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Faraday Mirrors with Fiber Optic Pigtail


  • Returns Light at 90° Orthogonal Polarization Relative to Input
  • Bismuth Iron Garnet (BIG) Faraday Rotating Element
  • 1310 nm and 1550 nm Design Wavelengths
  • Unterminated, FC/PC, or FC/APC Versions Available

MFI-1310-APC

Faraday Rotator
(Magnet, Film)

Planar
Mirror

Lens

Internal Schematic

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Click to Enlarge
Schematic illustrating polarization rotation as light passes through the Faraday rotating element from the fiber input (top) and after reflecting off the mirror (bottom).

Features

  • Returns Light with Polarization Rotated 90° Relative to Input
  • Bismuth Iron Garnet (BIG) Faraday Rotating Element
  • 1310 nm or 1550 nm Center Wavelengths Available
  • Available with 2.0 mm Narrow Key FC/PC or FC/APC Connectors or Unterminated Leads

Thorlabs' Faraday Mirrors with a Fiber Optic Pigtail are designed to return light with a 90° orthogonal polarization relative to the input state of polarization (SOP). They allow for greater control over the design of systems such as fiber sensors, erbium-doped fiber amplifiers, and tunable fiber lasers. Faraday mirrors are available with center wavelengths of 1310 nm or 1550 nm. With <0.8 dB insertion loss and >50 dB return loss, these devices provide a high signal-to-noise ratio, which makes them ideal for use in fiber interferometers (see the Applications tab).

Rotation of the polarization state is achieved by passing light through a Faraday rotator (shown in the diagram to the right), which consists of a film of bismuth iron garnet (BIG) that has an external magnetic field applied to it by rare-earth magnets. A single pass through the Faraday rotator causes the polarization state of light to rotate by 45° ± 1°. A planar mirror placed after the Faraday rotator returns light back at the same angle of incidence; light passes through the Faraday rotator a second time and light re-entering the input fiber has a polarization state rotated 90°, or orthogonal, to the input polarization state. 

Faraday mirrors additionally provide the ability to minimize alterations to the polarization state induced by thermal and mechanical perturbations in the fiber. This behavior is possible because the light will travel through the same fiber when entering and exiting the Faraday rotator (i.e., the pigtailed single mode fiber). Any perturbations to the polarization state that are caused by the fiber are reversed during the return trip. As such, Faraday rotator mirrors will correctly compensate for SOP changes caused by the fiber without using polarization-maintaining fiber; however, the return polarization will be orthogonal to the input polarization. 

These Faraday Rotator Mirrors are pigtailed with 1 m of SMF-28 Ultra single mode fiber, which is mounted in a standard Ø900 µm tight tube buffer with proper strain relief. Versions are available with 2.0 mm narrow key FC/PC or FC/APC connectors; the 1550 nm Faraday rotator is also available unterminated.

Custom models are also available upon request. Contact Thorlabs' Tech Support for more information.

Faraday Rotating Mirror Diagram 2
Click to Enlarge
Figure 1: Fiber-based interferometer using Faraday rotators to eliminate unwanted polarization effects.

Applications

Faraday rotators are useful for improving the performance of fiber interferometers, as well as fiber amplifiers and fiber lasers. When a Faraday rotator is placed at the end of a length of single mode fiber, any state of polarization (SOP) perturbations to the polarization state that are caused by the fiber are reversed during the return trip; however, the return polarization is rotated to be 90° orthogonal to the input polarization. This is especially useful in a fiber interferometer, where undesired changes in polarization must be controlled for successful interference. Figure 1 shows an example fiber interferometer setup which uses Faraday mirrors to neutralize undesired polarization effects.

Alternatively, as shown in Figure 2, when light passes through a length of fiber, such as an erbium-doped fiber amplifier, and is reflected by the Faraday mirror, the returning beam has a polarization direction orthogonal to that of the input beam. A polarizer can then be used to separate out the counterpropogating beams. This same principle can also be applied to a fiber laser, as shown in Figure 3.

Faraday Rotating Mirror Diagram 1
Click to Enlarge
Figure 2: Fiber-based amplifier using a Faraday rotator to create an input and output beam with orthogonal SOPs.
Faraday Rotating Mirror Diagram 3
Click to Enlarge
Figure 3: Fiber laser using a Faraday rotator to create an input and output beam with orthogonal SOPs.

Posted Comments:
yujun.deng  (posted 2014-09-24 17:18:04.853)
I wonder whether you could have Faraday Mirrors with Fiber Optic Pigtail at 1064 nm.
jlow  (posted 2014-09-25 03:32:37.0)
Response from Jeremy at Thorlabs: We can build this. I will contact you directly to get the requirements for your application and quote this.
Greg  (posted 2009-03-03 12:01:33.0)
A response from Greg at Thorlabs to yfeng: Thank you for your interest in Thorlabs products. We are able to make custom Inline Faraday Rotator Mirrors. A member of our Technical Support team will be in contact with you shortly.
yfeng  (posted 2009-03-03 06:50:48.0)
Hi, Do you offer Faraday rotator mirrors at 1180nm with similar specs? Best Regards, Yan Feng

Faraday Mirrors with Fiber Pigtail for 1310 nm

Item # Center
Wavelength
Bandwidth Insertion
Lossa,b
Return
Lossa,c
Faraday
Rotationa,d
Max Power
Level
Fiber Pigtail Termination
MFI-1310-FC 1310 nm 12 nm 0.5 dB (Typ.)
0.8 dB (Max)
>55 dB 45° ± 1° <300 mW 1 m of SMF-28 Ultra FC/PC
MFI-1310-APC FC/APC
  • Values are specified without connectors.
  • Insertion loss is defined as total optical loss after return trip (second pass).
  • Return loss is defined as signal reflected by components other than the mirror.
  • Faraday rotation is specified for a single pass.
Based on your currency / country selection, your order will ship from Newton, New Jersey  
+1 Qty Docs Part Number - Universal Price Available / Ships
MFI-1310-FC Support Documentation
MFI-1310-FCInline Faraday Rotator Mirror for 1310 nm, FC/PC Connector
$530.40
Today
MFI-1310-APC Support Documentation
MFI-1310-APCInline Faraday Rotator Mirror for 1310 nm, FC/APC Connector
$541.62
Today

Faraday Mirrors with Fiber Pigtail for 1550 nm

Item # Center
Wavelength
Bandwidth Insertion
Lossa,b
Return
Lossa,c
Faraday
Rotationa,d
Max Power
Level
Fiber Pigtail Termination
MFI-1550 1550 nm 17 nm 0.5 dB (Typ.)
0.8 dB (Max)
>55 dB 45° ± 1° <3 W 1 m of SMF-28 Ultra No Connectors
MFI-1550-FC <300 mW FC/PC
MFI-1550-APC FC/APC
  • Values are specified without connectors.
  • Insertion loss is defined as total optical loss after return trip (second pass).
  • Return loss is defined as signal reflected by components other than the mirror.
  • Faraday rotation is specified for a single pass.
Based on your currency / country selection, your order will ship from Newton, New Jersey  
+1 Qty Docs Part Number - Universal Price Available / Ships
MFI-1550 Support Documentation
MFI-1550Inline Faraday Rotator Mirror for 1550 nm, No Connector
$520.20
Today
MFI-1550-FC Support Documentation
MFI-1550-FCInline Faraday Rotator Mirror for 1550 nm, FC/PC Connector
$530.40
Today
MFI-1550-APC Support Documentation
MFI-1550-APCInline Faraday Rotator Mirror for 1550 nm, FC/APC Connector
$541.62
Today
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