Embodiments of the present invention relate generally to decreasing the cost and increasing the reliability of optical communication networks. More specifically, embodiments of the present invention monitor the output of light emitting sources and detect failure or potential failure of the light emitting sources.
Operators of optical networks including fiber optic communication networks often want to know the operational status of various systems and system components in the network, including the functional status of optical communication components such as optical transmitters, receivers, and transceivers. Knowing the operational status aids the operators in identifying components of the network that may need to be repaired or replaced. In the case of transmitters/transceivers in optical communications, the light producing components (sources), such as vertical-cavity surface-emitting lasers (VCSELs), may begin to malfunction or not emit light that meets the designed capabilities of the VCSEL or corresponds to the power being supplied to the VCSEL.
Embodiments of the present invention utilize an array of light emitting sources, an array of photodiodes, and a controller to measure the light produced by the light emitting sources and detect potential failures of the light emitting sources. In one example embodiment, an assembly for monitoring output of a light emitting source (LES) is provided. The assembly includes an array of lenses, an array of LESs, wherein each LES is configured to emit light towards a lens in the array of lenses, an array of photodiodes, arranged to receive light reflected off of the array of lenses, wherein each photodiode is configured to generate a photo-induced current in response to receipt of the light reflected off the array of lenses, and a controller. In some examples, the controller is configured to measure the photo-induced current from each photodiode in the array of photodiodes, and determine a change in operational status of one or more of the LESs based on the photo-induced currents.
In some cases, the array of LESs and the array of photodiodes form a coupled pair, and the controller is further configured to receive a value indicative of a power consumption of each LES, correlate the power consumption of each LES with a measured photo-induced current in each photodiode, determine a coupling matrix for the coupled pair, and determine an inverted matrix by inverting the coupling matrix.
In some examples, the controller is further configured to determine a photo-induced current matrix from updated measured photo-induced currents from each photodiode, and multiply the inverted matrix and the photo-induced current matrix to form a LES output matrix, wherein the LES output matrix represents an ongoing light output from each LES.
In some cases, the controller is further configured to determine, from the LES output matrix, one or more LESs experiencing a failure event based on an ongoing light output lower than a predetermined expected value from the one or more LESs.
Additionally, in some examples, the failure event comprises a failing LES and the lower ongoing light output comprises a light output lower than a predetermined expected value.
In some cases, the failure event comprises a failed LES and the lower ongoing light output comprises no light output.
In some examples, a position of the array of photodiodes relative to the array of LESs comprises at least one of a lateral offset, a vertical offset, or a distance offset between the array of photodiodes and the array of LESs.
In some additional examples, the assembly includes one or more transimpedance amplifiers configured to amplify the photo-induced currents from the array of photodiodes.
In some cases, the array of LESs comprises an array of vertical-cavity surface-emitting lasers.
In accordance with another example embodiment, a method for monitoring output of a light emitting source (LES) is provided. In some examples, the method includes measuring a photo-induced current induced in one or more photodiodes in an array of photodiodes, arranged to receive light reflected off of an array of lenses, wherein the light is emitted by an array of LESs configured to emit light towards the array of lenses, and wherein each photodiode is configured to generate the photo-induced current in response to receipt of the light reflected off the lenses, and determining a change in operational status of one or more of the LESs based on the photo-induced currents.
In some examples of the method, the array of LESs and the array of photodiodes form a coupled pair, and the method further includes receiving a value indicative of a power consumption of each LES in the array of LESs, correlating the power consumption of each LES with a measured photo-induced current in each photodiode. The method also includes determining a coupling matrix, and determining an inverted matrix by inverting the coupling matrix.
In some examples, the method further includes determining a photo-induced current matrix from updated measured photo-induced currents from each photodiode, and multiplying the inverted matrix and the photo-induced current matrix to form a LES output matrix, wherein the LES output matrix represents an ongoing light output from each LES.
In some cases, determining a change in the operational status of one or more of the LESs based on the photo-induced currents further includes determining, from the LES output matrix, one or more LESs experiencing a failure event based on an ongoing light output lower than a predetermined expected value.
In some additional examples, the failure event comprises a failing LES and the lower ongoing light output comprises a light output lower than a predetermined expected value.
In some examples of the method, the failure event comprises a failed LES and the lower ongoing light output comprises no light output.
In some examples, each photo-induced current comprises an amplified photo-induced current.
In some cases, the array of LESs comprises an array of vertical-cavity surface-emitting lasers.
The above summary is provided merely for purposes of summarizing some example embodiments to provide a basic understanding of some aspects of the invention. Accordingly, it will be appreciated that the above-described embodiments are merely examples and should not be construed to narrow the scope or spirit of the invention in any way. It will be appreciated that the scope of the invention encompasses many potential embodiments in addition to those here summarized, some of which will be further described below.
Having thus described the invention in general terms, reference will now be made to the accompanying drawings, which are not necessarily drawn to scale, and wherein:
The present invention now will be described more fully hereinafter with reference to the accompanying drawings, in which some, but not all embodiments of the inventions are shown. Indeed, these inventions may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that this disclosure will satisfy applicable legal requirements. Like numbers refer to like elements throughout. As used herein, relational terms such as “above,” “below,” “parallel,” etc. are used for explanatory purposes in the examples provided below to describe the relative position of certain components or portions of components to other components or portions.
As noted above, operators of optical networks often desire to know the operational status of the optical communication components. One way to verify that these components are functioning properly is to measure the light that is coming out of the light-producing components. Conventional methods for measuring the light require a tap or other structures, such as altered lenses, to divert light towards a photodiode to measure the light produced. Such methods automatically result in lower light (as much as 30% lower) for use in the optical functions requiring the light. Additionally, designing and updating structures, including lens structures, to redirect light for measurement can be expensive and time consuming.
To optimize the use of the light emitted by the light producing components and to reduce the expense of designing and implementing light redirecting structures, the inventors have designed an assembly and method to determine the light output by light emitting sources in a communication network by measuring light reflected off of the lens without the use of additional structures.
Turning now to
As shown, the assembly 100 may include an array of light emitting sources (LESs) 104. The array of LESs 104 may be configured to emit light towards an array of lenses 108, such that each LES in the array of LESs 104 emits light 110 towards a lens 106. For example, as further illustrated in
As shown in
According to some embodiments, a certain amount of the light 110 emitted towards the lens 106 will be reflected off of the lens. In an example using a polyetherimide lens, the surface of the lens 106 in the array of lenses 108, may reflect approximately 6% of the light 110 emitted towards it from a light source in the array of LESs 104. The unreflected light 112 will pass through the lens 106 and can be used for further functions, such as fiber optic communication.
Referring back to
Due to the nature of light and reflections, the photodiodes 302a-302d will be affected by a certain level of crosstalk, or light reflected off of the other lens in the array of lenses. For example, when the array of photodiodes 102 is functioning normally, the photodiode 302b will receive some level of light reflected off of the lens 106 as shown in
To optimize the positioning of the array of LESs 104 and the array of photodiodes 102, the inventors have discovered that certain position parameters should be followed, as shown in
Turning to
Turning again to
Turning again to
For example
As shown in
As shown in block 804, monitoring circuitry 606 in the controller 120 may be configured to determine a change in the operational status of one or more of the LESs based on the photo-induced currents. In some examples, the change in operational status may be the failure of one or more LES in the array of LES 104. This step is described in more detail in relation to
As shown in block 814, the monitoring circuitry 606 in the controller 120 may be configured to correlate the power consumption of each LES with a measured photo-induced current in each photodiode. In some examples, the array of photodiodes and the array of LESs form a coupled pair, and the correlation may include a determination that the photo-induced current is equal to the power consumption of the LESs multiplied by a coupling matrix G as shown in Equation 1.
As shown in block 816, the monitoring circuitry 606 in the controller 120 may be configured to determine a coupling matrix for the coupled pair. For example, a coupling matrix such as coupling matrix G shown in
As shown in block 816, the monitoring circuitry 606 in the controller 120 may be configured to determine an inverted matrix by inverting the coupling matrix. In some embodiments, in order to determine the output of the LESs from a measurement of the photo-induced currents, the coupling matrix G must be inverted as shown in Equation 2.
G
−1
In some examples, the monitoring circuitry 606 is also configured to store the coupling matrix G and/or the inverted matrix G−1 in the memory 604 for later use or for use as a standard coupling or inverted matrix. In some examples, the operations of
As shown in block 824, the monitoring circuitry 610 of the controller 120 may be configured to multiply the inverted matrix G−1 described above and the photo-induced current matrix to form a LES output matrix, where the LES output matrix represents an ongoing or periodically updated light output from each LES. In some examples, the inverted matrix G−1 is the inverted matrix G−1 described in the operations of
As shown in block 826, the monitoring circuitry 610 of the controller 120 may be configured to determine, from the LES output matrix, one or more LESs experiencing a failure event based on a lower ongoing light output of the LES as compared to a previously determined or expected light output for the same LES. In some examples, the failure event may be a failing LES, where the lower ongoing light output comprises a light output that is lower than a predetermined value. The predetermined value may, for example, be an expected output for the particular type of LES (e.g., based on its design specifications),taking into account the amount of current consumed by the LES, and/or the temperature of the LES. In some cases, the predetermined value may be provided by the manufacturer of the LES, whereas in other cases the predetermined value may be calculated or experimentally derived based on various factors such as the current consumed by the LES, the temperature of the LES, and/or other external factors that may affect the power consumption. For example, in some cases, the predetermined value may be an average of a historical light output for the given LES over a period of time during which the LES is in operation (e.g., the previous month). Thus, for a failing LES, the LES output matrix may show one of the LESs as outputting less light than expected. For example, if the LES 204a is producing less light than expected, such as an output of 0.8 μA where the predetermined or expected value is 1 μA, p1 in
In some examples, upon detection of the failure event, the communication circuitry 608 in the controller 120 may be configured to transmit a notification warning to an operator that a failure event has been detected at a particular LES.
Thus the operations and assembly described herein provide a reliable and efficient method to monitor a failure event of a light emitting source. For example, if a VCSEL in an optical transceiver in a fiber optic network continues to consume power in the form of electric current but the light output from the VCSEL is decreasing, the induced current in the photodiodes described herein will decrease, and the controller in the assembly will determine based on the coupled pairing which of the VCSELs is experiencing the decreased output. Upon determination of the problem in the VCSEL, the controller 120 will notify an operator of the affected optical transceiver. This will provide the operator of the fiber optic network early notification of potential failures in the network and allow for preventative or ongoing maintenance.
Many modifications and other embodiments of the inventions set forth herein will come to mind to one skilled in the art to which these inventions pertain having the benefit of the teachings presented in the foregoing descriptions and the associated drawings. Therefore, it is to be understood that the inventions are not to be limited to the specific embodiments disclosed and that modifications and other embodiments are intended to be included within the scope of the appended claims. Although specific terms are employed herein, they are used in a generic and descriptive sense only and not for purposes of limitation.