Polarization Maintaining Fiber Coupler: A Basic High Precision Fiber Sensor Component

By Author: Ryan
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A crucial element in achieving the coupling, splitting, and multiplexing of linearly polarized light is the polarization maintaining coupler. Due to its ability to transmit two orthogonal linearly polarized lights steadily while maintaining their respective polarization states, it is becoming an essential optical component for a variety of military interference sensors, coherent optical communications, fiber optic hydrophones, and gyroscopes, among other applications.


Challenges in producing fiber couplers that keep polarization


The main component of these optical fiber sensors is the optical fiber coupler, and the performance of this component greatly affects the optical fiber sensor's total performance.


The method of laser interferometry involves striking the polarization-maintaining fiber with a helium-neon laser from the side, rotating the two fibers independently, and identifying the direction of the fiber's polarization axis by observing the shift in interference fringes as the two fibers ...
... spin. Using this technique, the fiber is sandwiched between two orthogonally positioned polarizers, and the birefringence produced by the stress application portion is used to identify the fiber's polarization axis.


The two polarization-maintaining fibers must be brought close together in parallel, fixed, and then drawn after determining their respective polarization axes. The optical fiber will, however, rotate to stray off the polarization-maintaining axis throughout this operation. Stress may also be produced by the optical fiber's modest rotation at the same time. The device's performance will also be impacted by these elements. Thus, resolving these issues is a challenge in the production of fiber couplers that retain polarization. The polarization maintaining splitter is equally vital.


The polarization-maintaining fiber coupler's performance


Polarization-maintaining fiber couplers have the same primary performance metrics and influencing variables as single-mode fiber couplers used in communication. The coupling ratio and additional loss are two crucial metrics for assessing how well polarization-maintaining fiber couplers are working. A key aspect influencing the extra loss in the polarization-maintaining coupler is the diameter of its double cone. The flame temperature can regulate the coupling ratio.


The ratio of optical power transmitted down the polarization axis Y and the main axis X at the output port of the polarization-maintaining fiber coupler is known as the high extinction ratio. It displays the extent to which the pm fiber coupler has maintained the linear polarization of the light. Thus, fiber optic sensors like fiber optic hydrophones, fiber optic gyroscopes, and fiber optic current sensors are mostly made of polarization-maintaining fiber couplers. It is among the fundamental parts of a high-precision fiber sensor.


The importance of fiber couplers that retain polarization


The single-mode fiber is the primary component of the polarization-maintaining fiber coupler. This kind of coupler is inexpensive and has an easy-to-manufacture technique. The external disturbance's birefringence will result in zero drift of the fiber sensor and signal fading, which will make the coupler's performance unreliable.


A particular kind of polarization maintaining coupler is one composed of polarization-maintaining fiber. Apart from its usual function of combining and splitting light, an ordinary coupler also maintains the polarization state of linearly polarized light.

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