The present invention generally relates to the field of optical fiber splicing, and more specifically, to apparatuses and methods directed to mechanical splice termination and evaluation of resulting splice joints.
When working in the field of fiber optics, users are often required to establish connections between non-connectorized ends of optical fibers or fiber ribbons. This is generally referred to as splicing and typically involves creating temporary or permanent joints between two (or sometimes more) fibers. In certain instances, the two fibers are precisely aligned and then fused together using localized intense heat often times created with an electric arc. This is referred to as fusion splicing and is widely employed to create high performance permanent joints between two optical fibers. However, a fusion splicer apparatus can be bulky, expensive, and relatively fragile. Alternatively, the two fibers may simply abut one another in an alignment fixture often referred to as a mechanical splice. The alignment fixture may be an alignment tube or V-groove which receives two ends of separate fibers on either side and has the means to physically secure the fibers. In other instances, the alignment device may be a fiber optic connector with a stub fiber embedded therein made to be connectorized to a field fiber. In this case the field fiber can be terminated utilizing a mechanical splice to the stub fiber inside the connector. An example of the fiber optic connector with an embedded stub fiber is illustrated in
To avoid loss of signal and reduce the potential reflectance or light leakage within these joints, users must ensure that the fiber(s) are properly cleaved, that there is precise alignment between the fibers, and that transparent gel or optical adhesive applied between the fibers matches the optical properties of the glass. However, these details are not always easy to detect and/or ensure. Therefore, there is a continued need for apparatuses and methods directed towards helping to determine and improve the quality of mechanical splices and provide improved termination of fibers such as field fibers.
Accordingly, at least some embodiments of the present invention are generally directed towards helping to determine and improve the quality of mechanical splices of optical fibers, and provide methods and apparatuses to assist in fiber termination.
In an embodiment, the present invention is an apparatus for evaluating the integrity of a mechanical splice joint, and comprises a light source, digital video camera, digital signal processor, and visual indicator, wherein the apparatus connects to the test connector and the digital signal processor analyzes digital images of the scatter light from at least a portion of the test connector.
In another embodiment, an apparatus according to the present invention includes a Bluetooth or other wireless communication interface to enable communication to a portable or handheld device such as a smartphone, wherein the portable device contains a resident application for providing a user interface to said apparatus and may also include splice analysis software and/or firmware.
In yet another embodiment, the present invention is a method for evaluating the integrity of a mechanical splice joint, wherein the method includes the steps of coupling light into a test connector and a field fiber, and, evaluating digital images of a scattered light pattern from at least a portion of the mechanical splice joint and the optical fibers.
In still yet another embodiment, the present invention is an apparatus for installing a field fiber in a fiber optic connector having a stub fiber therein and/or evaluating at least one characteristic of a splice between the stub fiber and the field fiber, at least a portion of the fiber optic connector being at least one of transparent or translucent. The apparatus includes a light source, the light source injecting a light into the fiber optic connector via the stub fiber, some of the injected light radiating through the fiber optic connector. The apparatus also includes a digital camera, the digital camera capturing a digital image of the fiber optic connector. Additionally, the apparatus includes a digital processor, the digital processor using the digital image to evaluate light radiating through the fiber optic connector to determine the at least one characteristic of the splice.
In still yet another embodiment, the present invention is a method of installing a field fiber in a fiber optic connector having a stub fiber therein and/or evaluating at least one characteristic of a splice between said stub fiber and said field fiber, at least a portion of said fiber optic connector being at least one of transparent or translucent. The method includes the steps of: (i) mating said fiber optic connector with a test apparatus; (ii) injecting a light from a light source into said fiber optic connector via said stub fiber, some of said injected light radiating through said fiber optic connector; and (iii) using a digital camera to evaluate light radiating through said fiber optic connector to determine said at least one characteristic of said splice.
These and other features, aspects, and advantages of the present invention will become better understood with reference to the following drawings, description, and any claims that may follow.
As used herein, the term “metric” shall be understood to mean any mathematical relationship which represents the behavior or optical radiation at any desired point or any desired collection of points within a particular fiber optic connector as it relates to the connector's insertion loss. In at least some embodiments of the present invention, the selected metrics have a relatively high correlation to the connector's insertion loss. Furthermore, for the sake of convenience and ease of visualization, digital images reproduced herein have been presented as negatives rather than positives.
Mechanical splicing can occur when a field optical fiber is connectorized to a pre-manufactured fiber optic connector with a stub fiber embedded therein. The particular example of
At least some embodiments of the present invention provide a means of determining and improving the quality of mechanical splices as utilized in pre-polished fiber optic connectors for terminating single-mode and multimode optical fibers in the field. One such embodiment (shown in
This apparatus can aid in joining a prepared field fiber 102 to a stub fiber inside a test connector 100. To use said apparatus, the test connector 100 is positioned such that splice joint 103 is located approximately within the central field of view of the digital video camera 202. Light source 201 includes a semiconductor laser (or any other suitable optical radiation generation source) capable of emitting light having a spectral range within the optical sensitivity of the video camera, typically between about 400 nm and about 1700 nm. The light source is capable of launching light into the stub fiber when engaged with the test connector.
During and after the installation of the field fiber 102 into the optical fiber mechanical splice joint of the test connector 100, the apparatus continuously captures images of the scattered light pattern and analyses the digital images from at least two regions of the test connector which include, but are not limited to, splice joint 103 and the buffered field fiber 102. An example of a digital image for a partially inserted field fiber is shown in
It has been observed that the optical power radiated from the stub fiber connectors may not be an accurate metric to characterize the IL. Due to variations during the connectorization, the power reaching the photodetector from multiple connector regions can suffer significant fluctuations. Accordingly, at least some embodiments of the present invention rely on the geometry of the radiated light as it travels through and scatters from the connector 100 to determine quality of a splice joint.
where in the presently described embodiment min(ima(x,y)) is 2 and max(ima(x,y)) is 154.
Next the metric parameters and ratios of selected zones are computed 406. For example an image profile can be described by equation (2), the centroid of the image can be described by equation (3), and the uniformity around the centroid can be described by equation (4).
By integrating the relative optical radiation at each horizontal pixel along the connector, the image profiles give an indication of the leaking light from different locations of the connector. The centroid and uniformity (i.e., standard deviation of pixels) give an indication of how the test connector's geometry and material properties affects the leaking light. Furthermore, since various types of connectors have various types of light leakage profiles, by comparing to known profiles, the uniformity of the pixels, U(x), described in equation (4) can also be utilized to identify connector types and/or improve the location of the zones of interest. Equations (2)-(4) are just examples of various parameters that can be computed to characterize the image. For the images of
To determine the quality of the splice, one can compare specific zones of the test connector (for example as defined in
where K is an optional arbitrary constant, with value of 40 in this example for normalization purposes.
The selection of the metrics can depend on the connector type and imaging setup. For the connector and setup utilized in the currently described embodiment, ratio R1 compares the splice joint region 103 to the field fiber region 102, and ratio R2 compares the splice joint region 103 to stub fiber region 101.
The metric values are evaluated against predetermined limits. These limits may be selected such that any particular metric falling within the established limit is deemed to signify an acceptably high probability that the insertion loss for a particular connector is less than or equal to a preferred level. Performance data which may be helpful in determining an accurate limit may be obtained by way of statistical analysis of various test connector configurations.
Since the degree of probability may be user-dependent, the predetermined limits may vary causing the system to be more or less stringent. In the presently described embodiment, metrics R1, R2, and Um are evaluated against limits L1, L2, and L3, respectively. Accordingly, L1, L2, and L3 have been selected such that any respective R1, R2, and Um values which fall within those limits will indicate a sufficiently high probability that the insertion loss for the test connector is ≤0.5 dB. Note that inclusion within a limit depends not only on whether a metric value is above or below some limit value, but also on whether the particular limit is an upper or a lower limit. This will vary for different metrics. In the currently described embodiment, R1 and R2 are upper limits and Um is a lower limit. Thus, R1<L1, R2<L2, and Um>L3 satisfy these limits.
The values of R1, R2, and Um, (along with their respective predetermined limits L1, L2, and L3) for the connectors tested in
Referring back to
In the presently described embodiment, all three metrics, R1, R2, and Um, are evaluated by way of the following equation:
D=W(R1<L1)+W2(R2<L2)+W3(Um>L3) (8)
Note that equation (8) is merely exemplary and other equations may be derived and used if so desired. If R1 is within the limit of L1 (i.e., less than L1) then the evaluation of R1 against L1 is set to a value 1; otherwise it is set to 0. This result is then multiplied by the weight W1. If R2 is within the limit of L2 (i.e., less than L2) then the evaluation of R2 against L2 is set to a value 1; otherwise it is set to 0. This result is then multiplied by the weight W2. If R3 is within the limit of L3 (i.e., greater than L3) then the evaluation of R3 against L3 is set to a value 1; otherwise it is set to 0. This result is then multiplied by the weight W3. The summation of weighted metric evaluations is then compared against a predetermined threshold, TD, which is proportional to the probability of producing a correct final decision. If D>TD, the probability that IL<ILmax is sufficiently high and therefore the splice joint is acceptable. Otherwise a failure indicator 204 can be activated, and the fiber is reterminated 408 and the splice is thereafter reevaluated 406, 407.
By way of an example, two test connectors shown in
D=60(0.143<L1)+20(65.527<L2)+30(1653.574>L3) (9)
D=60(1)+20(0)+30(1) (10)
D=90 (11)
Thereafter, D is compared against the threshold TD (which for the purposes of this example is assumed to be 80). Since (90>80) is true, the probability that IL is less than the maximum allowed IL is adequately high and therefore the splice joint is acceptable. Note that sole reliance on the R2 metric would have eliminated this termination as acceptable even though the actual IL value is 0.26.
For connector of
D=60(0.22<L1)+20(45.078<L2)+30(1703.023>L3) (12)
D=60(0)+20(0)+30(1) (13)
D=30 (14)
Thereafter, D is compared against the threshold TD. Since (30>80) is false, the probability that IL is less than the maximum allowed IL is insufficiently low and therefore the splice joint is unacceptable. Note that sole reliance on the Um metric would have deemed this termination acceptable even though the actual IL value is 0.58.
It should be noted that the aforementioned method can operate with one or more video cameras or additional imaging systems such as mirrors to capture images from opposite views of the connector splice joint. However, in some embodiments it may be preferable to use connectors with light-diffusing material. Therefore, one camera may be enough to provide an accurate estimation of the insertion loss based on the captured images.
A convenient and potentially cost effective embodiment of the present invention is to use a smartphone or other wireless device to control and view test results of the disclosed apparatus. The use of a personal handheld device may reduce the cost and size of the test apparatus by allowing at least a part of the application/use interface portion to run on the handheld device via an application which may be downloaded from an internet website. Furthermore, the handheld device may communicate with the test apparatus by means of Bluetooth, Wi-Fi, or other suitable wireless communication protocol.
In an embodiment, the makeup of the test apparatus can include a smartphone and an adapter. This can allow one to take advantage the hardware typically installed in the smartphone, using the smartphone's digital camera and digital processor for the digital camera and digital processor, respectively, of the test apparatus. In addition, an adapter having a light source therein can be connected to the phone. Such adapter may draw power directly from the smartphone and be activated by a test application executed on the smartphone. Such configuration may provide significant cost savings over a dedicated test apparatus and may be more desirable in some cases.
Note that while this invention has been described in terms of one or more embodiments, these embodiments are non-limiting (regardless of whether they have been labeled as exemplary or not), and there are alterations, permutations, and equivalents, which fall within the scope of this invention. For example, any number of zones of interest may be used for the evaluations of the splice joints and those zones may be defined in any way suitable for a particular application. Likewise, any number of metrics may be used to evaluate the properties of the splice, and those metrics may be defined by any suitable equation and/or relationship. Thus, while the described embodiments have presented a particular example of what is defined as any specific zone and any specific metric, those zones and metrics should not to be construed as limiting in any way. Additionally, the described embodiments should not be interpreted as mutually exclusive, and should instead be understood as potentially combinable if such combinations are permissive. It should also be noted that there are many alternative ways of implementing the methods and apparatuses of the present invention. It is therefore intended that claims that may follow be interpreted as including all such alterations, permutations, and equivalents as fall within the true spirit and scope of the present invention.
Furthermore, the subject matter described herein, such as for example the methods for testing the integrity of a splice joint in accordance with the present invention, can be implemented at least partially in software in combination with hardware and/or firmware. For example, the subject matter described herein can be implemented in software executed by a processor. In one exemplary implementation, the subject matter described herein can be implemented using a non-transitory computer readable medium having stored thereon computer executable instructions that when executed by the processor of a computer control the computer to perform steps of a method or process. Exemplary computer readable media suitable for implementing the subject matter described herein include non-transitory computer-readable media, such as disk memory devices, chip memory devices, programmable logic devices, and application specific integrated circuits. In addition, a computer readable medium that implements the subject matter described herein may be located on a single device or computing platform or may be distributed across multiple devices or computing platforms. Devices embodying the subject matter described herein may be manufactured by any means, such as by semiconductor fabrication or discreet component assembly although other types of manufacturer are also acceptable, and can be manufactured of any material, e.g., CMOS.
This application is a continuation of U.S. patent application Ser. No. 14/920,270, filed Oct. 22, 2015; which claims the benefit of U.S. Provisional Patent Application No. 62/077,433 filed on Nov. 10, 2014, which is incorporated herein by reference in its entirety.
Number | Date | Country | |
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62077433 | Nov 2014 | US |
Number | Date | Country | |
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Parent | 14920270 | Oct 2015 | US |
Child | 16055923 | US |