The all-optical switch is the main element in the optical communication network. As the key to realize all optical network, it has a low pumping power, high switch efficiency, fast response time characteristics, so much attention in recent years has been paid.
From the late 1980s to the present, many research groups have conducted in-depth research of all kinds of all-optical switch. All-optical switch is a very important technology, it can be applied to the field of optical communications, optical computers, optical information processing and optical data processing. Optical switch as the key components of a new generation of all-optical network, mainly used to achieve light level routing, wavelength selection, optical add-drop multiplexing and optical cross-connect and self-healing protection. Therefore, the response speed optical switch, crosstalk, insertion loss performance will directly affect the quality of optical communication. The optical networking implementation depends on the light switches, optical filter, a new generation amplifier, dense wavelength division multiplexing technology devices and technological progress.
Optical switches applications in all-optical networks in addition should have a fast response speed, low insertion loss, low channel crosstalk and polarization insensitive, should also have integration and scalability and low-cost, low-power, good thermal stability and other characteristics. All-optical switch is expected to reflect its huge potential in the following applications.
(1) The calculation speed of computer depends on the increased speed of the switching elements and chip size reduction, in which regard has encountered a bottleneck. The development of optical computer is a possible way out. Optical computers may be fast photonic switching chip and chip the outside optical interconnects constitutes. Accordingly, the optical switch is the key to the development of optical computers.
(2) Electronic communication is gradually optical fiber communication replaced in order to meet the growing demand for communication capacity. Dense Wavelength Division Multiplexing technology, optical fiber communication signal transmission to achieve all optical signal exchange also rely on electronics, limiting the improvement of optical communication rate. Therefore, all-optical communication is the key to all-optical switch.
(3) Fiber optic communication systems in the long-haul network, metropolitan area network, the access network between the optical switch required by the optical cross-connects to complete; optical switch network between users rely on the OADM. The optical cross-connect and add-drop multiplexer is constituted by an optical switch array Thus, the optical switch is the basis for all-optical switching.
From the 1970s began to study the optical bistability has more than 30 years of history. However, the study of all-optical switching is also faced with many practical problems, mainly due to three reasons.
(1) All-optical switch is based on the third-order nonlinear effect. The desired optical power of switch is too high, which often takes more than the light intensity of the signal light more than five orders of magnitude. Not like the low-power electronic switch, it can’t achieve low-power light control.
(2) Due to the strong input light caused by the strong thermal effect, particularly in the dielectric absorption peak at a wavelength switching device, the heat absorption so that the device is very unstable and difficult to achieve a cascading operation of the device.
(3) The laser beam propagation in the medium microns, the power density is not high, but the nonlinear effect limited distance required to produce nonlinear power is too difficult to compress to the transverse dimension of the beam.
Therefore, reducing the switching power is the study of all-optical switch is an important task. Subject the light through the fiber waveguide or a planar integrated optical waveguide having a wavelength order of magnitude transverse dimension, can obtain a higher light power density and a longer interaction length, thereby greatly improving the efficiency of generating nonlinear optical effects, and may lower optical power to achieve all-optical switch. Waveguide-type optical switch become the main object of study. Silicon waveguides (including optical fiber) in the communication band absorption is small, but non-linear too weak, the accumulation of available ring cavity nonlinear.