- Beam Splitters and Combiners
- Fiber Adapters
- Fiber Bragg Grating
- Fiber Optic Couplers
- Fiber Mirrors
- Fiber Optic Attenuators
- Fiber Patch Cords
- Fiber Probes
- Power Shutter and Safety Interlock
- Fiber Tunable Filters
- Fiber Optic Gyroscopes
- Transmitters and Receivers
- Fiber Connectors
- Fiber Alignment Structures
- Fiber Fanouts
- Fiber Coils
Frequently Asked Questions
A fiber coil is a length of optical fiber that has been wound into a coil or spiral shape. These coils can be used in a variety of applications, such as sensing, telecommunications, and laser systems, where they provide a compact and efficient way to manipulate light.
Fiber coils are typically made by winding a length of optical fiber around a mandrel or spool. The fiber is wound in a spiral shape, with each turn of the coil being separated by a small gap to prevent light from leaking between the turns. The coil can be made with a fixed pitch (i.e., the distance between each turn of the coil is constant) or with a variable pitch (i.e., the distance between each turn varies).
A variety of different types of optical fiber can be used to make fiber coils, depending on the specific application. Single-mode and multimode fibers are commonly used, as are polarization-maintaining fibers, which are designed to maintain the polarization of light as it propagates through the fiber. Specialty fibers, such as dispersion-shifted fibers and photonic crystal fibers, may also be used in certain applications.
Fiber coils have many applications in optical systems, including telecommunications, sensing, and laser systems. They can be used as polarization controllers, wavelength filters, and optical delay lines, among other things. Fiber coils are also used in fiber gyroscopes, which are used to measure rotational motion in aircraft, ships, and other vehicles.
Fiber coils can be characterized and tested using a variety of techniques. One common method is to measure the transmission spectrum of the coil using an optical spectrum analyzer or a tunable laser source. This can provide information about the coil's spectral response and the losses associated with the coil. The polarization properties of the coil can also be measured using a polarimeter or polarization analyzer. Other tests may include measuring the coil's temperature dependence, mechanical stability, and reliability under various environmental conditions.
When selecting a fiber coil, several factors should be considered, including the application requirements, the type of fiber being used, and the performance characteristics of the coil. The size, length, and pitch of the coil should be selected based on the specific application requirements. The type of fiber used should be chosen based on factors such as polarization, dispersion, and transmission wavelength. The performance characteristics of the coil, such as insertion loss, polarization crosstalk, and temperature dependence, should also be evaluated to ensure that the coil meets the required specifications for the application.
Introduction to Fiber Coils
Fiber coils are specialized forms of optical fiber that are wound up to form a coil. While glass fibers are typically delivered on spools with many turns, special fiber coils are required for some applications where a well-defined winding pattern and other specifications are necessary. Fiber coils are used in various applications, including fiber-optic gyroscopes, fiber-optic sensors, fiber-optic delay lines, and fiber polarization controllers. Let's look into wht the key applications of Fiber Coils are.
What are the key uses of Fiber Coils?
Fiber-optic gyroscopes are one of the main applications of fiber coils. In this application, the Sagnac effect is exploited in a Sagnac interferometer or a fiber ring laser, and the fiber coil is used as a fiber gyro coil. Technical specifications are critical in this application, as properties such as Shupe error can directly impact the accuracy of the made gyroscopes.
Fiber-optic sensors: There are also fiber-optic sensors using specialized fiber coils. For example, fiber-optic current sensors are suitable for measuring strong electrical DC currents based on the Faraday effect in the fiber. The magnetic field generated by the electric current causes a difference in propagation constants for light with left or right circular polarization.
Fiber-Optic Delay Lines: In other cases, fiber coils are used as fiber-optic delay lines. For example, devices for self-heterodyne linewidth measurements use fiber coils. While most requirements for this application are less critical than for use in interferometers or sensors, the fiber coils still require defined specifications.
Fiber Polarization Control: Fiber coils with only a few windings are used in fiber polarization controllers. In this application, one exploits the birefringence which is introduced by the bending.
Fiber Disk Lasers: Another type of fiber coil, made of rare-earth doped fiber, is used for a not very common type of fiber lasers called side-pumped fiber disk lasers.
What to look for when selecting a Fiber Coil
Various specifications can be relevant for fiber coils. The geometrical dimensions of the coil are defined, in particular the inner and outer radius and the coil height. Usually, there is a well-defined length of fiber (often several kilometers), and possibly also the precise number of turns per layer and the number of winding layers. Coils are made with a specified winding pattern, such as quadrupole, octupole, helical, or flanged. Sophisticated high precision coil winding machines are used for producing such coils.
Fiber coils may be produced by winding the fiber on some frame made of aluminum or plastic or without such a part (frameless, freestanding) when the coil is mechanically stabilized with some adhesive. Different types of fiber coatings can be used, which may have an influence on the possible number of turns and the mechanical stability of the bindings.
Polarization-related properties are particularly critical for application in interferometers. The sensitivity to thermal influences can also be important. One often uses polarization-maintaining fiber (PM fiber) and specifies a polarization extinction ratio. In addition, there can be specifications concerning polarization cross-talk, which can be important for application in interferometers. Both the average value and the maximum value of the polarization cross-talk can be relevant. Fibers with high quality exhibit low polarization cross-talk and a low temperature sensitivity of that quantity.
Temperature changes may introduce mechanical stress through thermal expansion, which may modify birefringence properties of the fiber. The effective mode area is also relevant, concerning coupling to other fibers or nonlinear optical effects. The bending of the fiber, which is unavoidable for such a coil, will introduce some bend losses for the transmitted light, which is usually kept at a rather low level by using fiber with a sufficiently high numerical aperture. Most relevant is the resulting total insertion loss in decibels.
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