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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Classification, Effect, Working Principle and Characters of Optical Isolator

Optical Isolator is an optical passive device that only allows passing through of one-way light, whose effect is to limit direction of light and keep light transports in a single direction. Thus, via fiber optic cables echo reflected light can be isolated by Optical Isolator to improve optical transmission efficiency. This article, I will focus on classification, working principle and features of Optical Isolator.

For the purpose of satisfying demand of different fields, Optical Isolator Manufacturer produced various kinds of Optical Isolator, mainly include: In-Line Isolator, Free Space Isolator and Fiber Optical Isolator and so on. It is widely used in optical fiber amplifier, fiber laser, fiber CATV net and satellite communication and so many fields. Generally speaking, wavelength of Optical Isolator is from 800nm to 1300nm, of course, there are some exceptions.
Now let's have a look at working principle of free space isolator: magneto-optical crystal Faraday Effect. As shown in the following, forward incoming signal light turns to linearly polarized light through polarizer. Faraday rotation magnetic media and external magnetic field make signal light have a 45 degree rotation at right. To backlight, when linearly polarized light pass through place media, its direction also have a 45 degree turning at right, thus, make polarization direction of backlight cross-cut with polarizer to completely block the transportation of reflected light.
Besides, follow me to effect of Optical Isolator. That is to prevent all bad influences on light source and light system caused by after transmission light. For example, install an Optical Isolator between diode laser source and light transmission system can decrease bad effect that reflected light have on stability of spectra of the light output power. At the same time, in the system of high speed direct modulation and direct detection of optical fiber communication, backward transmission light will produce extra noise which can make the system performance degradation. At this time, Optical Isolator is needed to remove the noise. Apart from these, installation of in-line isolator at both sides of fiber amplifier can improve working stability of fiber amplifier.
The most important thing is the characters of Optical Isolator. Due to its high isolation, low insertion loss, high reliability, high stability, extremely low polarization loss and polarization mode dispersion, it is widely accepted by customers all over the world. That's why so many Optical Isolator Manufacturers are flooding into the international market to challenge the fierce competition and manage to make their product a good selling point.
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