The two main major types 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 usually made for lighting or decoration like Optical Fiber Ribbon Machine. Also, they are utilized on short range communication applications including on vehicles and ships. Due to plastic optical fiber’s high attenuation, they may have restricted information carrying bandwidth.
Once we speak about fiber optic networks and fiber optic telecommunications, we actually mean glass optical fibers. Glass optical fibers are mainly made from fused silica (90% at least). Other glass materials including fluorozirconate and fluoroaluminate will also be used 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 inner layer is known as the core. This layer guides the light and stop 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 center layer is referred to as the cladding. It provides 1% lower refractive index than the core material. This difference plays a crucial part overall internal reflection phenomenon. The cladding’s diameter is generally 125um.
C. The outer layer is referred to as the coating. It really is 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 and easy to break.
Because of optical fiber’s extreme tiny size, it is really not practical to produce it in a single step. Three steps are essential while we explain below.
1. Preparing the fiber preform
Standard optical fibers are made by first constructing a sizable-diameter preform, having a carefully controlled refractive index profile. Only several countries including US have the capacity to make large volume, high quality Fiber Drawing Machine preforms.
The process to create glass preform is called MOCVD (modified chemical vapor deposition).
In MCVD, a 40cm long hollow quartz tube is fixed horizontally and rotated slowly on the special lathe. Oxygen is bubbled through solutions of silicon chloride (SiCl4), germanium chloride (GeCl4) and/or 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 the tube. The gases are heated up from the torch up to 1900 kelvins. This extreme heat causes two chemical reactions to happen.
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 be traversed up and down the length of the tube to deposit the fabric evenly. After the torch has reached the final in the tube, it is then brought back to the beginning of the tube and also the deposited particles are then melted to form a solid layer. This method is repeated until a sufficient amount of material has become deposited.
2. Drawing fibers on a drawing tower.
The preform will then be mounted for the top of the 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 is then pulled through a number 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 of the fiber drawing motor is about 15 meters/second. As much as 20km of continuous fibers can be wound onto a single 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 more and more critical in high-speed fiber optic telecommunication applications.