG. 2in accordance with an illustrative or exemplary embodiment. The distal ends150G of the first heat spreader portion150A come into contact with the base150E of the second heat spreader portion150B. Likewise, the distal ends150H of the second heat spreader portion150B come into contact with the base150C of the first heat spreader portion150A. The proximal ends150I and150J of the outermost ones of the legs150D and150F, respectively, of the first and second heat spreader portions150A and150B, respectively, have small locking indentations150K formed in them. The distal ends150G and150H of the outermost ones of the legs150D and150F, respectively, of the first and second heat spreader portions150A and150B, respectively, have small locking protrusions150L formed in them. These locking indentations and protrusions150K and150L, respectively, form a self-locking mechanism that locks the heat spreader portions150A and150B together in the position depicted inFIGS. 2 and 3when the flex circuit110is folded. Specifically, respective ones of the indentations150K interlock with respective ones of the protrusions150L when the flex circuit110(FIG. 2) is folded inwards by approximately 180°. In this manner, the folded configuration of the flex circuit110is fixed and stabilized.

In between the legs150D and150F of the first and second heat spreader portions150A and150B, respectively, air gaps exist that allow air to flow between the heat spreader portions150A and150B. As heat spreads into the legs150D and150F of the heat spreader portions150A and150B, respectively, at least some of the heat is dissipated by the air flowing between the legs150D and150F. This heat dissipation system is very effective and allows the first and third portions110E (FIG. 2) and 110G(FIG. 2), respectively, of the flex circuit110(FIG. 2) to be in relatively close proximity to one another, which enables the module100(FIG. 2) to be very small in the Z dimension. Thus, the module100(FIG. 2) has a very small footprint in the X and Y dimensions and is very compact in height (i.e., the Z dimension). These features of the invention are highly desirable and are particularly advantageous for a parallel optical transceiver module that has multiple transmit and/or multiple receive channels and associated circuitry, which tend to generate a large amount of heat.

Preferably, the module100(FIG. 2) is secured within a housing130(FIG. 2), although the module100can be used without the housing. When the module100is housed in the housing130, the components represented by boxes115and117(FIG. 2) are completely contained within the housing130(FIG. 2). Containment of these components within the housing130(FIG. 2) reduces or eliminates problems with electrostatic discharge (ESD) and electromagnetic interference (EMI), which are problems often encountered in known optical transceiver modules. In addition, the housing130(FIG. 2) helps to prevent or reduce the existence of dust and other particles inside of the housing130. The existence of dust and other particles can degrade the performance of laser diodes and photodiodes. Thus, the housing130(FIG. 2) helps to ensure that the performance of these components115,117and of the transceiver module100will not be detrimentally affected by dust and other particles.

FIG. 4illustrates a side view of the module100shown inFIG. 2when the module100is in its pre-assembled form. The pre-assembled module200is essentially identical to the assembled module100shown inFIG. 2except that the pre-assembled module200does not include the housing130shown inFIG. 2and the flex circuit110is in its unfolded state. In accordance with the embodiment shown inFIG. 4, prior to the folding of the flex circuit110and assembling the module100, the flex circuit110is a generally planar substrate extending only in the X-Y plane. For purposes of discussion and demonstration, it is assumed that the flex circuit110has only a length (i.e., an extent in the X dimension) and width (i.e., an extent in the Y dimension). However, it will be understood by those of ordinary skill in the art that the flex circuit110, in its unfolded state, has some finite thickness (i.e., an extent in the Z dimension) when it is in its unfolded state, although the thickness is typically extremely small.

During a pre-assembly process, the pre-assembled module200is created as follows. The components represented by blocks115,117are mounted on the upper surface110A of the first portion110E of the flex circuit110. The optics system holder160is secured the upper surface110A of the first portion110E. The optics system170may be secured to the holder160at this time or at some later time. On the upper surface110A of the third portion110G of the flex circuit110, the electrical connector140is mounted. On the lower surface110B of the first portion110E of the flex circuit110, the first stiffener portion125A is mounted. The first heat spreader portion150A is secured to the first stiffener portion125A. On the lower surface110B of the third portion110G of the flex circuit110, the second stiffener portion125B is mounted. The second heat spreader portion150B is secured to the second stiffener portion125B.

After the pre-assembly process has been performed to obtain the pre-assembled module200shown inFIG. 4, an assembly process is performed during which the flex circuit110is folded inwards by about 180° until the locking mechanism comprising the indentations and protrusions150K and150L (FIG. 3), respectively, formed on the outermost ones of the legs150D and150F (FIG. 3), respectively, is locked, as described above with reference toFIG. 3. For ease of illustration, the indentations150K and protrusions150L are not shown inFIG. 4. After the flex circuit110has been folded, the flex circuit110has the shape shown in and described above with reference toFIG. 2. Subsequently, the folded flex circuit110having the components115,117,125,140,150,160, and170secured thereto is secured within the housing130(FIG. 2) to achieve the configuration of the module100shown inFIG. 2. The ease with which the module100shown inFIG. 2is assembled in this manner facilitates the overall manufacturing process and helps to improve manufacturing yield.

The pre-assembly and assembly processes may be combined into a single assembly process or they may be performed as completely separate processes. For example, one manufacturer may manufacture the pre-assembled module200shown inFIG. 4and then a different manufacturer or the customer may obtain the pre-assembled modules200and perform the assembly process described above to create the assembled module100shown inFIG. 2. Also, many other well known steps are typically performed during the pre-assembly and/or the assembly process, such as, for example, die attachment processes, wire bonding processes, optical and mechanical alignment steps, etc In the interest of brevity, these well known steps that are typically used during optical transceiver module manufacturing processes will not be described herein.

FIG. 5illustrates a side view of an optical communications module300in accordance with another illustrative embodiment in which two optical transceiver modules400and500utilize a single flex circuit310and a single electrical connector340. The flex circuit310shown inFIG. 5may be identical to the flex circuit110described above with reference toFIG. 2, except that the flex circuit310typically has a length (i.e., extent in the X dimension) that is greater than the length of the flex circuit110to enable additional components to be mounted on the flex circuit310. Like the flex circuit110(FIG. 2), the flex circuit310shown inFIG. 5has an upper surface310A and a lower surface310B. In accordance with this embodiment, the flex circuit310has a first fold310C, a second fold310D, a third fold310E, and a fourth fold310F formed in it. The folds310C,310D,310E, and310F subdivide the flex circuit310into a first portion310G, a second portion310H, a third portion310I, a fourth portion310J, and a fifth portion310K. Each of the first, second, third, fourth and fifth portions310G,310H,310I,310J, and310K, respectively, is generally planar in geometry and extends in a respective plane. For example, assuming the module300is oriented in a reference frame that is defined by an X, Y, Z Cartesian coordinate system, the first, third and fifth portions310G,310I and310K extend in respective X-Y planes that pass through the Z-axis at different respective Z coordinates. The second and fourth portions310H and310J, respectively, extend in a Y-Z plane that passes through the X-axis at a particular X coordinates. Thus, the respective X-Y planes in which the first, third and fifth portions310G,310I and310K, respectively, extend are parallel to each other and are orthogonal to the Y-Z plane in which the second portion and fourth portions310H and310J, respectively, extend.

The transceiver modules400and500each include one or more optical/electrical devices, such as a laser diode IC (not shown) and/or a receive photodiode IC (not shown), for example, which are mounted on the upper surface310A of the flex circuit310on the first portion310G and the fifth portion310K of the flex circuit310. Typically, both a laser diode IC and a receive photodiode IC are mounted on the upper surface310A of the flex circuit310on the first and fifth portions310G and310K, respectively. The blocks415and515each represent one or more optical/electrical devices. Blocks417and517each represent one or more other electrical devices that are mounted on the upper surface310A of the flex circuit310on the first and fifth portions310G and310K, respectively. The other devices represented by blocks417and517may include, for example, a laser diode driver IC and/or a receiver IC and/or a transceiver controller IC.

An electrical connector340is mounted on the upper surface310A of the flex circuit310on the third portion310I. The electrical connector340may be, for example, a BGA, a PGA, or a LGA. The electrical connector340provides an electrical interface for electrically interconnecting the optical communications module500with other electrical circuits, such as a PCB or another IC, for example. The flex circuit310is typically made of a dielectrically insulating material, such as, for example, PI, PET, or PEN, and has a pattern of electrical conductors (not shown) disposed in or on it. At least some of the electrical conductors of the flex circuit310have first ends that are electrically coupled to electrical contacts (not shown) of the devices represented by blocks415,417,515, and517and second ends that are electrically coupled to electrical contacts (not shown) of the electrical connector340.

The transceiver modules400and500include stiffener devices425and525, respectively. Each of the stiffener devices425and525is typically made up of a substantially rigid material, such as aluminum, for example. The stiffeners425and525each typically comprise first and second stiffener portions425A,425B and525A,525B, respectively, which are separate from one another, although a single-part stiffener device may instead be used for this purpose. The stiffener devices425and525may be identical to the stiffener device125described above with reference toFIG. 2. Therefore, in the interest of brevity, a detailed description of the stiffener devices425and525will not be provided herein.

The optical communications module300includes a housing330, which is essentially identical to the housing130described above with reference toFIG. 2. Preferably, the transceiver modules400and500include optics system holders460and560, respectively, that are seated and secured to the upper surface310A of the first and fifth portions310G and310K, respectively, of the flex circuit310. The optics system holders460and560hold optics systems470and570, respectively, which are positioned below and in substantial alignment with openings331A and331B, respectively, formed in the housing330. The holders460,560and the optics system470,570preferably are identical to the holder160and the optics system170, respectively, described above with reference toFIG. 2.

It can be seen fromFIG. 5that the footprint of the optical communications module300, i.e., the area of the module300in the X and Y dimensions, is only about as large as the area of the electrical connector340in the X and Y dimensions. This small module footprint is made possible through the folded configuration of the flex circuit310and by mounting the components represented by blocks415,417,515, and517on the first and fifth flex circuit portions310G and310K opposite the flex circuit portion310I on which the electrical connector340is mounted. The small footprint of the module300is advantageous for the same reasons as those described above with reference to the module100shown inFIG. 2.

The modules400and500include heat spreader devices450and550, respectively, for dissipating heat generated by components of the module400and500, respectively. The heat spreader devices450and550include first and second heat spreader portions450A,450B and550A,550B, respectively. The heat spreader devices450and550preferably are identical to the heat spreader device150described above with reference toFIGS. 2 and 3. Therefore, in the interest of brevity, a detailed description of the heat spreader devices450and550will not be provided herein.

The communications module300has many of the same advantages as those described above with reference to the module100shown inFIG. 2. As indicated above, the module300has a relatively small footprint. The module300is also compact in height (small in the Z dimension). The module300also has very good heat dissipation characteristics. The module300is also efficient in terms of parts in that the transceiver modules400and500utilize the same flex circuit310and the same electrical connector340. The module300may be pre-assembled and assembled in a similar manner to that in which the module100(FIG. 2) is pre-assembled and assembled, except that the flex circuit310of the module300has additional folds formed in it and an at least one additional optical/electrical device415and electrical device417mounted thereon. Therefore, a detailed description of the pre-assembly and assembly processes that are used to make the module300will not be provided herein.

It should be noted that the term “optical transceiver module” as that term is used herein, is intended to denote a module that only has parts for functioning as a transmitter, or that only has parts for functioning as a receiver, or has parts for functioning as both a transmitter and as a receiver. Thus, the transceiver module100shown inFIG. 1may include only transmit channel parts, only receive channel parts, or both transmit and receive channel parts. Likewise, each of the transceiver modules400and500shown inFIG. 5may include only transmit channel parts, only receive channel parts, or both transmit and receive channel parts. For example, module400may include only transmit channel parts while module500includes only receive channel parts, and vice versa. Alternatively, modules400and500may each include both transmit and receive channel parts. Similarly, the term “optical transceiver module”, as that term is used herein, denotes a module that includes a single optical transceiver module of the type shown inFIG. 2as well as a module that includes multiple optical transceiver modules, such as that shown inFIG. 5.

FIG. 6illustrates a flowchart that represents the method of the invention in accordance with an illustrative embodiment for assembling an optical transceiver module that utilizes a folded flex circuit. The method includes providing a folded flex circuit having an upper surface and a lower surface and having at least first, second and third flex circuit portions, wherein one or more optical/electrical devices are mounted on the upper surface on the first flex circuit portion and an electrical connector is mounted on the upper surface on the third flex circuit portion, as indicated by block601. As described above with reference toFIGS. 2-5, the transceiver module preferably includes stiffener and heat sink devices. As an additional, but optional, step, the transceiver module is secured within a housing such that the optical/electrical devices are contained within the housing, as indicated by block603.

FIG. 7illustrates a flowchart that represents the method of the invention in accordance with an illustrative embodiment for pre-assembling an optical transceiver module. As indicated by block701, a flex circuit is provided that has at least an upper surface and a lower surface and first, second and third flex circuit portions. One or more optical/electrical devices are mounted on the upper surface on the first portion of the flex circuit, as indicated by block703. An electrical connector is mounted on the upper surface of the flex circuit on the third flex circuit portion, as indicated by block705. As indicated above with reference toFIG. 4, subsequent to the pre-assembly process, the flex circuit is folded such that the first and third flex circuit portions extend generally in respective planes that are generally parallel to one another, as indicated by block707.

It should be noted that the second portion110F of the flex circuit110shown inFIG. 2and the second and fourth portions310H and310J of the flex circuit310shown inFIG. 5provide additional mounting areas on the flex circuits110and310, respectively. Other components or devices may be mounted in these additional areas on the upper and/or lower surfaces110A,110B and310A,310B of the flex circuits110and310, respectively. Also, additional components or devices not mentioned above may be mounted on the first and third portions110E and110G of flex circuit110(FIG. 2) and on the first, third and fifth portions310G,310I and310K of the flex circuit310(FIG. 5). As will be understood by persons of ordinary skill in the art, other modifications may also be made to the embodiments described herein.

It should be noted that the invention has been described with respect to a few illustrative embodiments for the purpose of describing the principles and concepts of the invention. The invention is not limited to these embodiments. For example, while the invention has been described with reference to using a particular heat spreader device configuration, the invention is not limited to this particular configuration. As will be understood by those skilled in the art in view of the description being provided herein, modifications may be made to the embodiments described herein while still achieving the goals of the invention, and all such modifications are within the scope of the invention.