Patent Application
20050276612
This technology relates to fiber-to-the-home applications. In particular, the technology concerns an opto-electronic module for use in fiber-to-the-home applications, among other applications
Fiber-to-the-home (FTTH) architecture involves fiber deployment to a customer's home and is a means for providing high-speed data, dependable voice service, and high-quality video. One issue in current FTTH designs is cost. Low cost systems are preferred and necessary for the ultimate implementation of FTTH architecture. The opto-electronic module is one component of the FTTH architecture that drives costs.
Construction of opto-electronic modules typically requires assembly techniques that provide alignment of waveguide components with other components in the module, all within the confines of a modular construction. Current constructions of opto-electronic modules require alignment of the components to positional tolerances within tenths of microns. This level of precision requires specialized techniques, such as laser welding or corrective optical elements. In addition, once aligned and secured, these assemblies must remain stable throughout the modules lifetime and during environmental stressing. For low cost packaging, this is difficult to accomplish.
In accordance with the teachings described herein, an opto-electronic module comprises a platform having a trough structure and a sub-unit coupled to the trough structure. The trough structure is defined on a surface of the platform and is configured for the transmission of an optical beam through the trough structure. The sub-unit has a surface that is configured to mate with the trough structure to provide a chosen alignment on the platform in order to emit, operate on, or receive the optical beam.
The sub-unit may comprise a plurality of sub-units, each of which is coupled to the trough structure for transmitting, operating on, or receiving the optical beam. The sub-units may include a submount having a lower surface and the lower surface has a protrusion with a contour. The trough structure also has a contour that is configured to precisely mate with the contour of the protrusion. The module may further comprise at least one recess for accepting a joining member of a sub-unit. The joining member may be an electrical contact.
The trough structure may have side walls that are sloped at an angle, and the protrusions may have side walls that are sloped at an angle that is complementary to the angle of the trough structure side walls. The sub-units may include a plurality of electrical contacts. The platform may include a plurality of recesses for accepting the plurality of electrical contacts from the sub-units. The plurality of recesses and contacts are precisely positioned to provide the chosen alignment. A recess may be defined on the platform for accepting a filter. The platform surface may be flat and the trough structure may have a bottom surface that is flat.
The sub-unit may include a submount having a lower surface and the lower surface may have a protrusion with a contour. The platform surface is flat and the submount lower surface is flat, other than the protrusion. The sub-unit may comprise a plurality of sub-units, and the plurality of sub-units may comprise a laser diode, an attachable optical fiber connector, and at least one photodiode. The at least one photodiode may comprise a photodetector chip, a lens, a submount, and a cap. The device may also include an optical filter associated with the photodiode, with the cap being for alignment of the filter on the submount. The photodiode is preferably configured to receive a signal at at least one wavelength from an optical beam.
The attachable optical fiber connector comprises a submount, a decollimating unit, and a fiber, with the fiber fixedly coupled to the submount. The attachable optical fiber connector may alternatively comprise a connector, a decollimating unit, and a fiber, with the fiber fixedly coupled to the connector, and the connector having a contour for seating in the trough structure.
The platform may be silicon. Alternatively, the platform may comprise a base portion and an insert, with the trough structure being defined in the insert. The base portion may be plastic and the insert may be silicon.
In another embodiment, an opto-electronic module comprises a platform and a plurality of sub-units. The platform has a trough structure defined on a surface thereof and the trough structure is configured for the transmission of an optical beam. The plurality of sub-units is coupled to the platform. The sub-units are configured to emit, operate on or receive the optical beam. The platform and plurality of sub-units are together configured to provide angular alignment of the sub-units on the platform in both a vertical plane and a horizontal plane for the transmission of an optical beam between the plurality of sub-units.
Each of the plurality of sub-units may have at least one protrusion and the protrusions may be configured to precisely seat in the trough structure to couple the plurality of sub-units to the platform. The platform may include recesses and the sub-units may include members for seating in the recesses, with both the trough structure and the recesses being utilized for coupling the sub-units to the platform and for aligning the sub-units on the platform.
The plurality of sub-units comprise at least one optical component. The at least one optical component comprises a laser diode, a fiber connector, a filter, and a photodiode. The plurality of sub-units may also include at least one electrical component. The at least one electrical component may comprise a chip.
In yet another embodiment, a module for converting a collimated beam of light into an electrical signal comprises a substrate and a plurality of optical components. The substrate has a recessed path for transmitting a collimated beam of light. The optical components are associated with the recessed path for emitting, operating on, or receiving the collimated beam of light to convert a beam of light to an electrical signal or convert an electrical signal to a beam of light. At least one electrical component may also be associated with the substrate. The plurality of optical components may comprise a laser diode, a fiber connector, at least one photodiode, and at least one filter, and the at least one electrical component may comprise a laser driver chip.
With reference now to the drawings, the example opto-electronic device 10 is utilized to convert a fiber optical signal to an electrical signal. The example device 10 comprises a module of individual sub-units 12, which can either emit, operate on, or receive a collimated laser beam of light. The collimated beam of light carries a signal at one or more wavelengths. This signal may be in the form of voice, video, data, or otherwise. The opto-electronic device 10 takes incoming light energy and separates it into separate wavelengths, where more than one wavelength of energy is present. The device 10 also takes electrical signals and converts them to a beam of light in order to transmit a signal from a user's house. The sub-units 12 are optically interconnected to other sub-units 12 by the collimated beams. The interconnecting beams of light are less sensitive to alignment tolerances normal to the beam. As a result, the example opto-electronic device 10 may be assembled with techniques that do not require the precise positioning of prior art assemblies.
The sub-units 12 depicted in
The filters 28, 30 are beamsplitters and the photodiodes 34, 36 are receivers. Although separate components, the first optical filter 28 is typically packaged with the first photodiode sub-unit 34 and the second optical filter 30 is typically packaged with the second photodiode sub-unit 36. In particular, each package includes an alignment cap 38 that covers both the photodiode 34, 36 and the associated filter 28, 30, and the photodiode submount 35. In the embodiment of
The attachable fiber connector sub-unit 32 is connected to a fiber optic cable 40. The fiber sub-unit 12 may include a submount 33, as shown in
The lens 52 must be accurately positioned in the photodiode submount 35 and fixed in the two lateral planes normal to the optical axis Z-Z. Positioning of the lens 52 along the optical axis Z-Z is controlled by the placement of the lens 52 with respect to the edge of the submount 35. Contacting the lens 52 on this edge sets the focal distance. Alignment in the two lateral planes X-X, Y-Y normal to the optical axis Z-Z is accomplished by moving the lens 52 over the edge surface and registering the direction of the beam when the opto-electronic device is emitting. The lens 52 is fixed by a layer of light curing adhesive (not shown) and is cured when the correct alignment of the beams is achieved.
A trans-impedance amplifier (TIA) chip (not shown) is preferably coupled to the photodiode for receiving the electrical current from the photodiode, filtering noise out of the signal, and amplifying the signal. The signal coming from the photodiode is typically weak and noisy. Therefore, it is advantageous to locate the TIA as close as possible to the photodiode on the module. The microbench structure described herein makes the integration process of the TIA with the photodiode fairly easy and is fully automated due to the modular design of the microbench.
In a preferred embodiment, as shown in
The trough structure 16 provides an avenue for the transmission of the collimating beam. In addition, the trough structure 16 provides a thermal path for more efficient heat dissipation and distribution than with prior art solutions. Heat will spread through the troughs 16 and travel directly to the external electrical leads 42. This design has a reduced tolerance to alignment in directions normal to the beam, but requires exact angular alignment.
The components on the microbench 10 operate together to receive information into the home and transmit information from the home. The incoming signal enters the microbench 10 from outside the home in the form of a collimated beam of light via the fiber optic cable 40, which is coupled to the attachable optical fiber connector sub-unit 32. The signal may be at a single wavelength, or multiple wavelengths. Optical energy travels from the fiber 40 through the trough structure 16 to the filters 28, 30. The filters 28, 30 are utilized to split the beam of light into different wavelength signals. For instance, a portion of the beam of light that includes voice and data may be included in a first wavelength signal while a portion of the beam of light that includes video may be included in a second wavelength signal. The light is split via the first and second filters 28, 30, which are angled relative to the beam of light. The filters 28, 30 allow some light to pass through and reflect the remainder in the desired wavelength. The first filter 28 directs the first wavelength to the first receiver (the first photodiode) 34 via the trough structure 16. The second filter 30 directs the second wavelength to the second receiver (the second photodiode) 36 via the trough structure 16. The reflected light is collected in the photodiodes 34, 36 and converted to an electrical signal for use in the home. The electrical signal is then transferred to a circuit board (not shown) that is coupled to the microbench 10 via the electrical connectors 42 positioned on the microbench 10.
For an outgoing signal that is leaving the home, information travels to the laser diode 26 as an electrical signal from the circuit board to the microbench 10 via electrical connectors 42 positioned on the microbench 10. The laser diode 26 and a laser driver chip together convert the electrical signal into an optical signal in the form of a collimated beam of light. This light travels through the trough structure 16 through the filters 28, 30 and is collected by the attachable optical fiber connector 32, which includes a decollimating unit that focus the light into the fiber 40. The signal leaves the microbench 10 through the fiber cable 40.
The example microbench 10 is for use in optical interface units (OIU's) that utilize two or three port optical devices, such as duplexers and triplexers, among other uses. The example depicted in
Assembly of the system requires the placement of sub-units 12 into their respective positions and a fix procedure involving a straight forward bond with a joining material, such as a solder or an epoxy. The joining material may also act as an electrical interconnect.
The trough structure 16 in the platform 14 may be formed in a number of different ways. The platform 16 and troughs 16 may be formed integrally during a molding process, such as injection molding. The electrical lead structures 42, 48, 50 can be incorporated directly into the platform 14 during the molding process. The platform 14 and trough structure 16 may be integrally formed from a plastic or silicon material, among other materials. The platform 14 may be formed of a plastic material and a silicon layer can be applied to the troughs 16, if desired. In another embodiment, the troughs 16 may be formed as a separate insert by a precision photolithographic process, and the insert may then be embedded in the platform structure 14 by standard insert molding processes. The troughs 16 may be formed of a first material, such as silicon, and the platform 14 may be formed of a second material, such as plastic. The use of a different trough material can add to the mechanical stability of the platform structure 14, and offer a precision trough structure 16 for accepting the sub-units 12.
The use of a trough structure 16 offers a trough with sloping walls 24 for alignment of the sub-units 12 when they are lowered into the trough 16. This offers a larger placement target for assembly and simplifies the process. Final angular alignment in the horizontal plane occurs when the protrusion 20 enters the trough 16 and engages against the side walls 24. The joining material provides the down force necessary to maintain the alignment of the sub-units 12 in the trough 16. The system provides a basis for many different configurations for opto-electronic pathways. Other designs for the protrusions 20 and troughs 16 may be utilized.
The example microbench 10 can be used for either duplexer or triplexer architecture. First stage amplification for the digital and/or analog receiver can be integrated into the design. The microbench 10 is surface mountable, e.g., mountable directly on a circuit board. This is advantageous because the present design does not require that any parts extend through the circuit board, as with prior devices, such as with the Triport BIDI®. This improves the performance on the circuit board and makes the assembly process easier and less expensive.
The assembly is preferably designed for operation at a temperature range of −40 C to 85 C and is mass producible using standard chip placement machines, such as pick-and-drop machines. Because the production process may be automated, the assembly provides a reduced package size at a lower cost than current designs, and has a high performance level of 2.5 Gbps. The system provides a basis for many different configurations of opto-electronic pathways.
The example architecture allows the direct integration of monolithic or chip level electronic circuitry, such as laser drivers and receiver circuitry. It is low cost and highly integratable. While the above-described embodiments are discussed in the context of FTTH applications, the example microbench 10 has applications in many areas of telecommunications, including long-haul, metro, and access markets. It can be utilized in dense wavelength division multiplexing (DWDM), wavelength division multiplexing (WDM) (dual wavelength), and single wavelength applications where high performance, low cost opto-electronic devices are utilized.
The term “flat”, as used herein, means flat or substantially flat, where substantially is used as an estimation term.
While various features of the claimed embodiments are presented above, it should be understood that the features may be used singly or in any combination thereof. Therefore, the claimed embodiments are not to be limited to only the specific embodiments depicted herein.
Further, it should be understood that variations and modifications may occur to those skilled in the art to which the claimed embodiments pertain. The embodiments described herein are exemplary. The disclosure may enable those skilled in the art to make and use embodiments having alternative elements that likewise correspond to the elements recited in the claims. The intended scope may thus include other embodiments that do not differ or that insubstantially differ from the literal language of the claims. The scope of the example embodiments is accordingly defined as set forth in the appended claims.
