CN100437215C - Reflective magneto-optical switch - Google Patents

Abstract

Reflective type magneto-optical switch, relates to a magneto-optical switche. With three right-angle prism, polarization beam splitter and polarization rotation device; First rectangular prism input external laser, then strikes into the polarization beam splitter; polarization beam splitter output will be 2 laser beam decomposition orthogonal polarization state S-P light and the second right-angle prism external input polarization beam splitter side, will be reflected to incident light polarization rotation device; polarization rotation of the input device proximal external polarization beam splitter and the second output Right-angle prism output, and output from the left will be part of the two polarized light beam strikes into a third rectangular prism; third rectangular prism external polarization rotation of the left part of the device output, and the third in the rectangular prism Polarized light reflection to the left part of the rotating device input port, the polarization rotation device, a bouquet of polarized light to the second right-angle prism, a reflection to the polarization beam splitter merger with another a bouquet of polarized light, and in accordance with the requirements of entry output ports.

Description

Reflective magneto-optical switch

technical field

The invention relates to a magneto-optical switch, in particular to a reflective magneto-optic switch.

Background technique

With the development of optical fiber communication technology and a large number of applications of DWDM, DWDM all-optical network is becoming the main development direction of communication network. The development of all-optical networks will depend on the progress of new-generation optical switches, wavelength division multiplexers, optical attenuators, and optical amplifiers. The optical switch is one of the core components of the all-optical network, and its performance directly affects the performance of the network. Optical switches have the characteristics of large-scale integration of devices, high coupling efficiency with optical fibers, large communication bandwidth, high reliability, and mass production, and have become one of the key technologies of all-optical networks. As one of the essential key components in an all-optical network, the optical switch plays a decisive role in OXC, OADM, and protection inversion. Various performances of optical switches are important reference standards for determining the performance of OADM and OXC. With the rapid development of all-optical networks, the network has put forward higher and higher requirements on the performance of optical switches, and high-performance optical switches are attracting the attention of the optical communication industry.

Traditional optical switches have optical-electrical-optical conversion during the switching process, and their switching capacity is limited by the working speed of electronic devices, which limits the bandwidth of the entire optical communication system. All-optical switching can save the optical-electrical-optical switching process and make full use of the broadband characteristics of optical communication. All-optical switching is considered to be the most potential next-generation switching technology for future broadband communication networks. In an ideal all-optical network, all functions such as signal exchange, routing, transmission and restoration are carried out in the form of light. The all-optical switch directly outputs optical signals to different ports according to different requirements without going through the traditional optical-electrical-optical conversion method. Compared with the traditional optical switch, it saves the optical-electrical-optical conversion process, simplifies the equipment accordingly, greatly improves the reliability of the network, and provides a flexible signal routing platform. Although traditional optical-electrical-optical switching is still used in current communication systems, all-optical networks require all-optical switches instead of photoelectric conversion to complete signal routing functions and achieve high network rates and protocol transparency. All-optical switches have become the core components of large-scale optical switching systems and the key factors determining network performance, and their status and importance have become increasingly prominent.

At present, optical switches can be roughly divided into two categories: traditional mechanical optical switches and newly researched non-mechanical optical switches. The development of mechanical optical switch is the most mature, it has the advantages of low insertion loss, polarization independent and small crosstalk. The disadvantage is that the switching time is long, generally on the order of milliseconds, which is far from the required microseconds and nanoseconds; the volume is large, and some have problems such as rebound jitter and poor repeatability. Non-mechanical optical switches are generally developed by utilizing the electro-optic, acousto-optic, thermo-optic, and magneto-optical effects of materials. Compared with mechanical optical switches, they have higher switching speeds, generally reaching microseconds or even On the order of nanoseconds, high-density integration can be achieved, and it can be applied to future integrated optical switching and optoelectronic switching systems. The disadvantage is that the insertion loss is slightly larger and the isolation is low. At this stage, the more cutting-edge non-mechanical optical switches include MEMS optical switches, liquid crystal optical switches, thermo-optic effect optical switches, acousto-optic switches, and magneto-optical switches.

The magneto-optical switch is an all-optical switch that utilizes Faraday's magneto-optical effect to realize optical path switching. Compared with the traditional mechanical optical switch, the magneto-optical switch has the advantages of fast switching speed and high stability; and compared with other non-mechanical optical switches, it has the advantages of low driving voltage and small crosstalk. In recent years it has received more and more attention in the field of optical passive devices.

The magneto-optical effect refers to a physical phenomenon in which the polarization plane of linearly polarized light is rotated by the action of an external magnetic field when it propagates in a magnetic medium. Using the magneto-optic effect, the direction of the polarized light can be changed as needed, so that the synthesized output light reaches the designated port. Experiments show that the rotation angle of the polarized light vibration plane has a linear relationship with the magnetic induction intensity and the distance of propagation. The direction of optical rotation of magneto-optical materials has nothing to do with the direction of light propagation, but only with the direction of the applied magnetic field. When a positive magnetic field is applied to the magneto-optical crystal, the polarization plane of the linearly polarized light passing through the magneto-optic crystal will rotate forward; Reverse rotation. Magneto-optical materials generally use pure, Ce- and Bi-doped yttrium iron garnet (YIG) crystal materials, which have a large Verdet constant and small loss in the long-wavelength band.

In the existing magneto-optical switches, the commonly used components include magneto-optic crystals, polarization beam splitters, polarization beam combiners, birefringent crystals, λ/4 wave plates, right-angle prisms, collimating lenses and mirrors, etc. But there are following disadvantages.

1) The switching speed is low. The main performance parameters of the existing magneto-optical switch are: the switching speed is 20 microseconds to 1 millisecond, the insertion loss is 0.4-2.2 decibels, the crosstalk is 30-60 decibels, and the return loss is 50-60 decibels. Some of these magneto-optical switches can meet the basic requirements under the existing conditions, but obviously cannot meet the requirements of the rapidly developing all-optical network. These main performance parameters of magneto-optical switches are still far from the microsecond and nanosecond levels required by all-optical networks.

2) Difficult to array integration. Most of the existing magneto-optical switches use electric solenoids, which are large in size and low in utilization of the magnetic field. Meanwhile, the solenoid structure is not conducive to the large-scale integration of magneto-optical switches. This is far from the intensive multi-port input and output requirements of optical add-drop multiplexing systems, optical cross-connectors and optical routers required by all-optical networks.

3) The optical path of the present invention is simple, reducing the number of components and energy loss.

Contents of the invention

The purpose of the present invention is to provide a magneto-optical switch with no moving parts, fast switching speed, good stability, low driving voltage, small crosstalk, and small volume in view of the shortcomings of existing magneto-optical switches, such as low switching speed and difficulty in array integration. Reflective magneto-optical switches with advantages such as easy and high integration.

The technical solution of the present invention is to use three right-angle prisms to realize the switching of the optical path through light reflection, light splitting and light combining, so it is called a reflective magneto-optical switch.

The invention is provided with three right-angle prisms, a polarization beam splitter and a polarization rotation device. The input port of the first right-angle prism externally receives the incident light, and then enters the polarization beam splitter; the input port of the polarization beam splitter is externally connected to the output end of the right-angle prism, and decomposes the incident light to output two beams of orthogonally polarized P light and S light; S light is defined as the polarization component parallel to the light incident plane, and P light is defined as the polarization component perpendicular to the light incident plane; the input port of the second right-angle prism is externally connected to one end of the polarization beam splitter, and the incident light is reflected to the polarization Light rotation device; the right half of the polarized light rotation device is input to the output end of the external polarization beam splitter and the output end of the second right-angle prism, and the two beams of polarized light are output to the third right-angle prism from the output end of the left half part; The output light of the left half part of the third right-angle prism is externally connected to the polarization rotation device, and is reflected to the input port of the left half part of the polarization rotation device in the third right-angle prism, after passing through the polarization rotation device, a beam of polarized light goes to the first The two right-angle prisms are reflected to the polarization beam splitter and combined with another beam of polarized light, and enter the output port as required.

The polarization rotation device is composed of two Faraday rotators, that is, magneto-optical crystals.

In the reflective magneto-optical switch, the new reflected light is used to achieve the beam splitting and merging of the optical path, which greatly reduces the number of accessories, reduces the volume, and reduces the cost; the input and output ports are in the same plane, easy to integrate and control; reduce Drive voltage, reduce energy consumption.

The magneto-optical switch mainly utilizes Faraday's magneto-optic effect. With this feature, the magneto-optical switch can realize the all-optical switching function necessary for the all-optical communication network. Using the characteristics of magneto-optical rotating devices, polarizing beam splitters and rectangular prisms, a 1×2 magneto-optical switch can be designed to realize the all-optical switching function necessary for optical communication.

A beam of light is reflected to the polarizing beam splitter through the first right-angle prism, and the polarizing beam splitter can divide a beam of light into two orthogonal polarization states and output them to the second right-angle prism and the magneto-optical rotation device respectively; one of the polarized beams After passing through the second right-angle prism, it also exits to the magneto-optical rotating device. Two beams of polarized light go out to the third right-angle prism after passing through the magneto-optical rotation device and reflect to the magneto-optic rotation device. One beam of polarized light goes out directly to the polarization beam splitter, and the other beam of polarized light goes out to the polarizer after passing through the second right-angle prism. A beam splitter, where two beams of polarized light are combined. The magneto-optic rotating device is composed of two magneto-optic crystals. Under the control of the external electric field, the incident light will be output from different output ports.

The present invention changes the rotation effect of the magneto-optic crystal material on the polarization plane of the incident polarized light through the change of the external electric field, so as to achieve the effect of changing and switching the optical path. Therefore, compared with the existing magneto-optic switch, the present invention has the following outstanding advantages :

1) The reflective optical path is adopted, and the principle of the optical path is simple and practical. This has not been reported at home and abroad.

2) Both the right-angle prism and the magneto-optical rotating device have small dimensions, so that the dimensions of the present invention are greatly reduced compared with the existing magneto-optical switches.

3) The output and input ports of the present invention are on the same plane, the overall structure is easy to integrate and control, and the sensitivity of the reflective optical path is relatively improved.

4) The present invention uses fewer devices, greatly reducing the cost, and it is easy to use a plurality of parallel arrays or crossed optical switch arrays.

5) The driving voltage of the present invention is low, the utilization rate of the magnetic field of the magneto-optical rotating device is high, the required driving voltage is low, the energy consumption is low, and the temperature stability is relatively improved.

Description of drawings

FIG. 1 is a schematic diagram of the optical path of the embodiment of the present invention (1×2 reflective magneto-optical switch) when the high-speed magnetic field state is “ON”.

FIG. 2 is a schematic diagram of the optical path of the embodiment of the present invention (1×2 reflective magneto-optical switch) when the high-speed magnetic field state is “OFF”.

Fig. 3 is a distribution diagram of PRE state "ON" in the magneto-optical switch according to the embodiment of the present invention.

Fig. 4 is a distribution diagram of PRE state "OFF" in the magneto-optical switch according to the embodiment of the present invention.

Detailed ways

As shown in Figures 1-4, a light beam enters the first rectangular prism RAP1 from the right, and then enters the polarizing beam splitter PBS. The polarization component parallel to the light incident plane is defined as S light, and the polarization component perpendicular to the light incident plane is defined as P light. In the polarizing beam splitter PBS, the S light is reflected and the P light is transmitted, forming two outgoing light rays whose polarization planes are perpendicular to each other. Using the second right-angle prism RAP2 and the polarization beam splitter PBS, two mutually perpendicular light rays enter the polarization rotation element PRE in parallel. The S light and the P light enter the third right-angle shuttle mirror RAP3 from the polarization rotation element PRE, pass through the polarization rotation element PRE in reverse, and finally enter the second right-angle prism RAP2 and the polarization beam splitter PBS.

When PRE is in the "ON" state, the polarization planes of the two beams of light are rotated by 90°. The two beams of light are synthesized into one beam in the polarization beam splitter PBS, and output from the output port 1 through the first right-angle prism RAP1. When the polarization rotation element PRE is in the "OFF" state, the two beams of light maintain their original polarization states. Two beams of light are synthesized into one beam in the polarization beam splitter PBS, and output from output port 2. In a magneto-optical switch, the polarization state of the input light is independent of the operating state. The two light paths traveled by S light and P light are actually equal. Only one polarization rotation element PRE is needed to control the polarization states of the two polarized lights; one polarizing beam splitter PBS is used for splitting and combining the beams.

In the optical circuit layout of the magneto-optical switch, the polarization rotation element PRE is a core device. In Fig. 3 and Fig. 4, the polarization rotation element PRE of the optical path is composed of two Faraday rotators (magneto-optical crystals). When the magneto-optic crystals M-O(A) and M-O(B) are energized in opposite directions, one magneto-optic crystal rotates the polarized light by 22.5° each time, and the other magneto-optic crystal rotates the polarized light by -22.5° each time, and the polarized light rotates The component PRE has no polarization effect on polarized light as a whole, and the optical path is in a straight-through state. When the magneto-optic crystals M-O(A) and M-O(B) are energized in the same direction, the two magneto-optic crystals rotate the polarized light by 22.5° each time, and the polarization rotation element PRE rotates the polarized light by 90° as a whole, and the optical path in a cross state.

Claims (2)

1. A reflective magneto-optical switch is characterized in that 3 rectangular prisms, 1 polarizing beam splitter and 1 polarized light rotation device are provided; the input port of the first rectangular prism receives incident light externally, and then injects into Polarizing beam splitter; the input port of the polarizing beam splitter is externally connected to the output end of the first right-angle prism, and the incident light is decomposed to output two beams of P light and S light with orthogonal polarization states; S light is defined as incident light with the first right-angle prism The polarization component parallel to the plane, P light is defined as the polarization component perpendicular to the light incident surface of the first right-angle prism; the input port of the second right-angle prism is externally connected to one end of the polarization beam splitter, and the incident light is reflected to the polarization rotation device; the polarized light The right half of the rotating device is input to the output end of the external polarizing beam splitter and the output end of the second right-angle prism, and the two beams of polarized light are output to the third right-angle prism from the output end of the left half; the third right-angle prism is externally connected to the polarizing The output light of the left half of the light rotation device is reflected in the third right-angle prism to the input port of the left half of the polarization rotation device. After passing through the polarization rotation device, a beam of polarized light goes to the second right-angle prism and is reflected The polarization beam splitter is combined with another beam of polarized light, and enters the output port according to the switching requirements of the optical signal. 2. A reflective magneto-optical switch as claimed in claim 1, characterized in that said polarization rotation device is composed of two Faraday rotators, that is, magneto-optical crystals.

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