Patent Description:
Embodiments of the claimed invention relate to the field of optical fiber mechanical splice joint insertion loss estimation.

Current and future applications requiring high bandwidth channels favor the utilization of fiber optics links. Installation of fiber optic links can utilize pre-terminated or field terminated connectors. In the pre-terminated case, pre-specified fiber cable lengths are connectorized in the factory, where connectors are machine polished, tested, and certified to provide high performance. Field terminated links can follow different approaches: termination and polishing the connector in the field, utilize pre-terminated pigtails that can be spliced to the fiber link, or mechanical splice connectors. Field termination and polishing is unpractical and typically cannot match the quality of factory-polished connectors. Splicing factory terminated pigtails to the fiber link is a better approach which involves creating temporary or permanent joints between two fibers. In certain instances, the two fibers are precisely aligned and then fused together using localized intense heat oftentimes 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, fusion splicer apparatuses are usually bulky, expensive, and relatively fragile, and splice joints must be protected and managed, typically in splice management trays or enclosures.

Alternatively, the mechanical splice connectors can provide low cost, fast installation, and high quality performance. In this approach 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, channel, or V-groove which receives two ends of separate fibers on either side and has the means of physically securing the fibers in place. In other instances, the alignment device may be a fiber optic connector with a stub fiber embedded therein and designed to connectorize a field fiber. In this case the field fiber can be terminated utilizing a mechanical splice to the stub fiber inside the connector.

In order to avoid significant loss of signal and reduce the potential reflectance or light leakage within these joints, users must ensure the field fiber is properly cleaved, there is precise alignment between the field and stub 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. This uncertainty can result in connectors that have insertion loss (IL) values that exceed specified limits of the channel and therefore make them unsuitable for the required reaches, data rate, or bit error rate (BER) application.

A common used approach to ensure that the channel IL meets the specification, is to test the complete channel after installation. A measurement of the IL can be done using a power meter with methods shown in TIA or IEC standards, e.g., TIA, OFSTP-<NUM> for single mode fiber (SMF) and IEC <NUM>-<NUM>-<NUM> for multimode fiber (MMF). Alternatively, the channel can be tested using an optical time domain reflectometer (OTDR), which uses the backscatter signature of the fiber to make an indirect measurement of fiber and connector losses. While OTDRs require only termination in one side of the link, they typically have poor spatial resolution making it difficult to resolve the discrete losses of closely space connectors, and are relatively expensive devices. Moreover, OTDRs have several technical disadvantages. They require a long launch cable to mitigate the dead-zone effects, and can have significant inaccuracies due to the mismatch in fiber light backscattering, diameter, and mismatch in numerical apertures of the fibers used in the link. To improve the OTDR's accuracy, measurement from both sides of the link are required. However, this negates its main advantage of performing measurements from one end of the cable.

Therefore, there is a need for apparatuses and methods directed towards helping to reduce cost and improve channel performance of the fiber optics link.

Document <CIT> describes 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.

Document <CIT> describes apparatuses and methods directed to mechanical splice termination and evaluation of resulting splice joints.

The invention to which the present European patent relates is defined in the appended claims.

Accordingly, disclosed herein are embodiments directed towards methods as claimed in the appended claims which assist and guide an installer during the termination of a field optical fiber to a field-terminable connector, and help determine and record IL after termination.

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.

Mechanical splicing often occurs when a field optical fiber is connectorized to a premanufactured fiber optic connector with a stub fiber embedded therein. An example of such a connector is shown in <FIG>. Connector <NUM> generally includes a ferrule holder <NUM> with a ferrule <NUM> positioned at the front end thereof, and a top plank <NUM> and a bottom plank <NUM> positioned between the ferrule <NUM> and a distal end <NUM> of the connector. The connector <NUM> includes a stub fiber <NUM> which is typically embedded in the optical connector at the time of manufacture. The stub fiber <NUM> extends from the outer edge of the ferrule (which can later interface a corresponding adapter) to the inner portion of the connector in the general area of the top and bottom planks <NUM>, <NUM>. To splice the stub fiber <NUM> with a field fiber <NUM>, a user inserts the field fiber into the connector <NUM> through its distal end <NUM>, aligns both fibers accordingly, and activates a cam <NUM> to clamp the field fiber and the stub fiber in place, forming a stub fiber / field fiber interface <NUM> (also referred to as a splice joint). Ensuring that light leakage and reflection are reduced or minimized at these joints is essential for a well-executed splice. Accordingly, the present invention may help a user with proper splicing of two fibers.

<FIG> shows an apparatus which can help a user terminate a field fiber to a pre-polished connector stub fiber and test the quality of the resulting splice joint. The termination and test apparatus comprises an electronic driver <NUM> to generate continuous or pulsed signals to a visible or infrared light source, an LED or laser device <NUM> that launches light to an optical fiber ferrule using free space optics, such a lenses, diffractive elements, or using a launch optical patch cord, an optical filter <NUM> which can operate as a band-pass filter for specific regions of the optical spectrum, e.g., <NUM>, an optical lens or diffractive element <NUM> to direct and focus the light towards an imaging device such as a camera sensor, an array of optical detectors, or a digital video camera <NUM>, which can optionally have the infrared stopband filter removed and the infrared bandpass filter attached, a microcontroller or processor <NUM> for image acquisition and for controlling all functionalities of the apparatus, including a user input device, e.g., a keyboard <NUM>, or an output device such as a visible or audible transducer <NUM> and <NUM>, respectively. An apparatus may also include a display unit to assist the user during the installation process and to indicate a pass/fail termination condition. The apparatus may also have provisions for communicating with other devices by means of a Bluetooth, Wi-Fi, or other wireless device <NUM>, using wireless communication protocols for remote control and/or uploading connector installation data.

The connector under test <NUM> is positioned such that splice joint <NUM> is located essentially within the field of view of digital video camera <NUM>. Light source <NUM> can include a semiconductor laser capable of emitting light having a spectral range within the optical sensitivity of the video camera, typically between about <NUM> to <NUM> for visible operation or between <NUM> to <NUM> for infrared operation. The optical source is capable of launching light into the stub fiber when engaged with the connector under test. When the user turns on the device, power is supplied to all necessary power-consuming components such as, but not limited to, the light source <NUM>, digital video camera <NUM>, processors and electronics <NUM>, <NUM>, and user visual/sound interface <NUM>, <NUM>. The spatial pattern of the scattered light emanating from multiple regions of the connector <NUM> passing through the filter <NUM> and focusing optics <NUM> is imaged by video camera <NUM> and the images are analyzed by <NUM> utilizing digital signal processing algorithms disclosed in this application.

The prepared field fiber <NUM> can be joined to the stub fiber inside test connector <NUM> with the assistance of the presented apparatus and method. While field fiber <NUM> is being inserted, the apparatus continuously captures images of the scattered light pattern and analyses the digital images from at least two regions of the test connector <NUM> which includes splice joint <NUM> and the field fiber <NUM>. <FIG> shows a typical image <NUM> of an OptiCam® LC connector <NUM>, captured using an <NUM>-bit black & white camera with 640x480 x-y pixel resolution. For the configuration represented here, only <NUM> pixels along the y-axis are considered.

As a field fiber is inserted, a series of images at different stages of the termination process are captured, corrected and analyzed by the apparatus in order to provide real-time monitoring, termination assistance, and IL estimation. <FIG> shows a flow chart representative of an exemplary method used to assist during installation and to evaluate the connector insertion loss.

The process shown in <FIG> starts in step <NUM> when the equipment is turned on by the operator. In <NUM>, the apparatus runs an initialization routine which includes checking the proper operation of its electronic components such as microcontroller, camera, laser output level, flash memory, etc. In <NUM> the main parameters used in the algorithms of the method are loaded into local memory. These parameters can include variable assignation for each type of connectors, calibration constants, default resolution of the camera, default exposure time, default gain, default frame rate, noise thresholds, x-y coordinate for locations in the sensor to compute dark current, x-y coordinate for reference points in the sensor, decision threshold for image localization, decision thresholds for tilt correction, initial scaling factors, decision thresholds for RTC acceptance for each type of connector, decision and threshold factors for illumination, sleeping time constants, variables for maximum number of iterations in RTC process, and many others. In <NUM>, the apparatus displays a message indicating the apparatus is ready for operation and provides the operator with the option to change default values such as connector type, pass/fail spec limits, or other relevant parameters. If necessary, in <NUM> the operator uses an input device to change one or more default parameters. In <NUM> the operator receives a display message to insert the pre-terminated optical connector and connect the optical source to the connector ferrule. At this point, the user also has the option to terminate the process.

In <NUM> the apparatus runs algorithm A1, which checks the environmental ambient illumination levels without laser illumination, and compares levels to threshold levels already loaded in <NUM>. This is done by measuring the background levels of ambient light reaching the sensor. If the measurement is greater than a specified threshold, the apparatus outputs a message indicating that a cover is needed to shade the connector (or ambient light needs to be reduced in some other manner) in order to accurately estimate low insertion loss values. Under most operating conditions of at least <NUM> lux for indoor illumination (fluorescent or LED lighting devices), the threshold value is high enough to enable operation without a cover.

Next, in <NUM> the apparatus runs algorithm A1, which checks the background noise in non-illuminated areas of the sensor. The noise level of the optical imaging system is estimated by analyzing a small region of the sensor that is not illuminated by external optical sources. Then, the maximum and standard deviation of the noise, as well as the histogram is estimated. The noise is recorded as a variable, i.e., NOISE_TH, in memory and used by other algorithms as a threshold to clean the image.

Next in step <NUM>, the position, tilt and scale factors of the connector image in the sensor are estimated using algorithm A3. In order to reduce manufacturing and assembly costs, the mechanical tolerances of the apparatus such as lateral and angular offsets, height, sensor and lens relative position, length defocus, and scaling factors can be relaxed. Hence, prior to step <NUM> the precise location and orientation of the image on the sensor, and the exact value of these parameters are unknown. The self-alignment algorithm, represented in the flow chart of <FIG>, is used to locate the position of the connector image on the sensor, correct for any lateral offsets or axial tilt, and estimates the visual magnification of the object with respect to its image in the sensor. The parameters obtained from this algorithm are required for the subsequent algorithms shown in the chart of <FIG> for accurate image analysis and connector performance estimation.

Referring to <FIG>, the estimation of these parameters begins in step <NUM>, where the noise of the sensor, NOISE_TH, which was estimated during the execution of algorithm A2, is used to determine a threshold required to identify the location of the connector in the sensor, labeled here THRESHOLD_P0. For example, a factory calibration factor, (loaded in step <NUM>) can be used to multiply the parameter NOISE_TH.

In step <NUM> the camera is set to the maximum exposure time and in step <NUM> two images are captured. The first image is acquired with the optical source turned off. This image is labeled background image. The second image capture occurs with the optical source turned on. The later image is labeled foreground image. Next, the background image is subtracted from the foreground image resulting in a resultant image. An example of each of these images is shown in <FIG>. In step <NUM> the effects of noise in the image analysis are minimized by setting all pixels with level values below the NOISE_TH to zero. In step <NUM> the y-axis profile or vertical profile of the image is computed using: <MAT> where, I(x, y) is the image array. An example of the PV(y) calculation is shown in <FIG>.

In <NUM> the centroid of PV(y) is computed using:
<MAT>
or alternatively using cent_y = maxy(PV(y)).

In step <NUM>, the value of cent_y is used to select the region of interest (ROI) in the sensor that covers the image of the connector along the y-axis. This reduces the number of y-axis pixels to be utilized in the subsequent computations. For example, for a sensor with 640x480 pixels, after the y-axis ROI is found, only <NUM>×<NUM> pixels are used. Next, in <NUM> the profile average of the image is computed using: <MAT> where, IROI (x, y) is now the ROI selected from the sensor image. The start and end of the connector image is computed using the following procedure:.

Then, in step <NUM>, the centroid(x) and width(x) are computed using: <MAT> <MAT> and the number of pixels that represent the connector in the sensor is computed using: <MAT> Thereafter, the ratio of n_pixels with a design parameter loaded in <NUM> are used to computer the scaling factor. <MAT> The value of the design parameter assumes an apparatus with tight tolerances, where the image is in focus. The scaling factor is stored and to be used by the RTC and IL algorithms (A6 and A7). In the next steps, which is the tilt estimation algorithm, it is assumed that the object plane is tilted with respect of the sensor plane as shown in <FIG>. This figure shows the centroid(x) and width(x) computed in <NUM>.

In step <NUM>, the slope of the centroid(x) is computed using:
<MAT>
and in step <NUM>, the angle of tilt, angle_d is computed from the slope using: <MAT> where, ANGLE_BIAS is a factory calibration parameter loaded from memory in step <NUM>.

Next, in step <NUM>, if the tilt angle is larger than a maximum tilt angle, a flag variable, FLAG_ANGLE_CORRECT, is turned on. This flag will be used in algorithm A4; when ON it will correct for the tilt, if OFF it will not make a correction. In step <NUM>, if FLAG_ANGLE_CORRECT is turned on, the image will be corrected. This is an optional step to show the degree of correction before the termination of the connector is performed. <FIG> shows and example of tilt correction. In step <NUM>, the algorithm ends and returns to the general flow chart shown in <FIG> and to step <NUM>.

Referring back to <FIG>, in steps <NUM> the apparatus runs algorithm A4 which captures images with corrected background and enhanced dynamic range. To be more specific, image processing is required to extract the information from the acquired images in order to predict if the connector is ready to be terminated while the fiber is inserted, and after termination, to estimate the IL. In order to reduce the cost of the apparatus, an uncooled B&W CMOS camera with relative low resolution, e.g., 640x480 pixels, may be utilized. The effective number of bits per pixel is relative low (e.g., <NUM> bits). The algorithm illustrated by way of a flow chart in <FIG> is able to efficiently extract key information from the images captured by the camera. This information is used later for the ready to cam algorithm (RTC, A6) and for the IL estimation (algorithm A7).

<FIG> shows the flow diagram algorithm A4. Beginning in step <NUM>, the algorithm finds the best exposure time that sets the levels inside the range of pixel levels obtained in step <NUM> of <FIG>. For example, for an <NUM>-bit per pixel B&W camera, the range of levels can be <NUM> to <NUM>. A correct execution of this step is important to the other algorithms since an incorrect exposure time will produce underexposed or saturated images. The algorithm follows an iterative cycle which continuously modifies the exposure based on current maximum values in the image. For example, the new exposure is obtaining by multiplying the current exposure by a factor that is directly proportional to the maximum pixel level (e.g., <NUM> for an eight-bit camera) and inversely proportional to the current maximum level. After the correct exposure is obtained, the image is captured in step <NUM>. Since the apparatus performs real-time background subtraction in order to operate without a cover under most of the indoor illumination conditions, ideally at least two images are captured during this step. First, the optical source is turned off, and an image is acquired and labeled as background image. Next, the optical source is turned on and a second image, labeled foreground image, is acquired. Finally, the background image is subtracted from the foreground image. As a result of this processing, the impact of the environmental lighting is reduced or minimized. The resultant image is labeled low exposure image.

Next in step <NUM>, the exposure is set to the maximum value which, in most cases, produces saturation in at least one pixel. In step <NUM>, the resultant image is captured in a similar way as described above for the low exposure image. The light source is turned off to capture a background image and turned on to capture a foreground image. The images are subtracted and the resultant image is stored and labeled high exposure image.

In step <NUM> both images are combined to produce an image with high dynamic range. The algorithm can use the following equation for the combination:
<MAT>
where, Ic(x, y) is the image array in the apparatus's memory, τLOW and τHIGH are the low exposure time (obtained in step <NUM>), and the highest exposure time of the camera respectively. In equation (<NUM>), Threshold_comb is a predefined parameter loaded in step <NUM> of <FIG>, which depends on the camera characteristics. An example for this combination is shown in <FIG>.

Next in step <NUM>, the effect of noise is reduced by using: <MAT> where, NOISE_TH was determined in step <NUM> using algorithm A2.

In step <NUM>, the algorithm corrects for the misalignment detected by algorithm A3. For example, if there is a tilt in the image and if FLAG_ANGLE_CORRECT is ON, (see algorithm A3) the image is corrected. <FIG> shows an example for this correction. In step <NUM>, the image is reduced from a <NUM>-dimensional array to a one-dimensional array or vector, denominated here as a profile. This reduction is done to enable real-time computations of RTC and IL algorithms without requiring an expensive and/or power consuming processor. The profile shown in <FIG>, as an example, are denominated profile average PA(x) and profile maximum PM(x), and are computed from the images I(x, y) from equation (<NUM>) using: <MAT>.

After computation, the profiles are stored in memory and in step <NUM>, and the A4 algorithm ends and return control to other processes as shown in <FIG>.

Referring back to the flow chart of <FIG>, in step <NUM> algorithm A5 runs a check to determine if the optical source is sufficiently coupled to the connector under test. Insufficient optical coupling results in a low signal-to-noise ratio (SNR) and inaccurate IL estimations. To help determine the integrity of the connection, this algorithm evaluates the ratio of intensity levels of different regions of the connector. In order to estimate these ratios, it uses the profiles, PA and PM stored in memory from previous steps in the general method. As an example, the following equations can be used for the computation of ratios:
<MAT>
<MAT>.

The position of the regions B and C are obtained from pre-loaded tables (obtained in step <NUM>) for the type of connector. As an exemplary illustration, one can use the profiles shown in <FIG>, where region B is the area close to the interface between the launch fiber and the beginning of field connector determined by x-pixels <NUM> to <NUM>, and region C can be determined by x-pixels between <NUM> and <NUM>. After the ratios are computed using equations (<NUM>) and (<NUM>) they are compared with pre-loaded thresholds. Depending on the comparison it will be determined if the connection between the launch fiber and the field connector is sufficiently good. If the connection is sufficiently good, a flag variable will be activated and a message can be displayed to show the status of the connection. Otherwise, a message to disconnect the source and clean may be displayed.

Referring back to <FIG>, in step <NUM> the apparatus saves the profiles obtained in step <NUM> as initial connector profiles. For illustration purposes, the average maximum profiles at this step will be saved as PAl(x) and PM2(x).

Next, in step <NUM> the operator receives a message to insert the prepared field fiber into the connector and upon insertion of the connector, the apparatus continues the RTC algorithm A6 in steps <NUM> to <NUM>.

More specifically, algorithm A6 is designed to assist the operator during the termination process. It outputs an indicator when the connector is ready to be cammed such that the splice is completed. In step <NUM> algorithm A4 is called to process the image and provide the profiles, PA(x) and PM(x). As explained earlier, algorithm A4 will capture, correct for background illumination, correct for misalignments, and enhance the dynamic range before returning the profiles.

In step <NUM> the centroids of both profiles and their ratios for certain regions are computed in a similar way as described in algorithm A5. The regions of importance for the RTC algorithm are preloaded for each connector type, e.g., LC or SC. These regions may be determined from statistical analysis of a large population of connectors. <FIG> shows an example for <NUM> SC connectors labeled SC1 - SC4.

Three stages of the RTC image analysis are shown in <FIG>. In part (a) the field fiber is only partially inserted and the connector is not ready to be cammed, avoiding a high IL (> 1dB) condition. In part (b), the field fiber is in close proximity to the internal stub fiber, but not yet in the optimum position. In part (c) the images show when the field fiber is fully inserted and in physical contact with the internal stub fiber. Once this condition is achieved, the connector is ready to be cammed. For a connector cammed during this condition, there is a high likelihood that that the IL is very low (e.g., <<NUM> dB).

<FIG> also shows that the peak levels of the radiation patterns shift from region C to D as the field fiber approaches the stub fiber. This visual effect can be quantified with the centroid of the image or with the ratio of average levels between regions C and D. The computational method for the later metric is given by:
<MAT>.

To provide continuous feedback to the user, in step <NUM> the apparatus can communicate real time values of the ratio or centroid by transmitting the calculated numerical values or pictorial representations to a display, in the form of graphical images or progress bars.

In <NUM>, the algorithm compares the ratios and centroid with preloaded thresholds (loaded in <NUM> for the type of connector). This threshold may come from a statistical analysis for each type of connector. If the centroid is higher than the centroid threshold and the RTC condition is achieved, the algorithm will proceed to step <NUM>. Otherwise, it will return to step <NUM> and the RTC cycle will repeat. In step <NUM>, the profiles are stored as PA2(x) and PM2(x) and thereafter in step <NUM> a message and/or image can be displayed indicating that the connector termination can be completed by camming or rotating the mechanical splice mechanism. Once done so, the RTC process is ended in step <NUM> with the last profile from the RTC process being stored in step <NUM>.

Next, in step <NUM>, algorithm A5 again verifies that the optical source is properly coupled to the connector. If not, a flag variable is activated and a message is displayed instructing the user to reposition and or clean the mating points. If algorithm A5 verifies a properly coupled optical source, step <NUM> captures and stores a new set of IL profiles. Then, in step <NUM> the connector parameters,.

(connector profiles, RTC profiles, and IL profiles) are saved in order to maintain records of the installation process.

Thereafter, in step <NUM> algorithm A7 is executed to estimate the IL of the connector. This algorithm is utilized to estimate IL based on captured images at different stage of the installation process. The algorithm is based on statistical studies of a large population of connectors of different types, such as LC and SC for single-mode and multimode connectors. The insertion loss value determined pursuant to this algorithm will be estimated using: <MAT> where, K_IL1, K_IL, K_IL2, K_IL3, K_IL4, and K_IL5 are factory calibration factors loaded in step <NUM>, and SUM_C1, SUM_C2, SUM_C3 and SUM_B3 are defined as: <MAT> <MAT> where, i is an index that can take values from <NUM> to <NUM>. The fundamentals of this algorithm are described below and an exemplary illustrations of the algorithm performance are shown in <FIG>.

In once the IL is estimated, in step <NUM> the value returned by algorithm A7 is compared against the specified limit from default tables loaded in step <NUM>, or against values entered by the operator in step <NUM>. If the IL is lower than the specified limit (e.g., <NUM>. 75dB) a true logic condition is generated and pass indicator <NUM> will be displayed along with the estimated IL value on the display screen. If a false condition occurs, a "fail" message will be displayed in step <NUM>. In the earlier case, the IL results are saved in step <NUM> and the process ends at step <NUM> where the tool enters a "Tool Ready" stage essentially equivalent to the stage after step <NUM>. In the latter case, the process proceeds directly to step <NUM>.

After finalizing the termination process the profiles at three stages of the installation, as well as the IL and time are saved. This information can be used later for statistical analysis. The advantage of saving the profiles instead of the images is that the memory requirements on the tool can be reduced at least <NUM> orders of magnitude and data transmission from apparatus to a mobile device can become faster.

The disclosed apparatus can operate in stand-alone mode during the complete installation. The installer ID, time, location and profiles for each connector can be stored in the apparatus. However, in order to perform technical and managerial analysis of the installation project, the aggregate data from several apparatuses maybe required. For this purpose, the apparatus can include functionalities to connect to a mobile device in a wired or wireless configuration, e.g., Bluetooth. The mobile device can send data to update the tool tables and update the firmware among other functionalities. The mobile device can also upload the data stored in the tool or transmit to a centralized data base where analysis can be performed.

A computer or mobile device with access to the aggregate data of one or more installation projects can analyze the data and provide valuable information to the installer, customer, or connector supplier to be used to improve:.

In some cases, it may be desirable to have a computer control, display, and provide sound outputs accordingly to the status of the termination process. In the general method shown in <FIG>, the display and sound algorithm is executed in steps <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, and <NUM>. <FIG> show some examples of the images to be displayed. For example, during the RTC algorithm (A7) <FIG> can show figures of the connector with a color bar indicator representing how close the field fiber is to the stub fiber. At the optimum position, the display will show (like in <FIG>) that the fiber is ready to terminate or cam and it will show a message to rotate the connector. Alternatively, when the installation conditions make it difficult to see the display, a sound from a speaker in the apparatus or a headphone (wired or wireless) connected to the apparatus can emit a sound to indicate if the connector is ready to terminate. <FIG> shows an exemplary image of a display after the IL is estimated by the apparatus using algorithm A7 in step <NUM>.

Claim 1:
A test method for evaluating the optical insertion loss of a mechanical splice joint of two optical fibers (<NUM>, <NUM>), comprising:
using an apparatus comprising a laser source (<NUM>), digital video camera (<NUM>), a microcontroller or processor (<NUM>), electronic circuitry, resident memory, and means for coupling the laser output signal to one of the optical fibers to be spliced;
capturing and analysing digital video images of the scattered light from at least a portion of one optical fiber and the mechanical splice joint using embedded algorithms in order to determine the quality of the mechanical splice;
providing dynamic range enhancement of the camera sensor and providing background subtraction of ambient light in order to improve the estimation of the mechanical splice joint's optical insertion loss based on real-time image analysis of the mechanical splice joint;
providing a pass/fail numerical, pictorial or audible indication (<NUM>, <NUM>) of the optimum position to terminate the splice joint in order to assist an operator during the splice joint termination process; and
estimating the optical insertion loss of the mechanical splice joint based on the captured images,
characterized in that said
providing dynamic range enhancement of the camera sensor comprises an algorithm, comprising the steps of:
determining an optimal exposure time for the capturing of images;
taking a background image of the mechanical splice joint with the laser source turned off;
taking a foreground image of the mechanical splice joint with the laser source turned on;
subtracting the background image from the foreground image to obtain a resultant image;
estimating the level of noise by analysing an area of a sensor that is not illuminated by external sources and reducing the effect of noise by zeroing the pixels with level values below the estimated level of noise in the resultant image;
estimating a tilt and correcting for the tilt in the resultant image; and
reducing the resultant image from a <NUM>-dimensional array to a one-dimensional array or vector.