Fuctions and Classifications of Optical Isolator

Optical isolator is a kind of free space isolator. It is common optical equipment and device used in optical fiber communication system and precision optical measurement system. It is a kind of passive optical component that allows only unidirectional light goes through. Its working principle is based on the non-reciprocity of Faraday rotation. The light reflected by the optical fiber echo can achieve good isolation effect by optical isolator. So optical isolator is to allow light to one direction and block it to the opposite direction by the passive components. Its function is to limit the direction of the lights to make the lights only go to a single direction, and in this way it can improve the efficiency of light transmission. The characteristics of optical isolator are high isolation efficiency, low insertion loss, high reliability and high stability.

Let us have a look at its working principle and function. In detail its role is to prevent the back lights made in the light transmission process for a variety of reasons do harm to the light source and optical system. For example, if between the semiconductor laser light source and optical transmission system there is an optical isolator installed; this can largely reduce the bad effect that the reflected light does to the spectrum of output power stability. In the optical communication system, we install an optical isolator in every other distance; we can reduce the power loss. Therefore the optical isolator plays an important role in optical fiber communication system, optical information processing system, optical fiber sensing and precision optical measurement.
There are a wide variety of optical isolators in the world. According to its internal structure it can be divided into block type optical isolator, fiber optical isolator and the waveguide optical isolator. There are also other kinds, such as in-line isolator and so on.
1. Block type optical isolator
This kind of isolator is a discrete component structure. It means getting together the gap of optical isolators in the light path structure through the lens of the gathered polarizer and Faraday rotator. This kind of device is relatively mature in technology, now it is commonly used in the market. The opto isolator manufacturer produces many products for the use in optical systems. However, it also has some disadvantages. It needs many optical devices, so it is relatively huge.
2. Fiber optical isolator
This type refers to do some work on the optical fiber end surface, such as polishing coating in the light path structure of isolator. It has the following characteristics. It has small size, light weight and good resistance performance to mechanical vibration. However, making the devices we should use the special optical fiber, and it requires high machining accuracy, complex producing technology and much manufacturing cost.
3. Waveguide free space isolator
Waveguide optical isolator belongs to the integrated optics. It is made on the basis of lithium niobate with Ti, and it is processed by deposition, photoetching, spreading and it is made into magneto-optic waveguide. After that it is processed together with other components. In this way we have this kind of optical isolator. It has small volume and light weight. Its thermal stability and mechanical stability are good. But due to the immature technology, its real performance still has some disparity with the required standard.
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