Fiber Undercut / Protrusion / Tips!
Undercut and Protrusion Polishing Support Tip:
Using material that is too aggressive for final polishing could lead to excessive undercut. The wrong final polish material could also cause excessive protrusion, leading to fiber chipping and cracking during the connector mating process.
Regardless of the connector type, most polishing sequences begin with aggressive materials, including silicon carbide, to remove epoxy and diamond lapping films for beginning and intermediate polishing. These remove both surrounding material and fiber at the same rate. The last polishing step, however, requires a less aggressive material, such as silicon dioxide, to attack only the fiber. Again, using material that is too aggressive for final polishing could lead to excessive undercutting. The wrong final polish material could also cause excessive protrusion, leading to fiber chipping and cracking during the connector mating.
Cleanliness also can affect yield. Thorough cleaning of connectors between processing steps, as well as rapid changing of polishing plates, can help reduce cross-contamination and subsequent back-reflection problems.
*End-users must take care when selecting film type, make, and particle size. Excessively aggressive films can destroy a 125μm fiber, as well as the end-face radius.
Epoxy removal is also essential to contamination-free polishing. Some epoxies can be removed more easily with specific grades of silicon-carbide polishing films. The films to use in this step depend on the epoxy type and the size of the epoxy bead mounted on the connector end face. Epoxies will have varying hardness levels; some will be tacky, some firm. Films with coarser particle sizes (20 and 30 μm) remove hard epoxies easily, while films with smaller particles (9 and 5 μm) are better suited to softer epoxies.
Importance of Controlling Undercut & Protrusion
Film - Polishing Process - Geometry - epoxy removal
Undercut
- Causes Back reflections
- Internal connector reflections can cause spurious modulations and noise Feedback
- Reflection noise is an important concern in analog video
Protrusions
- Submicron measurements of differential height by reflecting monochromatic light off a surface and combining it with light reflecting off a standard to form constructive and destructive interference patterns.
- Causes Fiber Pushback and affects long-term performance
Interferometry Helps
Submicron measurements of differential height by reflecting monochromatic light off a surface and combining it with light reflecting off a standard to form constructive and destructive interference patterns
PC Polish
Fibers meet in intimate optical contact (no air gap)
Fibers compress until ferrule contact
Fiber takes a majority of the Compressive Force
Why Use Interferometry
- Quality Control of connectors
- Inspect for scratches
- Measure light loss
- Back reflection if necessary
- Interferometry checks 3D polish geometry
- Assures consistency
- Assures long-term performance
- Detailed information = more control over the process
- Effects to consider:
- Temperature cycling
- Contact pressure
- Vibration
The basic polishing process involves these steps:
Epoxy Removal
Polishing Geometry
Final Step: (finishing the optical surface)
Assembly
*** 66P Diamond Lapping Films are designed to provide consistent high-quality surface finishes in lapping applications for hard surfaces. This product series is particularly suitable for metallography sample preparation but also finds use in lapping and superfinishing other hard materials, including ceramics, semiconductors, glass, metals, and stone. To ensure high quality and reliable performance, 66P Lapping Films are made by precision-coating tightly graded diamond particles onto a 3-mil polyester substrate.***AVAILABLE IN DISCS, SHEETS, AND ROLLS, WITH OR WITHOUT PRESSURE-SENSITIVE ADHESIVE (PSA).
EPOXY MENU for Control Process
Interferometry=Real Plus (+)
The Importance of Controlling Undercut & Protrusion is paramount to a successful control process for polishing fiber. All of our support TEAM has been working with polishing, film, cleaning, and/or interferometry since the '90s. We work closely with customers to develop, resolve, and maintain process control issues. Internal connector reflections can cause spurious modulations and noise feedback. Submicron measurements of differential height by reflecting monochromatic light off a surface and combining it with light reflecting off a standard to form constructive and destructive interference patterns.
Visit Wet/Dry Cleaning Solutions for adapter cleaning and end-face Cleaning for more product info.
or more of "My World" for more application notes
Use the MENU Above ... Email or call if you have questions.