There are two major varieties of optical fibers: plastic optical fibers (POF) and glass optical fibers – so how are optical fibers made?
1. Materials for optical fibers
Plastic optical fibers are often made for lighting or decoration including Optical Fiber Coloring Machine. Also, they are applied to short range communication applications including on vehicles and ships. Due to plastic optical fiber’s high attenuation, they have very limited information carrying bandwidth.
Whenever we speak about fiber optic networks and fiber optic telecommunications, we actually mean glass optical fibers. Glass optical fibers are mostly made from fused silica (90% a minimum of). Other glass materials like fluorozirconate and fluoroaluminate are also found in some specialty fibers.
2. Glass optical fiber manufacturing process
Before we start talking how to manufacture glass optical fibers, let’s first have a look at its cross section structure. Optical fiber cross section is a circular structure composed of three layers inside out.
A. The interior layer is known as the core. This layer guides the light and prevent light from escaping out by a phenomenon called total internal reflection. The core’s diameter is 9um for single mode fibers and 50um or 62.5um for multimode fibers.
B. The middle layer is referred to as the cladding. It provides 1% lower refractive index compared to the core material. This difference plays a vital part altogether internal reflection phenomenon. The cladding’s diameter is usually 125um.
C. The outer layer is called the coating. It is actually epoxy cured by ultraviolet light. This layer provides mechanical protection for that fiber and definitely makes the fiber flexible for handling. Without this coating layer, the fiber can be really fragile as well as simple to break.
Due to optical fiber’s extreme tiny size, it is far from practical to generate it in a single step. Three steps are needed since we explain below.
1. Preparing the fiber preform
Standard optical fibers are made by first constructing a sizable-diameter preform, with a carefully controlled refractive index profile. Only several countries including US have the ability to make large volume, high quality SZ Stranding Line preforms.
The process to make glass preform is called MOCVD (modified chemical vapor deposition).
In MCVD, a 40cm long hollow quartz tube is fixed horizontally and rotated slowly over a special lathe. Oxygen is bubbled through solutions of silicon chloride (SiCl4), germanium chloride (GeCl4) and other chemicals. This precisely mixed gas will then be injected to the hollow tube.
Since the lathe turns, a hydrogen burner torch is moved up and down the outside of the tube. The gases are heated up from the torch as much as 1900 kelvins. This extreme heat causes two chemical reactions to occur.
A. The silicon and germanium react with oxygen, forming silicon dioxide (SiO2) and germanium dioxide (GeO2).
B. The silicon dioxide and germanium dioxide deposit on the within the tube and fuse together to make glass.
The hydrogen burner will then be traversed up and down the duration of the tube to deposit the fabric evenly. Right after the torch has reached the final from the tube, it is then brought back to the starting of the tube as well as the deposited particles are then melted to create a solid layer. This procedure is repeated until a sufficient level of material continues to be deposited.
2. Drawing fibers over a drawing tower.
The preform is then mounted towards the top of a vertical fiber drawing tower. The preforms is first lowered into a 2000 degrees Celsius furnace. Its tip gets melted until a molten glob falls down by gravity. The glob cools and forms a thread since it drops down.
This starting strand will be pulled through a series of buffer coating cups and UV light curing ovens, finally onto a motor controlled cylindrical fiber spool. The motor slowly draws the fiber from your heated preform. The ltxsmu fiber diameter is precisely controlled by way of a laser micrometer. The running speed in the fiber drawing motor is approximately 15 meters/second. As much as 20km of continuous fibers can be wound onto just one spool.
3. Testing finished optical fibers
Telecommunication applications require very high quality glass optical fibers. The fiber’s mechanical and optical properties are then checked.
A. Tensile strength: Fiber must withstand 100,000 (lb/square inch) tension
B. Fiber geometry: Checks Optical Fiber Coloring Machine core, cladding and coating sizes
A. Refractive index profile: Probably the most critical optical spec for fiber’s information carrying bandwidth
B. Attenuation: Very crucial for long distance fiber optic links
C. Chromatic dispersion: Becomes a lot more critical in high speed fiber optic telecommunication applications.