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Fiber End Face Interferometer![]()
GL16 All-in-One Interferometer (Example Cable Not Included) 3D Scan of 12-Fiber Linear Array in MT-Style Ferrule 3D Scan of Single Mode Fiber in FC/PC Connector ![]() Please Wait Features
Thorlabs' GL16 End Face Interferometer measures and images the end face geometry of single- and multi-fiber connectors. A non-contact technique called scanning white-light interferometry (SWLI) provides high accuracy, repeatability, and reliability for fiber connector testing, particularly for pass/fail testing using IEC or Telcordia requirements. The system can be controlled locally through the touchscreen display or remotely through a browser-based application (see Software tab for details), allowing it to be easily integrated on the production floor. All the system components are fully integrated in the enclosed housing. A wide-bandwidth 570 nm LED light source is used with a Michelson interferometric objective lens to measure the phase shift for step height changes as large as 35 µm. A piezoelectric stage moves the interferometric objective lens relative to the connector and collects the resultant interference patterns using a high-resolution camera. A 3D height map of the connector surface is created and then used to calculate the fiber geometry parameters with lateral resolution of 2.2 µm and height resolution of 1.1 nm (see Measurement tab for details). White-light interferometry is able to characterize undercut or protruded fibers that would be missed using a monochromatic interferometer (see Interferograms tab for details). The included GL16M4 MT-style fixture enables 8-second measurement of up to 72 fibers at a time in 12-fiber-row ferrules. The GL16 interferometer is capable of measuring a variety of additional fiber types and connector styles (shown in the table below) by swapping out the included fixture. Choose the appropriate mounting assembly below for your connector type and the number of fibers to be measured.
![]() Click to Enlarge Interferometric scans are used to measure the fiber and connector geometry and compare the results against a database of industry-standard pass/fail conditions. The fiber is imaged as a dark circle while the center of the interference rings indicates the center of the connector surface.
![]() Click to Enlarge Figure 2: Diagram illustrating linear apex offset in a single axis. ![]() Click to Enlarge Figure 1: Diagram illustrating fiber height measurement methods Single-Fiber Measurement DefinitionsRadius of Curvature Fiber Height Apex Offset Polish Angle (APC or Flat-Polish Connector Only) Key Error (APC Connector Only)
![]() Click to Enlarge Figure 3: Diagram illustrating the fit planes for determining minus coplanarity for a 12-fiber multi-fiber connector. ![]() Click to Enlarge Figure 4: Schematic illustrating core dip measurement for a single fiber. Multi-Fiber Measurement DefinitionsFerrule Radius of Curvature Fiber Radius of Curvature Fiber Height Adjacent Height Differential End Face Angle Minus Coplanarity Core Dip Core dip is measured by fitting an ideal paraboloid to the curvature of the region of interest. A plane is then found that passes through points on this paraboloid at a specified radius away from the fiber center (15 µm for IEC industry standards). The core dip is the difference between the height on the plane at coordinates matching the position of the fiber center and the height of the lowest point on the fitted paraboloid. Figure 4 illustrates how to determine both the low point and the theoretical fiber height. Geometry Limit The GL16 Fiber End Face Interferometer features a measurement software program that is fully integrated into the system. The intuitive controls and customization options ensure that it is easy to use right out of the box while also providing sufficient flexibility to accommodate any user requirements during the measurement process. The GL16 interferometer is equipped with both local and remote system operation. Locally, the system can be controlled via the touch-screen display or using a keyboard or mouse peripheral via the USB 3.0 port located at the rear of the system. Remote control of the system can be accomplished by connecting the interferometer to a network via the Ethernet port located at the rear of the system and then accessing the controls via an easy-to-use browser application. Measurement data in the form of .CSV or PDF format can be accessed and copied using the remote control functionality.
Multi-Fiber Software FeaturesWhen used with a multi-fiber connector, such as an MT-style ferrule or MPO-style connector, the software tailors the user interface, measurement parameters, and field of view to accommodate these connectors. The GL16 interferometer includes scan setup profiles for MPO-style connectors by default. Additionally, users can create new profiles and parameter rulesets to accommodate other connectors via the scan setup dialog. The images below show screenshots of the software when scanning a 12-fiber ferrule using an IEC standard ruleset. ![]() Click to Enlarge Scan Control Screen Displays main scan controls, live sample image, and the result of the last scan performed. When the system is first initialized, a live view image is not shown. An on/off switch allows the bright LED source to be turned off when not in use. ![]() Click to Enlarge Live View This live image from an MT12 connector is displayed on the scan control screen (left image). The outer diameters of the 12 fibers mounted in the connector are visible in the scan. The red button in the lower right of the image is used to focus the view. ![]() Click to Enlarge Scan Result Displays the pass/fail limits of the scanned parameters, the measured result, and the pass/fail result for each fiber in the multi-fiber connector. The report can be exported to a printable scan report; click here for a sample. ![]() Click to Enlarge 3D Scan Result Displays the 3D image based on the results of the interferometric scan.
Single-Fiber ElementsThe GL16 interferometer can handle both multi-fiber and single-fiber connector types. When switching connector mounts, Thorlabs recommends performing a mount calibration using either the included calibration ferrule (multi-fiber connectors) or leveling tool (single-fiber connectors) and following the instructions on the calibration screen. ![]() Click to Enlarge Calibration Screen Displays the calibration options available for magnification, tilt stage, and four types of connector mounts. ![]() Click to Enlarge Live View and Scan Control Displays main scan controls, live sample image, and the live scan image from the sample. The outer diameters of the 12 fibers mounted in the connector are visible in the scan. The red button in the lower right of the image is used to focus the view. ![]() Click to Enlarge Scan Result Displays the pass/fail limits of the scanned parameters, the measured result, and the pass/fail result for each parameter. The report can be exported to a printable scan report; click here for a sample. ![]() Click to Enlarge 3D Scan Result Displays the 3D image based on the results of the interferometric scan. Data ManagementResults from a scan, including all physical parameters, are stored in an internal SQL database. At the end of a successful scan, the result logs show the pass/fail status of each connector scanned and the cause(s) of a failed device. Further detail such as 3D scan images and a report of all measured parameters is available for each device scanned. All scan data reports can be exported in CSV file format as well as a PDF-format and can be viewed locally or through remote access. Exported measurements can be stored offline after downloading them via remote access. ![]() Click to Enlarge Result Logs Displays all previously performed scans. Each result can be opened to view detailed results such as parameter values and 3D images. ![]() Click to Enlarge CSV Export Tests selected in the Result Logs can have their results and scan parameters exported to CSV format for easy viewing using a spreadsheet program. Figure 1: At left is shown a
Reading Fiber Optic InterferogramsInspection interferometers split light from a source between a reference flat and a surface under test. By recombining the beams of the reference arm and sample arm, an interference pattern is created allowing imperfections in a fiber tip to be inspected without making physical contact. When produced perfectly, fibers are polished to match the height, curvature, and angle of their ferrule tip. With no imperfections, the fiber end face will seamlessly match the rest of the ferrule tip. This interferogram will be a bullseye of alternating constructive and destructive interference, or fringes (Figure 1). The location of the fiber end is marked in green on the fiber schematics and circled in green on the interferograms. Note that the fiber is not perfectly centered in the ferrule. There will be a small offset between the fiber center and the apex of polish; often, an off-center fiber can make disturbances in the interferogram easier to see, as the fiber interacts with more fringes. Deviations from an ideal polish will result in visible distortions within the green-circled region of the interferogram. If a fiber end protrudes past the surface of the ferrule, the interferogram will show a distortion that advances the fringe pattern away from the ferrule's apex of curvature (Figure 2). If a fiber end is undercut, the interferogram will show a distortion with retreats from the apex of curvature (Figure 3). An undercut fiber could collect dust, which will either absorb or scatter light, causing dots to appear in the interferogram (Figure 4). If a fiber end has shattered in the polishing process, the interferogram will be highly irregular (Figure 5). Figure 2: At left is shown a
Figure 3: At left is shown a
Figure 5: At left is shown a
Figure 4: At left is shown a
![]() Components Included
Optional Purchases (Available Below)
The GL16 Interferometer provides all the necessary components for fiber end face geometry measurement integrated into a compact housing with a 7" capacitive touch-screen display for local control. The intuitive software user interface is designed for ease of use while providing a high degree of customizability over testing and report export options. One GL16M4 Mounting Fixture is included; other fixtures can be purchased separately below. Each mounting fixture includes two knurled thumbscrews that are used to attach it to the sample port directly below the display. The sample port has a controllable, motorized stage that tilts to adjust for connectors with a 0° or 8° polish. Use the appropriate fixture insert (sold separately below) for the angled connector and perform a mount calibration when switching to a new mount. ![]() ![]() Click to Enlarge Single Mode FC/PC Patch Cable Mounted to GL16 Interferometer
Thorlabs' single-fiber mounting fixtures use an integral leaf spring design to provide accurate and repeatable mounting of fiber patch cables in the GL16 interferometer. The GL16S2 fixture is compatible with Ø2.5 mm ferrules, as well as FC/PC, SC/PC, and ST/PC connectors. A GL16L2 Leveling Tool is required for calibration when changing mounting fixtures. The GL16A1 and GL16A4 Fixture Inserts provide compatibility with 2.0 mm narrow key (Type R) and 2.2 mm wide key (Type N) FC/APC connectors, respectively. For compatibility with SC/APC connectors, use the GL16A3 Fixture Insert. Custom mounts are also available upon request by contacting Tech Support. The mounting fixture attaches to the tilt stage with two knurled thumbscrews. To mount a connector, first turn the locking lever to the left to open it, insert the connector into the mount until it bottoms out, and then turn the lever to the right to lock the connector in place. When mounting ferrules with an angled polish, such as FC/APC or SC/APC connectors, secure the appropriate fixture insert on the mounting fixture using a 0.05" hex key. ![]()
Thorlabs' single-fiber mounting fixtures use an integral leaf spring design to provide accurate and repeatable mounting of fiber patch cables in the GL16 interferometer. The GL16S1 fixture is compatible with Ø1.25 mm ferrules and LC/PC connectors. A GL16L1 Leveling Tool is required for calibration when changing mounting fixtures. The GL16A2 Fixture Insert provides compatibility with LC/APC connectors by aligning the angled polish of these ferrules with the interferometer. Custom mounts are also available upon request by contacting Tech Support. The mounting fixture attaches to the tilt stage with two knurled thumbscrews. To mount a connector, first turn the locking lever to the left to open it, insert the connector into the mount until it bottoms out, and then turn the lever to the right to lock the connector in place. When mounting ferrules with an angled polish, such as LC/APC connectors, use the GL16A2 Fixture Insert. ![]() ![]() Click to Enlarge GL16M1 Mounting Fixture on GL16 Interferometer
These True Angle Connector Mounting Fixtures use high-accuracy guide pins machined into a precision aperture plate to hold the connectors in alignment during the interferometer scan. By using the plane perpendicular to center lines of the connector guide holes as a reference flat, very accurate measurements of the connector surface are possible. Four mounting fixture options are available: we offer a 12-fiber row and 16-fiber row MT-style ferrule mounts and 12-fiber and 16-fiber row MPO-style fixtures. The MPO-style fixtures can also be used with MTP connectors. To insert the connector, slide it into the mount onto the guide pins using a motion similar to when two multi-fiber connectors are mated in a bulkhead or mating sleeve. Aperture plates with guide holes for mounting connectors with pins are available upon request; please contact Tech Support with inquiries. | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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