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 often created for lighting or decoration including Optical Fiber Proof-Testing Machine. They are also used on short range communication applications like on vehicles and ships. As a result of plastic optical fiber’s high attenuation, they have got restricted information carrying bandwidth.
Whenever we talk about fiber optic networks and fiber optic telecommunications, we actually mean glass optical fibers. Glass optical fibers are mostly created from fused silica (90% at the very least). Other glass materials including fluorozirconate and fluoroaluminate are also utilized in some specialty fibers.
2. Glass optical fiber manufacturing process
Before we start talking the best way to manufacture glass optical fibers, let’s first take a look at its cross section structure. Optical fiber cross section is actually a circular structure composed of three layers inside out.
A. The inner 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 center layer is referred to as the cladding. It offers 1% lower refractive index compared to the core material. This difference plays an essential part overall internal reflection phenomenon. The cladding’s diameter is generally 125um.
C. The outer layer is called the coating. It is in reality epoxy cured by ultraviolet light. This layer provides mechanical protection for that fiber and helps make the fiber flexible for handling. Without this coating layer, the fiber will be really fragile and easy to break.
Because of optical fiber’s extreme tiny size, it is not practical to create it in a single step. Three steps are required since we explain below.
1. Preparing the fiber preform
Standard optical fibers are made by first constructing a sizable-diameter preform, using a carefully controlled refractive index profile. Only several countries including US are able to make large volume, good quality Optical Fiber Ribbon Machine preforms.
The process to help make glass preform is referred to as 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 is then injected in to the hollow tube.
As the lathe turns, a hydrogen burner torch is moved up and down the away from the tube. The gases are heated up by the torch as much as 1900 kelvins. This extreme heat causes two chemical reactions to happen.
A. The silicon and germanium interact with oxygen, forming silicon dioxide (SiO2) and germanium dioxide (GeO2).
B. The silicon dioxide and germanium dioxide deposit on the inside the tube and fuse together to create glass.
The hydrogen burner will be traversed up and down the size of the tube to deposit the material evenly. Right after the torch has reached the conclusion from the tube, this will make it brought back to the start of the tube and also the deposited particles are then melted to form a solid layer. This procedure is repeated until a sufficient amount of material has become deposited.
2. Drawing fibers on the drawing tower.
The preform will be mounted for the top of the vertical fiber drawing tower. The preforms is first lowered right 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 several buffer coating cups and UV light curing ovens, finally onto a motor controlled cylindrical fiber spool. The motor slowly draws the fiber through the heated preform. The ltxsmu fiber diameter is precisely controlled with a laser micrometer. The running speed in the fiber drawing motor is all about 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 good 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 Secondary Coating Line core, cladding and coating sizes
A. Refractive index profile: By far the most critical optical spec for fiber’s information carrying bandwidth
B. Attenuation: Very critical for long distance fiber optic links
C. Chromatic dispersion: Becomes increasingly more critical in high speed fiber optic telecommunication applications.