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Specialty Optical Fiber Manufacturing
Thorlabs' ITAR-certified fiber draw facility, located at our headquarters in Newton, NJ, fabricates specialty optical fiber for a variety of applications. In addition to manufacturing our extensive catalog offerings, this facility supports the flexible tower configurations and draw schedules required for fabricating custom fibers. Our engineering team has experience with designing and fabricating fibers for academic, industrial, and government applications.
The fiber drawn here is sold bare and is also made into connectorized patch cables or incorporated into many products in our ever-growing line of photonics equipment. This fiber will be sold to laboratories all over the world and will be used for everything from optogenetics to telecommunication applications.
We are able to accomodate requests for long fiber lengths resulting from one large, continuous fiber draw. However, the amount of fiber that can be drawn into a given spool will vary by production run. Please contact Tech Support with any specialty needs not covered by our standard offering. For more information about the draw process used at Thorlabs, please see the Preform Preparation and Draw Process tabs above.
Optical fiber production begins with a glass preform. The preform must be completely free of surface contaminants in order to produce high-quality fiber. We first attach a handle to the preform to allow the technician to move it without touching the preform itself. One handle is welded onto each end of the preform using an oxygen-hydrogen torch. The thermal expansion coefficient of the handle glass matches that of the preform glass to prevent the weld from separating as the temperature changes. These handles can be reused.
The handles are chucked into a lathe, suspending the preform over an oxygen-hydrogen burner. The preform is rotated as the burner slowly translates down its length, removing all surface contaminants. This process is called firepolishing. Firepolishing takes off the outermost layer of glass leaving a clean surface behind. This clean surface ensures the resulting fiber has the highest strength possible.
Once the firepolishing is complete, one of the two handles is removed leaving a pointed "drop" end. The preform is fed far enough into the furnace that, when a high enough temperature is reached, the drop end exits the furnace and initates the draw. The handle that remains will support the preform on the tower.
Click on the Draw Process tab for information about the next steps in the draw process.
Click on the Fiber Draw Tower shown below for further details.
Optical fiber production begins with a preform. The core/clad ratio of the preform is maintained during the draw process. The resulting optical fiber has this same core/clad ratio.
The silica fiber production facility at Thorlabs uses cylindrical silica preforms. Silica is commonly used to make optical fiber because it has good transmission over a wide range of wavelengths and low absorption and scattering losses (~0.2 dB/km). Silica is also highly resistant to both mechanical and optical damage. It can withstand pulling and bending as well as amplified laser pulses.
Thorlabs manufactures optical fiber in one of two ways: drawing a preform containing a glass core and a glass clad or drawing a pure silica rod and coating the resulting fiber with an optical polymer as the cladding.
The preform is prepared for draw on the glass-working lathe. Please see the Preform Preparation tab for more information about glass working and firepolishing. The handle end is chucked, or loaded, into the top-feed unit located at the top of the tower.
The top-feed unit lowers the preform into the furnace, and the heating process begins. This inline furnace has a graphite element that surrounds, but does not touch, the preform. The graphite allows the heat to be evenly distributed around the glass cylinder. High-purity, oxygen-free Argon gas is cycled through the furnace to protect the graphite element at high temperatures.
The furnace slowly heats up the preform. As the temperature rises, the preform will start to glow. This bright orange glow is caused by the heat of the furnace and will scatter at the weld between the handle and the preform. The preform transmits light similarly to the optical fiber it will become.
Once the furnace reaches about 2000 °C, the drop end of the preform begins to fall under gravity through the hole in the bottom of the furnace. The drop end is what remains after a quartz handle has been removed after firepolishing.
A technician cuts the drop end off the glass flow and begins to pull the newly drawn fiber out of the furnace. He tapes a small weight to the end of the glass and threads it through the rest of the apparatuses along the length of the tower and into the capstan puller. This process can be seen in the photo gallery below.
The fiber travels 36 feet from the furnace to the capstan. The speed that the fiber is drawn is inversely proportional to the desired diameter of the fiber: the larger the diameter, the slower the draw speed. The fiber passes through three diameter monitors: one directly after the furnace measuring the bare fiber diameter, one after it is coated, and one after the buffer jacket is applied. These monitors are connected to the tower control system. The bare glass diameter is used to control the capstan speed and maintain the desired fiber diameter.
After coming out of the furnace, the fiber travels through a cooling chamber. Chilled water and helium gas are cycled through the 150 cm long cylinder, keeping it at an internal temperature of 12 °C. The fiber is cooled to room temperature as it passes through this chamber. Fiber needs to be at room temperature for proper coating application.
Once the fiber is thin enough, the technician cuts off the bottom portion of unusable fiber and feeds it through the coating cup. Thorlabs coats its fiber with a variety of coatings including TECS, acrylate, and polyimide. TECS is an industry-leading hard optical polymer cladding material that was developed by 3M™ and is now offered exclusively by Thorlabs. A coating layer is applied as the fiber is passed through a coating cup. The thickness of the coating is controlled by the inner diameter of the carbide dies in the coating cup.
The coating goes on the fiber wet and is hardened in the UV curing units located just below the coating cup. This coating protects the surface of the optical fiber, maintaing its intrinsic strength.
The capstan at the bottom of the fiber tower provides the pulling action that forms the fiber from the preform during the draw. After exiting the capstan, the fiber is pulled through an extruder where a Tefzel, or nylon, buffer is applied. The application of the extruded buffer can be seen in the picture to the left. A wide variety of buffer colors are available.
Mid-IR Optical Fiber Manufacturing Overview
Thorlabs' optical fiber draw facility produces and draws zirconium fluoride (ZrF4) and indium fluoride (InF3) fibers in addition to drawing silica fiber. ZrF4 and InF3 fiber feature high transmission over the 300 nm - 4.5 µm spectral range or 300 nm - 5.5 µm spectral range, respectively, with no material absorption peaks, excellent mechanical strength, and good environmental stability.
Fluoride fibers are ideal for transmission in the mid-IR wavelength range. Low attenuation in the MIR wavelength range is aided by an extremely low hydroxyl ion (OH) content. Fluoride fibers also have a lower refractive index and lower chromatic dispersion when compared to other fibers that offer transmission in the mid-IR range. Thorlabs' fluoride fibers are ideal for use in applications including mid-IR spectroscopy, fiber optic sensors, imaging, and fiber lasers.
Thorlabs' fluoride fibers are fabricated using a technique that provides world-class purity, dimensional control, and strength. The glass components are combined and melted in the controlled environment of a glove box for purity. Once the glass is melted, it is poured into the preform mold and cooled.
After preparation, the preform is loaded into the down-feed unit at the top of the tower and drawn into fiber. Fluoride glass fiber is drawn using preform techniques similar to that used for silica fibers (see the Draw Process tab for details). This technique is well developed and has proven to be very effective in controlling fiber parameters, such as fiber diameter, concentricity, and the refractive index profile. The drawing temperature range of fluoride glasses is lower than that of silica, significantly reducing the cooling time. Thus, our fluoride fiber draw tower is much shorter than our silica fiber towers. The diagram below to the right details the components on our fluoride fiber draw tower.
Thorlabs' team of mid-IR fiber researchers and engineers has many years of experience in fluoride glass research and development, production, and fiber draw. Our team is divided into two groups: one dedicated to production of catalog items and the second devoted to research and development and custom fiber manufacturing. Their knowledge and expertise, as well as flexible tower configurations and draw schedules, allow us to produce both catalog items as well as custom orders. For details on our custom fluoride fiber capabilities, please contact Tech Support.
Schematic of Our Mid IR Fiber Draw Tower
With three fiber draw towers, an in-house R&D team, and on-site metrology and testing, our ITAR-qualified fiber facility is built to accommodate the flexible tower configurations and draw schedules required for volume production on short notice. It is accustomed to the on-time fulfillment of academic, industrial, and government contracts and offers same-day shipping for patch cables with custom lengths and connectors.
We are collaborating with university customers to widen our industry-leading selection of optogenetics equipment, and we routinely accept orders for modifications of Thorlabs' catalog products.