CN103576241B - Light-blocking type micro-electro-mechanical variable optical attenuator - Google Patents

Abstract

The invention discloses a light-shielding micro-electromechanical variable optical attenuator, which includes: input and output optical fibers, a fixed light-shielding plate, a movable MEMS device, a magnetic field generating device and a driving circuit; the center of the fixed light-shielding plate has a light hole, and the driving circuit The lower surface of the fixed shading plate is aligned and bonded to the upper surface of the movable MEMS device. The center of the movable MEMS device has a moving shading plate, and the magnetic field generating device is a central air leakage structure. The center of the movable MEMS device and the magnetic field generating device It is located on the same axis as the center of the light hole; wherein, the light is input from the input optical fiber, after passing through the light hole of the fixed light-shielding plate, and then the movable MEMS device produces controllable light attenuation, and then is output by the output fiber; the magnetic field The generating device interacts with the current passing through the movable MEMS device to generate Lorentz force, and drives the moving light shield to generate motion. The optical attenuation of the variable optical attenuator disclosed by the invention is continuously adjustable.

Description

A Light-shielding MEMS Variable Optical Attenuator

technical field

The invention relates to the field of optoelectronic technology, in particular to a variable optical attenuator, which can be used to produce controllable attenuation of the light intensity input therein.

Background technique

With the rapid growth of communication traffic and the diversification of business forms, all-optical networks have become the development trend of communication networks. One of the key problems to be solved in the practical application of optical networks is the unbalanced power among wavelength channels. In many cases, it is necessary to reduce the power of optical signals.

Optical Attenuator (OA) is a kind of optical attenuator (mechanical, electric, magnetic, etc.) that can realize the movement of optical elements or the change of optical state, thereby changing the transmission efficiency of light, and achieving the output optical power relative to A device that attenuates the input optical power. As an important passive optical power adjustment device, the optical attenuator can produce controllable attenuation in the optical network, and can be well matched with other devices to achieve optical gain flatness, dynamic gain balance and transmission power balance.

Optical attenuators can be divided into two types: fixed optical attenuator and variable optical attenuator (Variable Optical Attenuator, VOA). At present, the price of fixed optical attenuator is relatively low, and it is used to balance light energy. However, since the attenuation cannot be adjusted, dynamic control of the signal cannot be realized. Relatively, the variable optical attenuator has more advantages in development, and the attenuation can be changed. , can actively and accurately balance the optical power, and realize real-time processing of the signal, which is the focus of current research, and the future development will attract more attention. VOA can be used in the evaluation, research, adjustment and correction of optical communication lines and systems, etc. In optical communication networks, especially in wavelength division multiplexing (WDM) systems, VOA has a wide range of applications.

In order to better meet the needs of optical communication, VOA is developing towards the direction of high integration, miniaturization and low cost. At present, VOA has many different types of manufacturing technologies, mainly including adjustable mechanical technology, magneto-optical technology, liquid crystal technology, acousto-optic technology, thermo-optic technology, planar waveguide technology, MEMS technology and other forms. MEMS-based devices are small in size, good in performance, easy to implement arrays, and low in power consumption, and fully meet the needs of market development. VOA made with MEMS technology, in addition to maintaining the comprehensive optical performance of traditional technology VOA, also has the advantages of large attenuation range, small size, easy multi-channel integration, fast response speed, and high cost performance. It is considered to meet the requirements of future all-optical communication networks. One of the ideal devices. However, there are still some technical problems in the existing MEMS VOA: such as large driving voltage, poor linearity, reliability, etc., and there is still a certain distance from practical application.

Contents of the invention

In order to solve the above-mentioned problems in the prior art, the present invention provides a MEMS variable optical attenuator (VOA) based on electromagnetic drive to realize a variable optical attenuator (VOA) with simple structure, low cost, high reliability and practical application value. Attenuator.

In order to achieve the above object, the present invention provides a light-shielding micro-electromechanical variable optical attenuator, which includes: input and output optical fibers, a fixed light-shielding plate, a movable MEMS device, a magnetic field generating device and a drive circuit; the center of the fixed light-shielding plate has a The light hole, drive circuit and the lower surface of the fixed light shield are aligned and bonded to the upper surface of the movable MEMS device. The center of the movable MEMS device has a movable light shield, and the magnetic field generating device is a central leaky structure. and the center of the magnetic field generating device 8 and the center of the light hole 2 are located on the same axis; wherein, the light is input from the input optical fiber, after passing through the light hole of the fixed light-shielding plate, and then the movable MEMS device generates controllable light attenuation, The output is output by the output optical fiber; the magnetic field generating device provides an axial magnetic field parallel to the light beam, interacts with the current passing through the movable MEMS device to generate Lorentz force, and drives the moving shading plate to generate motion.

As can be seen from the foregoing technical solutions, the present invention has the following beneficial effects:

The light-blocking micro-electromechanical variable optical attenuator provided by the present invention can attenuate optical signals in free space, and the corresponding wavelength-related loss, polarization-related loss and insertion loss are all lower than other methods, and the optical performance is good. At the same time, it avoids problems such as complex optical fiber alignment required by the reflective structure, has a large attenuation range, and has good dynamic characteristics, and can be widely used in optical communication networks.

The light-blocking micro-electromechanical variable optical attenuator provided by the present invention uses an electromagnetic drive method based on Lorentz force, which can provide a large driving force without hysteresis effect, and realizes low-voltage drive and fast response. It satisfies the requirement of fast and low power consumption development of the optical communication network well.

The light-shielding micro-electromechanical variable optical attenuator provided by the present invention is processed and manufactured by microelectronic technology, and has a simple structure. By using a combination of a fixed light-shielding plate and a movable MEMS device, the area of the light beam is effectively controlled, and the device size is reduced. The size can be integrated with CMOS devices, providing the basis for optoelectronic integration.

Description of drawings

Fig. 1 is a schematic structural view of a light-shielding micro-electromechanical variable optical attenuator in the present invention;

Fig. 2 (a)～Fig. 2 (c) are the attenuation effect diagrams of the light blocking type MEMS variable optical attenuator in the present invention;

Fig. 3 (a)～Fig. 3 (b) are the structural representations of movable MEMS device among the present invention;

Fig. 4 is a schematic diagram of the movement of the movable shading plate driven by Lorentz force in the present invention.

Detailed ways

In order to make the object, technical solution and advantages of the present invention clearer, the present invention will be further described in detail below in conjunction with specific embodiments and with reference to the accompanying drawings.

FIG. 1 shows a schematic structural diagram of a light-shielding MEMS variable optical attenuator disclosed in the present invention. As shown in FIG. 1 , the variable optical attenuator includes an input optical fiber 1 , an output optical fiber 10 , a fixed shading plate 3 , a drive circuit 4 , a movable MEMS device 6 , a magnetic field generating device 8 , and a movable shading plate 9 . Wherein, the fixed light-shielding plate 3 and the movable MEMS device 6 are respectively manufactured by using micro-electro-mechanical technology on different substrates. The fixed shading plate 3 can be made of silicon chips, glass sheets or other materials, and the surface is coated with a reflective film. The reflective film on the surface can be thin film materials with reflective properties such as gold and aluminum. The center of the fixed shading plate 3 has a light hole 2, The size of the opened light hole 2 is related to the size of the light beam, and is used to limit the size of the light spot and diffraction and other phenomena. The driving circuit 4 provides controllable driving power for the device. The drive circuit 4 and the lower surface of the fixed light shielding plate 3 are aligned and bonded to the upper surface of the movable MEMS device 6 through the first bonding layer 5; They are bonded to each other via the second bonding layer 7 . The center of the movable MEMS device 6 is a moving visor 9, the magnetic field generating device 8 is a ring structure with an open center, and the center of the movable MEMS device 6 and the magnetic field generating device 8 is located on the same axis as the center of the light through hole 2 superior. The output optical fiber port 10 is opposite to the input optical fiber port 1, the fixed shading plate 3 and the movable MEMS device 6 are located between the input and output optical fibers, the light is input by the input optical fiber, first passes through the light hole 2 of the fixed shading plate 3, and then passes through the movable After the dynamic MEMS device 6 produces controllable light attenuation, it is output by the output optical fiber. The magnetic field generating device 8 can provide an axial magnetic field parallel to the light beam, interact with the current passing through the movable MEMS device 6 structure, generate Lorentz force, and provide a drive to move the movable visor 9, as shown in FIG. 4 . If the moving shading plate 9 of the movable MEMS device 6 does not block the light-through hole 2 of the fixed shading plate 3, after the light beam is emitted from the input optical fiber, it can enter the output optical fiber through free propagation to realize optical signal output and form a complete optical path ; If the moving shading plate 9 blocks the light hole 2 completely, the beam cannot enter the output fiber, and the optical signal is completely attenuated; if the moving shading plate 9 partially blocks the light hole 2, the light beam partly enters the output fiber and passes through the Loren By controlling the moving position of the moving light shield 9, the area of the light hole 2 blocked by the moving light shield 9 can be controlled, and the intensity of the optical signal entering the output optical fiber can be controlled, thereby producing controllable light attenuation. The intensity of the light signal is proportional to the light-passing area; the light-passing area is proportional to the displacement of the moving visor 9; for elastic structures, the displacement of the moving visor 9 is proportional to the size of the Lorentz force; and the Lorentz The magnitude of the force is directly proportional to the drive current. Therefore, the optical attenuation of the variable optical attenuator driven by Lorentz force has a linear relationship with the driving current, and linear continuous control can be realized.

Fig. 2(a)-Fig. 2(c) show the structural diagrams of three optional embodiments of the light-shielding MEMS variable optical attenuator in the present invention. As shown in Figure 2(a)-Figure 2(c), the surface of the fixed light-shielding plate 3 is coated with a reflective film and has a light hole 2. The reflective film on the surface can be a film material with reflective properties such as gold and aluminum. , light can only pass through the light hole; if the moving light shield 9 of the movable MEMS device 6 does not block the light hole 2 of the fixed light shield 3 (as shown in Figure 2(c)), the light beam is emitted from the input optical fiber Finally, it can enter the output optical fiber after free propagation to realize optical signal output and form a complete optical path; if the moving light shield 9 completely blocks the light hole 2 (as shown in Figure 2(a)), the light beam cannot enter the output optical fiber , the optical signal is completely attenuated; if the moving light shield 9 partially blocks the light hole 2 (as shown in Fig. The size of the optical fiber can control the intensity of the optical signal entering the output fiber, which can produce controllable optical attenuation.

The light-blocking micro-electromechanical variable optical attenuator is driven by Lorentz force, and the magnetic field generating device 8 is an annular permanent magnet for providing an axial magnetic field.

3(a)-3(b) show the schematic structural diagrams of the movable MEMS device in the present invention. As shown in FIG. 3( a ), the movable MEMS device 6 is made of a silicon wafer and is composed of a folded beam with a moving light shield 9 in the middle of the folded beam. As shown in FIG. 3( b ), the movable MEMS device 6 is composed of a straight beam with a moving light shield 9 in the middle of the straight beam. The beams are elastic and act as springs in the MEMS structure.

Fig. 4 shows a schematic diagram of the motion of the movable shade driven by Lorentz force in the present invention. As shown in Figure 4, in the longitudinal magnetic field, when a steady current passes through the beam, the current interacts with the magnetic field to generate a transverse Lorentz force. The generated Lorentz force drives the deformation of the beam structure, and the movement of the movable light shield 9 causes the relative position between the movable light shield 9 and the light hole 2 to change, thereby realizing the control of the intensity of the optical signal entering the output optical fiber.

After the beam of the movable MEMS device 6 is deformed, an elastic restoring force will be generated due to the elasticity of the structure, and the magnitude of the elastic force is proportional to the displacement of the structure. When the structure is stable, the elastic force is equal to the Lorentz force. The Lorentz force is proportional to the driving current, so the displacement of the structure can be controlled by controlling the magnitude of the current, and then the amount of light attenuation can be controlled. Under a stable magnetic field, the Lorentz force generated by the current can accurately determine the displacement of the moving visor 9, and continuously variable light attenuation can be obtained by using a continuously variable current. Since the elastic force is proportional to the displacement of the structure, and the Lorentz force is proportional to the current, the displacement of the structure is proportional to the driving current under the condition of a certain magnetic field and structure, and the current can be used to realize linear control of the optical attenuator.

Since the size of the light beam in the optical fiber is generally very small, usually between a few microns and tens of microns, the light hole 2 of the light baffle 3 fixed between the input optical fiber and the output optical fiber not only ensures the normal passage of the light beam, but also limits the diffraction of light function, so that the spot area of the light beam at the position of the movable MEMS device 6 is very small. In order to realize the state switching between light completely passing through and completely attenuating, the distance that the movable light shield 9 needs to move is equal to the size of the light spot, so the displacement required by the structure is also several microns to tens of microns, and the driving current of the device can be limited to On the order of a few milliamps to tens of milliamperes.

Because the Lorentz force generated by the interaction between the current and the magnetic field has no hysteresis effect, the MEMS device can move quickly, so the variable optical attenuator can realize fast switching between different states.

In the above scheme, the relative relationship between the light hole 2 of the fixed shading plate 3 and the initial position of the moving shading plate 9 when no driving current is applied can be based on specific needs by simply installing the fixed shading plate and the movable MEMS device. Adjust the alignment position of the fixed shading plate 3 and the movable MEMS device (6), which can be set to a state where the moving shading plate 9 completely covers or fully exposes the light hole 2, or can be set to be partially covered state. The structure and process difficulty will not be increased, and the power consumption of the attenuator can be reduced.

In the above solution, the magnetic field generating device 8 can also be an electromagnet composed of a energized solenoid or other devices with a hollow center that can generate a relatively uniform axial magnetic field, and can achieve the same effect.

The specific embodiments described above have further described the purpose, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above descriptions are only specific embodiments of the present invention, and are not intended to limit the present invention. Within the spirit and principles of the present invention, any modifications, equivalent replacements, improvements, etc., shall be included in the protection scope of the present invention.

Claims (9)

1. A light-shielding type micro-electromechanical variable optical attenuator, which includes: input and output optical fibers, a fixed light-shielding plate, a movable MEMS device, a magnetic field generating device and a drive circuit; the center of the fixed light-shielding plate has a light-through hole, the drive circuit and the fixed light-shielding plate The lower surface of the shading plate is aligned and bonded to the upper surface of the movable MEMS device. The center of the movable MEMS device has a moving shading plate, and the magnetic field generating device is a central leaky structure, and its upper surface is glued to the lower surface of the movable MEMS device. combined, and the center of the movable MEMS device and the magnetic field generating device is on the same axis as the center of the light hole; Among them, the light is input from the input optical fiber, after passing through the light hole of the fixed light shielding plate, and then the movable MEMS device produces controllable light attenuation, and then is output by the output optical fiber; the magnetic field generating device provides an axial magnetic field parallel to the light beam , interacting with the current passing through the movable MEMS device to generate a Lorentz force, driving the moving light shield to generate motion. 2. A light-shielding micro-electromechanical variable optical attenuator as claimed in claim 1, characterized in that: said fixed light-shielding plate and movable MEMS device are located between input optical fiber and output optical fiber, said output optical fiber port and The ports of the input fibers are opposite, and their centers are on the same axis; after the light beam is emitted from the input fiber, it can enter the output fiber after free propagation to realize the output of the optical signal and form a complete optical path; by controlling the moving shading plate of the movable MEMS device The relationship between the light-passing hole and the fixed light-shielding plate can control the strength of the light signal entering the output optical fiber to realize controllable light attenuation. 3. A light-shielding micro-electromechanical variable optical attenuator as claimed in claim 1, characterized in that: the fixed light-shielding plate is a silicon wafer or a glass wafer, and the surface is coated with a reflective film; the reflective film on the surface has a reflective film. The performance of the film material; the size of the light hole is related to the size of the light beam. 4. A light-shielding micro-electromechanical variable optical attenuator as claimed in claim 1, characterized in that: the movable MEMS device is composed of a beam structure with a movable light-shielding plate in the middle, and the beam structure can pass through Elastic structure of electric current. 5 . The light-shielding MEMS variable optical attenuator according to claim 4 , wherein the beam structure is a folded beam structure or a straight beam structure. 6. A light-shielding micro-electromechanical variable optical attenuator as claimed in claim 1, characterized in that: said variable optical attenuator is driven by Lorentz force, and said movable MEMS device is driven by a driving circuit Provide a stable current, the current interacts with the magnetic field generated by the magnetic field generating device to generate Lorentz force, and the generated Lorentz force drives the movement of the moving shading plate to realize light attenuation; the movement shading can be controlled by controlling the magnitude of the current The position of the plate can realize the control of light attenuation; the displacement of the moving shading plate has a linear relationship with the driving current, which can realize the linear control of light attenuation. 7. A light-shielding micro-electromechanical variable optical attenuator as claimed in claim 1, characterized in that: the relative relationship between the light-through hole of the fixed light-shielding plate and the initial position of the moving light-shielding plate when no driving current is applied is based on the specific Adjustments are required. 8. A light-shielding micro-electromechanical variable optical attenuator as claimed in claim 7, characterized in that: the initial position of the moving light-shielding plate and the light-through hole is such that the moving light-shielding plate completely covers the light-through hole and fully exposes clear holes or partially cover clear holes. 9. A light-shielding micro-electromechanical variable optical attenuator as claimed in claim 1, characterized in that: said magnetic field generator is an annular permanent magnet or an electromagnet composed of an energized solenoid.