Features

• Polarization Control over Full Poincare Sphere
• Operates over Full Fiber Bandwidth
• Very Easy to Operate
• Compatible with Ø900 µm Jacketed Fibers

If your application includes single mode fiber and requires linearly polarized light, the FPC Series Polarization Controllers can be easily implemented to convert elliptically polarized light in a single mode fiber into another state of polarization, including linearly polarized light. This polarization conversion is achieved by loading the paddles with a prescribed number of fiber loops to create a fixed waveplate, and adjusting their positions to control the output polarization state.

These polarization controllers utilize stress-induced birefringence to create three independent fractional, fixed wave plates to alter the polarization of the transmitted light in the single mode fiber by looping the fiber around three independent spools. Each spool, in essence, represents a wave plate. See the Operation tab for more details.

The amount of birefringence induced in the fiber is a function of the fiber cladding diameter, the spool diameter (fixed), the number of fiber loops per spool, and the wavelength of the light. The fast axis of the fiber, which is in the plane of the spool, is adjusted with respect to the transmitted polarization vector by manually rotating the paddles. The FPC031, FPC032, FPC561, and FPC562 fiber polarization controllers come preloaded with fiber. All of our controllers are compatible with Ø900 µm jacketed fibers, however, the ends of the controller are capable of clamping onto Ø3 mm protective tubing.

NOTE: The FPC030 and FPC020 work well with all of our single mode fibers. For fibers with higher bend loss (e.g., Corning’s SMF-28e+), use model FPC560.
Thorlabs also offers a drop-in, clamping polarization controller, the PLC-900.

These manual polarization controllers utilize stress-induced birefringence to create three independent fractional wave plates to alter the polarization in single mode fiber that is looped around three independent spools (two for the FPC020) to create the independent fractional wave plates (fiber retarders). The amount of birefringence induced in the fiber is a function of the fiber cladding diameter, the spool diameter (fixed), the number of fiber loops per spool, and the wavelength of the light. (NOTE: the desired birefringence is induced by the loop in the fiber, not by the twisting of the fiber paddles). The fast axis of the fiber, which is in the plane of the spool, is adjusted with respect to the transmitted polarization vector by manually rotating the paddles.

To transform an arbitrary input polarization state into an arbitrary output polarization state, a combination of three paddles (a quarter-wave plate, a half-wave plate, and a quarter-wave plate) or two paddles (quarter-wave plate and a quarter-wave plate) is used. For three paddle controllers, the first quarter-wave plate would transform the input polarization state into a linear polarization state. The half wave plate would rotate the linear polarization state, and the last quarter wave plate would transform the linear state into an arbitrary polarization state. Therefore, adjusting each of the three paddles (fiber retarders) allows complete control of the output polarization state, over a broad range of wavelengths (500 – 1600 nm). Using FPC030 as an example, a plot of retardation per paddle versus wavelength is shown in Figure A for a fiber with a cladding diameter of 125 μm. The retardation, in radians, is plotted for 1, 2, and 3 loops per paddle. For fiber with a cladding diameter of 80 μm, the retardation per paddle versus wavelength is shown in Figure B.

FIGURE A: Retardation vs. Wavelength for 1, 2, and 3 Fiber Loops Per Paddle for the FPC030 Polarization Controller. The Fiber Cladding Diameter is 125 μm.

FIGURE B: Retardation vs. Wavelength for 1, 2, and 3 Fiber Loops Per Paddle for the FPC030 Polarization Controller. The Fiber Cladding Diameter is 80 μm.

The Miniature Polarization Controller utilizes stress-induced birefringence to effectively create two (2) independent fractional wave-plates which alter the polarization state in a fiber. Single mode fiber is looped into two (2) independent spools to create the independent fractional wave-plates (fiber retarders). The amount of birefringence induced in the fiber is a function of the fiber cladding diameter, the spool diameter (fixed), the number of fiber loops per spool, and the wavelength of the light. (NOTE: the desired birefringence is induced by the loop in the fiber, not by the twisting of the fiber paddles). The fast axis of the fiber, which is in the plane of the spool, is adjusted with respect to the transmitted polarization vector by manually rotating the paddles to twist the fiber.

The FPC020 can transform an arbitrary input polarization state into an arbitrary output polarization state by rotating the two paddles (two quarter-wave plates). This would allow complete control of the output polarization state over a broad range of wavelengths (480 to 1380 nm).

The retardation per paddle is a function of loop number, cladding diameter of the fiber if the loop diameter is fixed. The retardation, in radians, is plotted for 1, 2, 3, and 4 loops per paddle for a fiber with a cladding diameter of 125 μm (Figure C).

FIGURE C: Retardation vs Wavelength with Ø125 μm Cladding SMF