Also known as the Faraday Rotator mirror, a Faraday mirror is manufactured by combining a Faraday rotator with a mirror. The rotator is for 45-degree rotation.
In this component, light hitting the reflector device first passes through the Faraday rotator, then reflects at the mirror, and finally passes the Faraday rotator a second time. It is known as double-pass configuration, which is very important for certain applications.
Faraday mirrors with fiber optic pigtail
The Faraday mirrors with a Fiber Optic Pigtail are designed in a way that returns light with a 90-degree orthogonal polarization relative to the input state of polarization or SOP. It’s said that pigtail-style Faraday mirrors allow greater control over the design of systems, which include fiber sensors, erbium-doped fiber amplifiers, and tunable fiber lasers. Ideally, the Faraday mirrors are used in fiber interferometers as they provide a high signal-to-noise ratio.
Use of Faraday mirrors for fiber interferometers
In simple words, the Faraday mirrors with a fiber optic pigtail improve the performance of fiber interferometers. Other than this, the device is used in fiber amplifiers and fiber lasers.
Any state of polarization perturbations to the polarization state caused by the fiber are reversed during the return trip when a Faraday mirror is placed at the end of a length of single-mode fiber. Here, the return polarization is rotated to be 90 degrees orthogonal to the input polarization.
This is an important element in a fiber interferometer, especially where undesired changes in polarization must be controlled for successful interference.
Frequently asked questions related to Faraday mirrors
Why do Faraday mirrors come in different sizes? Is there any specific rule to use different-sized Faraday mirrors?
For each wavelength of Faraday mirrors, different rotator materials are used. The Faraday mirrors are available in different sizes because the materials used have different magnetic field requirements and different rotation values per unit length.
So, before you invest in this component, check the detailed description of the material used and the design issues involved. Also, choose as per your requirements.
Are there Faraday mirrors for wavelengths shorter than 1300 nm?
There are no Faraday mirrors for wavelengths shorter than 1300nm. It’s because the Faraday rotators are too long to allow low-loss coupling in mirror configurations. This can only be customized as per your requirements, but the losses will be high.
Another option is to combine polarization-maintaining fiber-pigtailed Faraday rotators with fiber reflectors. You might achieve the same result with this combination.
Conclusion
Faraday mirrors with a fiber optic pigtail play a major role in different applications, especially fiber interferometers. The only thing is what type of mirror you use and how you use it. You should be very cautious before investing in this component.
In the industry, you will find many standards and customized manufacturers of Faraday mirrors as well as a combination of the two. You just need to know your requirements before connecting with a manufacturer.
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