Fiber optics is about technology in optical fibers, the most flexible type of waveguide for light propagation. Fiber core technologies are described in Fiber Optics, including various types of glass fibers (eg, silica fibers and fluoride fibers), as well as plastic fibers. In addition to different materials, fibers differ in many other aspects, especially the propagation characteristics in the fiber core. E.g:
Single-mode fiber and multi-mode fiber, support one guided wave mode or multiple modes, large mode area fiber with large effective mode area.
PM Fiber
Low-loss fiber for long-distance data transmission
Dispersion graded fibers and dispersion shifted fibers with improved dispersion properties
Rare earth doped fibers are used in fiber amplifiers and lasers, sometimes in the form of double-clad fibers operating at high powers, high nonlinear fibers, e.g. for supercontinuum light generation, hollow-core fibers, where part of the light is in air There are also various special fibers that are propagated. Some are photonic crystal fibers (or microstructured fibers) that contain small air holes in the fiber core.
Light enters the fiber and travels in the fiber with a fixed beam radius until it exits the fiber. Multiple optics can be connected together. In an all-fiber device, the light may be completely distributed in the waveguide structure.
optic fibre cable
Optical fibers are usually applied in the form of fiber optic cables, where the optical fiber is placed in a support structure to protect it from mechanical stress and liquids. The ports of fiber optic cables usually use fiber optic connectors, which can be easily connected to another cable, although fiber optic connectors are generally fragile.
The differences between fiber optic cables are reflected in the following aspects:
May contain different types of optics, such as single-mode or multi-mode glass fiber or plastic fiber, and have different specifications.
Cables may contain varying numbers of fibers, from one to several hundred.
Optical fibers are protected to varying degrees, eg, against mechanical damage and against moisture.
Some fibers are fireproof.
Fiber Optic Devices
In addition to optical fibers, there are many kinds of optical fiber devices, which can be connected by optical fibers. Many fiber optic devices are fabricated from optical fibers, while others may contain various other materials, but are coupled via optical fibers, ie, optical fibers as input and output ports. Some examples of fiber optic devices include:
Fiber-coupled laser diodes can be used as light sources for fiber optics. It is also possible to use solid state bulk lasers or other lasers in combination with a fiber coupling device.
Optical fiber couplers are used to combine the light bundles of different light sources into optical fibers, or as fiber splitters, such as distributing TV signals to different users' homes.
Fiber-optic mode size converters can efficiently couple light between fibers with different effective mode areas.
Fiber Bragg gratings can be used as wavelength-selective fiber-optic reflectors, such as add-drop multiplexers for wavelength-division multiplexing systems in communications applications. Another application is the introduction of wavelength-dependent losses, eg, for gain flattening in fiber amplifier systems.
Fiber optic connectors allow removable or reconfigurable connections between fiber optic devices, similar to electrical connectors, but more sensitive.
A fiber collimator connects fiber optics with free-space optics: it collimates light output from an optical fiber, or directs a collimated beam into an optical fiber.
Fiber-coupled Faraday isolators, rotators, and circulators can manipulate the polarization state of the beam.
There are many other types of fiber-coupled devices used for beam steering, such as fiber-optic modulators and saturable absorbers.
There are also fiber-coupled power meters and spectrometers that measure optical power and spectrum. There are also devices that measure polarization states.
Fiber Optics
Multiple fiber optics can be combined into an all-fiber device with complex functions. For example, by assembling fiber-coupled laser diodes, rare-earth-doped fibers, and fiber couplers into diode-pumped fiber lasers. Additional devices such as fiber-coupled saturable absorbers and fibers for dispersion compensation enable mode-locked operation, in which the laser radiates a train of ultrashort pulses. Devices can also be added for Q-switching, power stabilization, wavelength tuning and other functions.
