What is Optical Circulator? скачать в хорошем качестве

What is Optical Circulator?

http://www.fiberoptics4sale.com/wordp... http://www.fiberoptics4sale.com Optical circulators have at least three ports. The function of a circulator is to transmit light from one port to the next port with minimum loss. Such as from port 1 to port 2 and from port 2 to port 3. Some circulators are designed this way so that light from port 3 can go back to port 1. But most circulators don't. Light is blocked from going back from one port to the previous port. For example, light from port 2 can only go to port 3, and cannot go back to port 1. That is why it is called circulator. So how does an optical circulator work under the hood? There are a few different designs, but the ideas are similar. Here I will explain one particular design in detail and you can go to FO4Sale.com tutorial pages to check out other designs. As shown in the top part, there are three types of components inside a circulator: Birefringent Crystal, Half-waveplate, and Faraday rotator. Also the three axis are marked as x, y, and z. Light travels in the z direction. All polarization rotations happen in the x-y plane. The top part shows the actual components inside the circulator. The bottom part shows how the light's polarization is rotated. Each circle indicates the light beam position and the arrow inside the circle indicates the polarization direction of the beam. Port 1 and 3 are located at the input side, they are separated by a certain amount at the horizontal x-axis. Let's first consider how light beam travels from port 1 to port 2. A light beam launched into port 1 is split into two beams in the vertical y-axis with orthogonal polarization states. Then they pass two half-waveplates. The top beam's polarization is rotated 45° clockwise by the top half-waveplate, and the bottom beam's polarization is rotated 45° counter-clockwise by the bottom half-waveplate. So now these two beams have the same polarization direction at 45°. Then these two beams pass the Faraday rotator. The Faraday rotator rotates the polarization of both beams 45° counter-clockwise, so now the two beams are vertically polarized along the y-axis at 90°. Now they reach the second birefringent crystal. This crystal is cut in this way so that its ordinary ray passes without any displacement, and its extraordinary ray will move a certain amount at the horizontal x axis. This second birefringent crystal's ordinary ray polarization is at the vertical y-axis, so now these two beams can pass the crystal without any change and displacement, just like a regular glass. Now these two beams pass through the second Faraday rotator, which rotates their polarization 45° counter-clockwise again. And after that, the top beam is rotated 45° counter-clockwise by the top half-waveplate, and the bottom beam is rotated 45° clockwise, so now these two beam's polarization becomes orthogonal again. The third birefringent crystal is exactly the same as the first crystal, so these two beams are combined back into one single beam and get out at port 2.