|Publication number||USRE42845 E1|
|Application number||US 12/370,441|
|Publication date||Oct 18, 2011|
|Filing date||Feb 12, 2009|
|Priority date||Mar 1, 2002|
|Also published as||US6803562, US20030164448|
|Publication number||12370441, 370441, US RE42845 E1, US RE42845E1, US-E1-RE42845, USRE42845 E1, USRE42845E1|
|Inventors||David R. Ohm, Richard A. Booman|
|Original Assignee||Null Networks Llc|
|Export Citation||BiBTeX, EndNote, RefMan|
|Patent Citations (8), Non-Patent Citations (5), Classifications (14), Legal Events (5)|
|External Links: USPTO, USPTO Assignment, Espacenet|
This application is a reissue divisional of U.S. application Ser. No. 11/546,489 filed Oct. 10, 2006, now abandoned, which is a reissue application of U.S. application Ser. No. 10/087,877, filed Mar. 1, 2002 (now patented as U.S. Pat. No. 6,803,562) and entitled “Indirect Monitoring of Semiconductor Light Source Within a Photonic Package.” The current application claims priority to U.S. application Ser. No. 10/087,877 via U.S. application Ser. No. 11/546,489. The specification of U.S. application Ser. No. 11/546,489 is hereby fully incorporated by reference.
The invention relates to the field of photonic packaging. More specifically, the invention relates to monitoring of a semiconductor light source within the photonic packages.
With advances in integrated circuit, microprocessor, networking and communication technologies, an increasing number of devices, in particular, digital computing devices, are being networked together. Such devices are often first coupled to a local area network, such as an Ethernet-based office/home network. In turn, the local area networks are interconnected together through wide area networks, such as Synchronous Optical Networks (SONET), Asynchronous Transfer Mode (ATM) networks, Frame Relays, and the like. Of particular importance is the TCP/IP based global internetwork, the Internet. The rapid growth of the Internet has fueled a convergence of data communication (datacom) and telecommunication (telecom) protocols and requirements. It is increasingly important that data traffic be carried efficiently across local, regional and wide area networks.
The widespread deployment of high-speed networking and communications equipment has produced a large demand for various types of networking and communications components and subsystems. Included among these, are modules, which are often referred to as optical transponders.
Optical transponders typically include components for both electrical signal processing, and components for transmission and reception of optical signals. Conventional optical transponders typically receive data representing electrical signals in parallel, serialize the data represented, encode the serialized data onto a light-based signal, and couple that optical signal to an outbound optical fiber. Similarly, conventional optical transponders, typically receive a light-based signal having data serially encoded thereon, recover the data in an electrical form, de-serialize the data and provide them in a parallel format to a plurality of output terminals.
Conventional optical transponders typically include a case, or housing, within which the electrical and optical components are enclosed. Such a housing provides physical protection for the components therein, and also provides thermal conductivity so that heat may be dissipated from the components disposed within the case. The number of components may be numerous. However, a requirement of the housing is that the housing be of a small form factor. Accordingly, in order to have the components within a housing of a small form factor, placement of the components is an important aspect of the optical transponder.
Placement of the components may be determined by one component's operation relative to another's. For example, as described above, a component, such as a semiconductor light source, that operates to provide light-based signals is placed in such a manner as to be optically coupled to another component, such as an optical fiber, that operates to optically transmit light-based signals.
Integrity of the light-based signals and stability of the semiconductor may be based upon power output of the semiconductor light source. Accordingly, an important component of an optical transponder is semiconductor light source monitoring device, such as a photodetector, that can monitor the power output of the semiconductor light source. Due to design of a common semiconductor light source used in optical transponders, the semiconductor light source can provide light in more than one path, e.g., two light paths, simultaneously. One light path, commonly known as light source facet, is directed to the optical fiber. Another light path, commonly referred to as back facet, may be directed to a light receiving area of the photodetector. The photodetector receives the light via the light receiving area, or window, and the light is converted to electrical signals, which are sent to another component to be processed to determine the integrity of the light-based signals and stability of the semiconductor light source (i.e., optical power, temperature, and the like). This monitoring is commonly referred to as back-facet monitoring (BFM). The light source facet and the back facet are on opposite sides of each other. Accordingly, placement of the photodetector is opposite side of the semiconductor light source coupled to the optical fiber.
As the form factor of the housing of the optical transponder continues to become smaller, placement of the photodetector in the light path opposite the optical fiber side of the semiconductor light source becomes increasingly difficult due to various components included in the housing.
The invention is illustrated by way of example and not by way of limitation in the figures of the accompanying drawings, in which the like references indicate similar elements and in which:
The invention facilitates indirect monitoring of a semiconductor light source by a photodetector within a photonic package. In the following description, various aspects of the invention will be described. However, one skilled in the relevant art will recognize that the invention may be practiced without one or more of the specific details, or with other methods, materials, components, etc. In other instances, well-known structures, materials, or operations are not shown or described in detail to avoid obscuring aspects of various embodiments of the invention. Similarly, for purposes of explanation, specific numbers, materials and configurations are set forth in order to provide a thorough understanding of the invention. Nevertheless, the invention may be practiced without the specific details. In other instances, well-known features are omitted or simplified in order not to obscure the invention. Furthermore, it is understood that the various embodiments shown in the figures are illustrative representations and are not necessarily drawn to scale.
Reference throughout this specification to “one embodiment” or “an embodiment” means that a particular feature, structure, material, or characteristic described in connection with the embodiment is included in at least one embodiment of the invention. Thus, the appearances of the phrases “in one embodiment” or “in an embodiment” in various places throughout this specification are not necessarily all referring to the same embodiment or invention. Furthermore, the particular features, structures, materials, or characteristics may be combined in any suitable manner in one or more embodiments.
For the purposes of describing the invention, lightwaves will be illustrated as straight lines. However, one skilled in the relevant art will appreciate that lightwaves may behave as waves or particles. Additionally, certain established principles of physics will not be described in detail, in particular, derivations of equations such as those describing the behavior of semiconductors and the like will not be described in detail. However, relevant equations will be described but not derived.
Accordingly, the concept of data carried by lightwaves will not be described in detail. However, for the purposes of the invention, the concept of utilizing different wavelengths of lightwaves to carry different data will be referred to in describing the invention.
For the illustrated embodiment, substrate 102, when viewed from the top, is substantially trapezoidal in shape, with side surface 105 being the surface disposed on an angular side of the trapezoidal substrate 102. In alternate embodiments, substrates of other shapes may be employed, including but not limited to triangle, rectangle, and polygon, so long as the disposition orientation of the substrate results in its surface of the side next to semiconductor light source 101 being angularly disposed relative to the back light facet of semiconductor light source 101. Further, back wall 105 may be provided by other non-substrate component, to be described in further detail below.
Continuing to refer to
In order to describe the invention, references will be made to an exemplary area 110 & 350 (an area around the semiconductor light source).
Illustrated also in
For example, the photodetector 205 may be a p-i-n junction photodiode, where spectral responsivity may be expressed as
In Equation 1, I is amperes of current generated by the photodetector 205, and L is power of incident light, the reflected light 210, measured in watts. R is responsivity in units of amperes per watt. Furthermore, external quantum efficiency of a photodiode is its capability to convert light energy to electrical energy (i.e., electrical signals), and can be expressed as a relation to responsivity as
where EQE (λ) is external quantum efficiency as function of wavelength, I is photocurrent (output current—dark output current) as function wavelength, h is Planck's constant, c is velocity of light, Φ is input radiant flux (power), n is index of refraction of air, e is elementary charge, and λ is wavelength of light in units of nanometers. Accordingly, the Equation 1 and Equation 2 can be utilized to form the relationship
where R and λ, as defined earlier, are responsivity in units of amperes per watt and wavelength of light in units of nanometers, respectively.
The electrical signals may be provided to the processor wherein the electrical signals may be compared to characterization data. The characterization data may relate electrical signals from the photodetector 205 produced by reflected 210 light received by the photodetector 205 of the first output 201 of the light source 101. For example, referring to
As a result, a photodetector can be adapted to receive light reflected from a surface of a component disposed at the back of the semiconductor light source, housed inside a densely populated housing of an optical transponder, thereby advantageously monitoring a semiconductor light source from locations other than those that are directly behind the semiconductor light source (i.e., the photodetector is not required to be in direct path of the back output of the semiconductor light source).
In one embodiment, the interior surface of the cover 303 may have a coating to help facilitate cover reflected light 305, such as, but not limited to, paint having a pigment of titanium dioxide (i.e., white paint).I
In one embodiment, the reflective mirror surface 301 may be a highly polished silicon mirror or a dielectric coating. In alternative embodiments, it may be a reflective sheet or stripe.
Alternatively, in one embodiment, the reflective mirror surface 301 may be disposed in such a manner as to reflect the second output 202 from the back facet 103 of the light source 101 to one or more other secondary reflective surfaces, such as, but not limited to, a side wall of horsing (not shown). For these embodiments, the photodetector will be adapted accordingly in a coordinated manner to receive light reflected from the alternate secondary reflective wall by positioning the receiving window of the photodetector to face the alternate secondary reflective wall.
As a result, alternate interior surfaces of a housing of an optical transponder may be utilized to provide reflected light to a photodetector adapted to receive the reflected light.
Thus, it can be seen from the above descriptions, a novel method and apparatus for indirect monitoring of a light source by a photodetector, has been described.
The above description of illustrated embodiments of the invention, including what is described in the Abstract, is not intended to be exhaustive or to limit the invention to the precise forms disclosed. While specific embodiments of, and examples for, the invention are described herein for illustrative purposes, various equivalent modifications are possible within the scope of the invention, as those skilled in the relevant art will recognize. Thus, the description is to be regarded as illustrative instead of restrictive on the invention.
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|1||Interview Summary, issued in U.S. Appl. No. 11/546,489, mailed Jul. 7, 2008.|
|2||Notice of Allowance, issued in U.S. Appl. No. 10/087,877, mailed Jun. 10, 2004.|
|3||Office Action, issued in U.S. Appl. No. 10/087,877, mailed Mar. 18, 2004.|
|4||Office Action, issued in U.S. Appl. No. 10/087,877, mailed Oct. 2, 2003.|
|5||Office Action, issued in U.S. Appl. No. 11/546,489, mailed May 1, 2008.|
|U.S. Classification||250/239, 250/216, 257/433, 257/432|
|International Classification||H01J5/02, H01L31/0232, H01J40/14, H01S5/022, H01S5/0683|
|Cooperative Classification||H01S5/0683, H01S5/02208, H01S5/02248, H01S5/0071|
|Jan 10, 2011||AS||Assignment|
Owner name: NULL NETWORKS LLC, NEVADA
Free format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNOR:TRIQUINT SEMICONDUCTOR, INC.;REEL/FRAME:025611/0449
Effective date: 20050908
Owner name: NETWORK ELEMENTS, INC., OREGON
Free format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNORS:OHM, DAVID R;BOOMAN, RICHARD A;REEL/FRAME:025611/0264
Effective date: 20020301
Owner name: TRIQUINT SEMICONDUCTOR, INC., OREGON
Free format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNOR:NETWORK ELEMENTS, INC.;REEL/FRAME:025611/0345
Effective date: 20041217
|Nov 1, 2011||CC||Certificate of correction|
|May 1, 2012||CC||Certificate of correction|
|May 28, 2012||REMI||Maintenance fee reminder mailed|
|Oct 14, 2012||LAPS||Lapse for failure to pay maintenance fees|