840 nm Fiber Isolator for Broadband SLD’s
Rev B, Sept. 14, 2018
Page 5
Chapter 4 Operation
4.1. Forward Mode
Laser light enters the isolator via the input single mode fiber. A lens collimates
the light and splits it as it goes through a birefringent beam displacer polarizer.
The light then enters the rotator, which rotates its plane of polarization 45°. It
then passes through a quartz rotator and second displacer polarizer. Finally, it
exits via another collimating lens coupling into output fiber.
4.2. Reverse Mode
Some random beam reflections will be reflected back through the fiber towards
the laser. This feedback enters the isolator and is split by the output beam
displacer. The two beams are rotated 45
by the quartz rotator and another 45
by the faraday rotator. The two beams are now oriented 90
as compared to the
forward beams and walk off a second time instead of being recombined. These
beams do not couple into the input fiber and are absorbed inside the isolator
housing. The laser is now isolated from downstream reflections.
Chapter 5 Warranty
All Thorlabs fiber
isolators are covered by Thorlabs’ six-month warranty against
defects in materials and workmanship.
WARNING
Do not attempt to disassemble the isolator.
Disassembly of the isolator voids the warranty and can be unsafe.
Please contact technical support if you have questions regarding performance or
operations. See page 10 for contact information by region.
