Numerical Model of Optical Switch Based on 2D MEMS

Transcription

1 POSTER 2015, PRAGUE MAY 14 1 Numerical Model of Optical Switch Based on 2D MEMS Michaela SOLANSKA 1, Jana SAJGALIKOVA 2 1,2 Dept. of Telecommunications and Multimedia, Faculty of Electrical Engineering, University of Zilina, Univerzitna 8215/1, Zilina, Slovakia michaela.solanska@fel.uniza.sk, jana.sajgalikova@fel.uniza.sk Abstract. With the growing demand for greater quantities of data and higher transmission speed, optical networks have an imant role in global communication infrastructure. Network service providers are looking for new technologies and innovation that can increase transmission capabilities of optical networks. An imant part of future optical networks are optical switches. Optical switches based on microelectromechanical systems (MEMS) technology are currently widely applicable and represent a very promising technology for quick transmission speeds of optical switching networks. In this paper, we present a design of an optical network consisting of four switching nodes and results of switching structure simulations, which is formed by the 2 dimensional MEMS (2D MEMS) switches. Keywords Optical switching, MEMS technology, 2D MEMS optical switches. 1. Introduction The data transmission by optical networks has an upward trend, therefore high-speed optical networks will need high performance nodes, which can handle the growing flexibility and effectiveness. Very imant part of high performance nodes is optical switching technology. Optical switches provision the optical paths (an optical path is a connection between two network nodes that is set up by assigning a dedicated wavelength to it on each link in its path) [1]. Currently, several switching technologies are available, e. g. optomechanical switches, MEMS switches, electrooptical switches, thermooptical switches, liquidcrystal switches, bubble switches, acoustooptical switches, switches based on semiconductor optical amplifier (SOA), switches based on fiber Bragg grating (FBG). From aforementioned switching technologies the most widely used technology is MEMS. MEMS technology allows us to build the cost-effective and high-capacity optical crossconnects [1-4]. The paper is organized as follows. Section 2 describes MEMS technology and the usage of MEMS technology in optical networks such as optical switches. Section 3 describes 2D MEMS optical switches. The simulation of switching structure, which is formed by 2D MEMS optical switches, is reed in section 4. The conclusion is drawn in section MEMS technology Micro-opto-electro-mechanical systems (MOEMS) are commonly known as optical MEMS, which are formed by combination of electrical, mechanical and optical components made by the micro system technologies. In general, they are made of silicon substrates. From a single silicon substrate it is possible to make several MEMS devices of size, which is in order from micrometers to millimeters. For MEMS realization the several technological procedures are used, for example surface and bulk micromachining, technology of HEXSIL, HARPSS, LIGA and others [4-10]. MEMS technology and surface micromachining led to the development of miniature optical devices, which are usable in many applicable areas. This is due the unique features of MEMS, which are applicable in realization, system integration and operation of micro-optical systems. Mechanical accuracy of MEMS, production micro system technology and optical functionality enables usage of wide amount of different movable and tunable mirrors, lenses, filters and other optical structures. Mechanical accuracy and controlling of these systems are provided by electrostatic, magnetic, thermal and pneumatic actuators. Great amount of electromagnetic modes, which could be adapted by micromirrors and diffractive optical MEMS in combination with their accuracy are used in optical fiber filters, including dispersive capacitors. The development of integrated optics, integrated electronics and mechanics allows the progress in biomedical devices, in which integration of miniature optical detection systems with micro fluidics provide smaller, quicker, multipurpose and cheaper systems. Exact dimensions and layout makes optical MEMS sensors usable for a variety of difficulty measurements. Photonic crystals and micro cavities, which represent the best of miniature optical components, allow further optical MEMS scalability [5-8]. Over the past decade, MEMS devices have spread to many applicable areas of wireless and optical telecommunication networks. With the increasing demand for more data and higher transmission speed, optical

2 2 M. SOLANSKA, J. SAJGALIKOVA, NUMERICAL MODEL OF OPTICAL SWITCH BASED ON 2D MEMS networks play an imant role in the global communication infrastructure. Network service providers are always looking for the latest technology and innovation, by which they can increase the bandwidth. MEMS technology in optical networks is used for display applications and switches (wavelength selective switches and free space switches 1xN, NxN) [5-8]. To switch information from the input s to the relevant output s, we can use optical MEMS switches. MEMS technology offers a big switching matrix with low losses in optimal costs. Optical MEMS switches provide wavelength insensitivity, polarization insensitivity, scalability, very low crosstalk, quick switching speeds in order from miliseconds to hundreds of microseconds. Due to this, optical switches based on MEMS technology are currently widely applicable and represent a very promising technology for quick transmission speeds of optical switching networks [5]. Optical MEMS switches can be categorized into three groups: MEMS switches using micromirror, MEMS switches using membranes, MEMS switches using plane moving waveguides. The first two groups represent free space switches, because they use space as transmission medium. The last group represents waveguide switches that require moving certain parts of the switch once functioning. Most of the optical MEMS switches use micromirrors, which can be divided into two groups, namely, 2 dimensional MEMS (2D MEMS) and 3 dimensional MEMS (3D MEMS) [5, 11]. 3. 2D MEMS optical switches In 2D MEMS optical switches the micromirrors are arranged in a crossbar configuration. Micromirrors work in digital mode, it means that each micromirror has only two positions, so their position is bistable (ON/OFF) [5]. The bistable position of micromirrors greatly simplifies the control mechanism [4]. The example of 2D MEMS switch is shown in Fig. 1. 2D MEMS switch uses a crossbar configuration. It has 4 input s, 4 output s and several deflecting micromirrors, which ensure cross-functionality. If the switch is in the ON position, optical beam passing through the input s will spread along the switch fabric. Set micro-mirrors deflected optical beam to the output. If the switch is in the OFF position, optical beam will pass through the switch fabric to the output s without micro-mirrors deflection. Switch with this type of configuration can simultaneously transmit and receive several signals. During the transmission some of the transmitted signals can be switched to the drop s and new input signals can be added in the add s. This type of working switch is Fig. 1. 2D MEMS optical switch. referred to as Optical add-drop multiplexer (OADM), which can be used for the adding or dropping of optical channels. Signal loss increases with connection length (and with size of switching structure) [12-13]. In 2D MEMS switches the insertion losses are increasing. This is due to asymmetric Gaussian spread of the optical beam. Due to the high insertion losses the 2D MEMS switches are not suitable for large size (N>32) [3-5]. 2D MEMS technology can deliver a range of applications including medium-sized and large optical cross-connects, wavelength selective optical crossconnects, wavelength add-drop multiplexing, optical service monitoring, and optical protection switching. MEMS technology is an imant key to ensuring reliability and flexibility of a network [11-13]. 4. Simulation results The 2D MEMS switch is managed by the control bits 0 and 1. If the switch is managed by control bit 0, the input s will be switched unchanged to output s. Otherwise, if the switch is managed by control bit 1, the INPUT will be switched to the DROP and the ADD to the OUTPUT, as shown in Tab. 1. Table 2 shows the individual wavelengths entering and leaving the s of all nodes, which is shown in Fig. 4, 5, 6, 7. Node Switch Control A 0 B 0 C 1 D 1 Tab. 1. Switch Control.

3 POSTER 2015, PRAGUE MAY 14 3 Node Add Drop Input Output A 1553 nm 1553 nm 1552 nm 1552 nm B 1552 nm 1552 nm 1552 nm 1552 nm C 1553 nm 1552 nm 1552 nm 1553 nm D 1552 nm 1553 nm 1553 nm 1552 nm Tab. 2. Wavelengths of the individual s of all nodes. Principle integration of the simulation network is shown in Fig. 2. Two bitstreams enter input node A on the wavelengths 1553 nm (frequency THz) and 1552 nm (frequency THz). The A node is set to switch from the input INPUT to the output OUTPUT, and from the input ADD to the output DROP. The output of the A node is connected to the input of the B node. The information on wavelength 1552 nm is brought to the input ADD of the B node. Node B has the same configuration as the node A, so the information from the input INPUT is switched to the output OUTPUT and the information from the input ADD is switched to the DROP. Output of the node B is connected to the input of the node C. Node B has the same configuration as the node A, so the information from the input INPUT is switched to the output OUTPUT and the information from the input ADD is switched to the DROP. Output of the node B is connected to the input of the node C. Fig. 2. Principle scheme of optical network. To the input ADD of the node C is brought the information from the DROP of the node A. To the input ADD of the node C is brought the information from the DROP of the node A. The C node is set to switch from the input INPUT to the output DROP and from the input ADD to the output OUTPUT. Output of the C node is connected to the input of the D node. The new information on the wavelength 1552 nm is brought to the input ADD of the D node. Node D has the same configuration as the node C, so the information from the input INPUT is switched to output DROP and information from the input ADD is switched to the output OUTPUT. The output of the D node is connected to the input of the A node. Fig. 3. Scheme of optical network in simulation software.

4 4 M. SOLANSKA, J. SAJGALIKOVA, NUMERICAL MODEL OF OPTICAL SWITCH BASED ON 2D MEMS Figure 3 shows the optical network created in the simulation software VPIphotonics. Optical network consists of four nodes, and as simulation parameters were chosen bit rate 10 Gbit/s, average power of lasers were set to 1 mw and crosstalk to 60 db. OOK transmitters (standard transmitters in optics with ON/OFF modulation) are used as inputs. Switching structure is formed by 2D MEMS optical switch. The 2x2 switch is controlled by the bit value of the element Const. Since the switch block in the simulation software is recognized as ideal, i.e. the switching time cannot be set, we used a delaying element, whose value we set according to [7]. To see the results we used analyzer block. Block Fork is used as a passive hub. 5. Conclusion In this paper we present MEMS technology, which is used in optical networks for optical switching due to the unique optical features of the optical MEMS switches. MEMS switches are divided to the two groups, 2D MEMS a 3D MEMS. The paper also includes the proposition of the optical network, which was created in the simulation software VPIphotonics. The designed optical network contains four switching nodes and results of the simulations show that the low crosstalk, fast switching speed and low input losses are the main advantages of MEMS. Currently we are creating an optical network in simulation software. The optical network will be created by 3D MEMS switches, due to the large switching structure and due to the fact that insert losses do not increase with the number of s. This implies that MEMS switches represent a promising technology for the improvement of the transmission abilities of the optical networks. Fig. 4. Optical spectrum from output of the A node. Acknowledgements This paper was supervised by prof. Ing. M. Dado, PhD. and Ing. M. Markovic, PhD., FEL ZU in Zilina. This work is suped by the Slovak Research and Development Agency under the project APVV ("Mitigation of stochastic effects in high-bitrate all-optical networks"). Fig. 5. Optical spectrum from output of the D node. References [1] PAPADIMITRIOU, G., PAPAZOGLOU, CH., POMPORTSIS, A. Optical Switching. Hoboken: Wiley, [2] SHEN, G., CHENG, T. H., BOSE, S. K., Architectural design for multistage 2-D MEMS optical switches. Journal of Lightwave Technology, 2002, vol. 20, iss. 2, p Fig. 6. Optical spectrum from add of the D node. Fig. 7. Optical spectrum from drop of the D node. [3] CHU, P. B., LEE, S. S., PARK, S. MEMS: The path to large optical crossconnects. IEEE Communications Magazine, 2002, vol. 40, iss. 3, p [4] YEOW, T. W., LAW, K. L., GOLDENBERG, E. A. MEMS optical switches. IEEE Communications Magazine, 2001, vol. 39, iss. 11, p [5] THAKULSUKANANT, K. MEMS technology for optical switching. Walailak Journal of Science & Technology, 2013, vol.10, iss. 1, p. 9. [6] SOLGAARD, O. Optical MEMS: From micromirrors to complex systems. Journal of Microelectromechanical Systems, 2014, vol. 23, iss. 3, p [7] YANG, Y. J., LIA, B. T. A novel 4 4 optical switching using an anisotropically etched micromirror array and a bistable mini-actuator array. IEEE Photonics Technology Letters, 2009, vol. 21, iss. 2, p [8] FAN, K. CH., LIN, W. L., CHAING, L. H., CHEN, S. H. A 2 2 mechanical optical switch with a thin MEMS mirror. Journal of Lightwave Technology, 2009, vol. 27, iss.9, p [9] HUSAK, M. MEMS and microsystems technologies. Automa, 2008, vol. 11, p. 7.

5 POSTER 2015, PRAGUE MAY 14 5 [10] HUSAK, M. Usage of the MEMS in the industry. Automa, 2008, vol. 12, p. 14. [11] XIAOHUA, M., KUO, G. S. Optical switching technology comparison: optical MEMS vs. other technologies. IEEE Communications Magazine, 2003, vol. 41, iss. 11, p [12] YADAV, R., AGGARVAL, R. R. Survey and comparison of optical switch fabrication techniques and architectures. Journal of Computing, 2010, vol. 2, iss. 4. [13] DE DOBBELAERE, P., FALTA, K., GLOECKNER, S. Advances in integrated 2D MEMS-based solutions for optical network applications. IEEE Communications Magazine, 2003, vol. 41, iss. 5, p About Authors Author-Michaela SOLANSKA was born in Ruzomberok, Slovakia in the In 2012 she finished MSc at University of Zilina, Faculty of Electrical Engineering, Department of Telecommunications and Multimedia. Currently she studies doctor degree, her research interests include reservation protocols and optical switching in highspeed optical networks. Co-author-Jana SAJGALIKOVA was born in Brezno, Slovakia in the In 2013 she finished MSc at University of Zilina, Faculty of Electrical Engineering, Department of Telecommunications and Multimedia. Currently she studies doctor degree. Her research is focused on numerical modelling of selected parts of optical communication systems and their applications in highspeed optical networks.