![]() This degrades the performance of an optical isolator.įiber optic isolator includes three main parts of an input polarizer, a Faraday rotator with magnet, and an output polarizer. Double-stage isolators can be designed so that the PMD induced by the first stage is largely cancelled by the second stage. Isolators are constructed using high birefringent elements and they are very prone to PMD – typically 50 to 100 fs, especially for single-stage designs. The insertion loss should be less than 1 dB in the forward direction, and in excess of 35 dB (single-stage isolator) or 60 dB (double-stage isolator) in the reverse direction. Isolators are described by peak reverse direction attenuation and by the bandwidth for which the isolation is within 3 dB of the peak value Wavelength-dependence, especially for so-called narrowband isolators that are designed to operate in a spectral range narrower than 20nm. There are a few critical parameters that determine the performance of isolators. By contrast, light propagating in the opposite direction is blocked by the first polarizer. Light propagating in one direction passes through the second polarizer because of the Faraday rotation. The Faraday material is sandwiched between two polarizers whose axes are tilted by 45° with respect to each other. Optical isolators consist of a rod of Faraday material such as yttrium iron garnet (YIG), whose length is selected to provide 45° rotation. The rotation is in the same direction for light propagating either parallel or antiparallel to the magnetic field direction. Faraday effect governs the rotation of the polarization plane of the optical beam in a magnetic field. Most fiber optic isolators use the Faraday effect to achieve their function. Their function is to reduce the level of reflected light back into the laser diode or EDFA. Isolators are placed in output circuits of devices with a high output light level such as laser diode transmitter and EDFAs, as shown in this picture. In the following parts, fiber optic isolator’s construction, operating principle and classifications will be discussed.Ī fiber optic isolator lets light passing through in one direction with a low loss while blocking the light in the opposite direction with a high loss. Therefore, isolator is an useful and indispensable device to reduce these effects. This helps prevent laser source from unwanted feedback which will damage the laser source or arouse unexpected laser problems, such as mode hop, amplitude modulate, frequency shift and so on. As a magneto-optic device, the purpose of optical isolator is to allow light to be transmitted in only one direction. Fiber optic isolator is a passive component used for fiber optic communications.
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |