This disclosure relates generally to optical transceivers, and, more particularly, to optical transceivers and methods to reduce interference in optical transceivers.
Telecommunication, computer networking and other applications have increasingly moved toward fiber optic connections as the push for speed and increased bandwidth has proceeded. This move toward optical networking has given rise to increased demand for optical components. At the same time, the ever present desire for miniaturization has increasingly led to locating components in close proximity to one another in increasingly small packages. Packing electronics in close quarter has led to cross-talk and electromagnetic interference (EMI) problems.
Known ways to suppress noise producing microwave emissions (and, thus, EMI) in transceivers includes shielding electrically noisy components with grounded housings, or grounding the component case itself to prevent such emissions. However, such prior art solutions require significant area on the printed circuit board (PCB) for grounding moats, etc. and are, thus, not consistent with the desire to miniaturize. Further, in some applications, the case/package of the noisy component cannot be grounded because it must be electrically isolated or biased to a non-zero voltage.
An example prior art optical transceiver is shown in
The example transceiver of
Typically, the output signals of the ROSA 24 are very weak. Therefore, they are very susceptible to interference. As shown in
In order to reduce cross-talk and/or other EMI originating with the laser diode driver 22, the transceiver 100 is provided with an absorber 102. In the illustrated example, the absorber 102 is a broadband absorber which defines a cavity dimensioned to receive the laser diode driver 22 when the absorber 102 is positioned upon the PCB of the transceiver 100. The height of the absorber 102 is preferably selected to be at least as tall as the laser diode driver 22. Thus, the absorber 102 surrounds the sides of the driver 22 to thereby suppress EMI emissions from the driver 22 to reduce electromagnetic interference with surrounding components such as the communication line 26.
Unlike prior art approaches to EMI suppression which required dedicated PCB area for the EMI suppression components (e.g., grounding moats, etc.); the absorber 102 can be employed without consuming any PCB real estate or requiring expansion of the PCB. Instead, the absorber 102 is structured to overlie at least a portion of the transmit chain 16 and at least a portion of the receive chain 18. In the illustrated example, the absorber 102 surrounds the laser diode driver 22, while overlying a portion of the electrical connector/driver line 104 coupling the converter 12 to the laser diode driver 22, overlying a portion of the electrical connector 106 coupling the laser diode driver 22 to the TOSA 20, and overlying a portion of the differential communication link 26 coupling the ROSA 24 to the converter 12 to thereby reduce interference between the emissions of the driver 22 and the communication link 26. In an example implementation of the circuit of
An example implementation of the transceiver 100 of
As mentioned above, the material of the absorber 102 is preferably selected to absorb microwave emissions. Thus, the absorber 102 is preferably a microwave absorber. The absorber 102 may be implemented by a Ferrite absorber. For instance, the absorber 102 may be implemented by a broadband absorber such as the ECCOSORB FGM from Emerson & Cuming or the MAGRAM (ferrite) DD from Arc Technologies.
Although the illustrated examples include a monolithic absorber 102, persons of ordinary skill in the art will readily appreciate that the absorber 102 may be implemented using two or more components. These multiple components may or may not be physically joined or fixed together.
As mentioned above, the absorber 102 is preferably positioned to overlie at least a portion of the transmit chain 16 and at least a portion of the receive chain 18. However, as shown in
Optical transceivers 100 such as those described above may be manufactured by at least partially positioning a converter 12, a transmit chain 16 and a receive chain 18 on a printed circuit board. As discussed above, the transmit chain 16 will typically include a laser diode driver 22 and a TOSA 24. The receive chain 18 will typically include a ROSA 24 to transmit signals to the converter 12 via a differential signal line 26. The transmit chain 16 and the receive chain 18 may be generally parallel to one another.
Subsequently, one or more broadband absorbers 22 are positioned on the PCB such that collectively the absorber(s) at least partially overlie the receive chain 18 and at least partially overlie the transmit chain 16. As discussed above, the absorber(s) 102 preferably define a cavity 110 to receive the laser diode driver 22. The cavity 110 is preferably not closed, such that the manufacturing process can be advanced by thermocoupling the driver 22 to a heat sink such as the transceiver housing.
From the foregoing, persons of ordinary skill in the art will appreciate that optical transceivers and methods of reducing interference in optical transceivers have been disclosed. The disclosed transceivers utilize one or more broadband absorbers to reduce interference between noisy components and components exhibiting low signal strength levels. The absorber(s) are preferably designed to overly one or more portions of the transceiver's PCB and may include one or more cavities to receive and preferably surround noisy components. Because the absorber(s) overlie the PCB, they need not be secured to, printed on or embedded in the PCB, and, thus, do not utilize PCB real estate.
Persons of ordinary skill in the art will readily appreciate that the optical transceivers disclosed herein may be used in a wide range of systems for a wide range of applications. For example, an optical transceiver constructed in accordance with the principles described herein may be used in a communications network to transmit voice or data signals received from a host device. To this end, the transceiver may be coupled to a host device via, for example, a parallel or serial bus.
Although certain example methods, apparatus and articles of manufacture have been described herein, the scope of coverage of this patent is not limited thereto. On the contrary, this patent covers all methods, apparatus and articles of manufacture fairly falling within the scope of the appended claims either literally or under the doctrine of equivalents.