MEMS (Micro-Electro-Mechanical Systems) is a mass-produced micro device or system that integrates micro-machines, micro-actuators, signal processing, and control circuits. MOEMS is an abbreviation of Micro-Opto-Electro- Mechanical System, which means micro-opto-electro-mechanical systems that apply micro-optics to micro-electromechanical systems. This is an important application of MEMS in optical communications. A micro-opto-mechanical chip generally refers to an optical system or an optoelectronic system that includes more than one micro-mechanical element, and its application will cover various aspects such as optical communication, optical display, data storage, adaptive optics, and optical sensing.
With the rapid development of optical communications, the status of optical interconnection and optical switching as an optical network node is becoming more and more important. The optical switching device is a system component that uses light as a core to realize light on/off and cross-connection. There is no photoelectric conversion. MEMS optical switches have the advantages of low loss and high stability, and are independent of the transmitted data rate and signal protocol. Practical MEMS optical switch principle is very simple, its structure is essentially a two-dimensional micro-lens array, when the light exchange, by moving or changing the lens angle, the light is directly sent to or reflected at the output of the optical switch. MEMS optical switches are based on the principle of using mechanical switches, but they can be integrated on monolithic silicon substrates like waveguide switches. Therefore, they combine the advantages of mechanical optical switches and waveguide optical switches, while overcoming their inherent disadvantages. MEMS optical switches have greatly improved response speed and reliability, low insertion loss and crosstalk, low polarization and wavelength-dependent loss, good adaptability to different environments, low power and control voltage, and latching.
2 MEMS optical switch control principle2.1 Introduction to MEMS Optical Switch
Typical MEMS optical switching devices can be divided into two-dimensional and three-dimensional structures. The two-dimensional MEMS spatial rotating mirror is monolithically integrated on the silicon substrate by surface micro-machined technology, and the collimated light is appropriately coupled to the appropriate output through the micro-mirror. The micro hinge hinges the micro-mirror on the silicon substrate, and two push rods are arranged on both sides of the micro-mirror. One end of the push rod is connected with the hinge point of the micro-mirror, and the other end is connected with the translating dressing electrode. The switching state is achieved by rotating the micromirror by adjusting the dresser electrode. When the micromirror is horizontal, the light beam can pass over the micromirror, and when the micromirror is rotated perpendicular to the silicon substrate, it will reflect the light beam incident on its surface. Thus, the light beam is output from the corresponding output port of the micromirror. The mirrors of the three-dimensional MEMS can be deflected in any direction. These arrays usually appear in pairs. The input light reaches the mirror of the first array and is reflected to the mirror of the second array, and then the light is reflected to the output port.
Among various possible driving methods, electrostatic and magnetic induction methods are the main options. The electrostatic method relies on mutual attraction between mechanical elements with opposite polarity of charge, which is the main driving method used in MEMS technology, and it has the advantages of repeatability and easy shielding. Magnetic induction drives rely on mutual attraction between magnets or electromagnets. Although the magnetic induction drive can generate more driving force and has higher linearity, there are still many problems to be solved in magnetic induction applications, so the current electrostatic drive scheme is still the best choice for reliable equipment.
The control scheme described in this paper addresses the two-dimensional structure of MEMS optical switches driven by electrostatic methods.
2.2 Control Principles and Processes
The MEMS 4&mes;4 optical switch is one of the core subsystems in the OXC node device. In the entire system, it is responsible for routing the four wavelengths of light in accordance with requirements in order to achieve the purpose of optical switching.
The advantage of the MEMS optical switch is that the switching of the optical wave route is accomplished through the external control information and the corresponding high and low level control of the internal 16 micro lens lift up or not. The MEMS optical switch we have chosen specifies the format of the control information. Regardless of how many microlenses there are, a series of 64-bit serial data consisting of “1†and “0†are required to complete the control.
According to the specific working principle of the MEMS optical switch and the timing relationship between the required digital signals, the required 64-bit control information and other signals (such as CLK and ENA signals) can be provided by a high-speed single-chip microcomputer.
The control system simulates the local control and issues corresponding routing information by a PC program during board debugging. The PC's information is sent to the MCU via the serial port, and the MCU performs further control actions. The information such as the success or failure of the MEMS optical switch routing is read by the SCM to read the 64-bit control data in its internal registers and compared with the original correct 64-bit data. After the operation is completed, the SCM again generates corresponding feedback information to the PC through the serial port. Form human-computer, remote and local interactions.
In order to maintain compatibility with the entire OXC system, the MEMS subsystem, in addition to being controlled by a local microcontroller, should also be directly controlled by an FPGA chip in a dedicated main control circuit. In this way, you can ensure that the subsystem is completely safe. For this reason, the circuit design will also retain its interface.
3 control system designBased on the foregoing principles, the design of this subsystem will be divided into hardware and software design.
3.1 Hardware Design
The test phase will design four control channels for the MEMS, which will retain the manufacturer's test board circuit and use it as a control channel; provide two channels for different types of control information of the local microcontroller; besides, it will control the FPGA chip that may be used in the future. Information is reserved for one channel. The actual application stage will only retain one microcontroller channel and one FPGA control channel.
During debugging of the board, the routing and management information comes from the PC software of the simulation network management. In practical applications, all routing and management information will be autonomously controlled by the board. Figure 1 is a hardware design block diagram.
Although there are more than one control channel in the experimental and practical stages, only one channel is active in a certain period. The switching of channels is done by manual jumpers.
Single-chip microcomputer selection of high-speed low-power dual-serial multi-interrupt microcontroller. This MCU will provide 64-bit control information and other control signals required for the MEMS optical switch, such as the clock CLK signal, routing enable signal and so on.
The parallel-serial conversion circuit is used to convert the control information sent by the single-chip microcomputer in parallel into serial data required by the MEMS. This function is accomplished by the microcontroller and the parallel-to-serial conversion chip; the serial-to-parallel conversion circuit is used by the microcontroller to read serial primary routing information in the MEMS internal registers in parallel. This function is accomplished by the microcontroller and the serial-to-parallel conversion chip.
3.2 Software Design Scheme:
Because it requires human-computer interaction in debugging, it requires a set of PC program and SCM control program. The two programs communicate via the RS-232 interface. The communication protocol between programs is formulated as follows:
(1) Data sent from the PC to the microcontroller
The PC program uses a graphical interface, and various information sent and received will be given to the administrator in real time on the program interface. Figure 2 shows the flow chart of PC network management simulation program.
Compared with the PC program, the difficulty of the SCM control program is that it needs to send the clock signals and enable signals needed by the MEMS, as well as send 64-bit micro lens control data. There is a strict timing relationship between these signals. Special attention should be paid to programming and instruction writing techniques when programming. Microcontroller program flow chart, shown in Figure 3.
Through the coordination of software and hardware, the MEMS optical switch subsystem can smoothly complete any switching of multiple optical routes. During the debugging stage, the administrator uses computer software to simulate the NMS sending routing control commands to the MCU on the MEMS control board. In practical applications, this routing control instruction is issued by the main control board in the system. After the MCU receives the instruction, a specific instruction meeting the control requirements of the MEMS optical switch is issued to control the corresponding actions of the internal lens of the MEMS optical switch, thereby completing the cross-connection of the optical path. This process does not require any photo-electric conversion.
Plug-In Connecting Terminals,Insulated Spade Terminals,Cable Connector Double Spade Terminals,Vinyl-Insulated Locking Spade Terminals
Taixing Longyi Terminals Co.,Ltd. , https://www.lycopperlugs.com