The working principle and application of MEMS optical switch

This article will including:

• What is optical switch?
• Working principle of MEMS optical switch
• Structure of MEMS fiber optic switch
• MEMS optical switch VS Mechanical optical switch
• The advantages of MEMS switch
• The applications of MEMS fiber optic switch
• The MEMS based optical switch in AON

What is optical switch?

Optical switch is a device that converts an optical signal from one optical channel to another optical channel within a certain range. It has one or more selectable transmission windows. Fiber optic switch is one of the core devices for optical cross-connection, optical add/drop multiplexing, network monitoring and automatic protection system.

Its implementation technologies are diverse, including: mechanical optical switches, thermo-optical switches, acousto-optic switches, electro-optical switches, magneto-optical switches, liquid crystal optical switches and MEMS optical switches. The traditional switch with electricity as the core is gradually unable to meet the demand for high-speed and large-capacity optical communication, which is why the all-optical switch appears in the market. Among them, MEMS optical fiber switches are widely used due to their small size, low power consumption, and good scalability.

Working principle of MEMS optical switch

What is MEMS? MEMS is shot for Micro-Electro-Mechanical System, which refers to a micro-device or system that can be mass-produced and integrate micro-machines, micro-actuators, signal processing and control circuits. The preparation process of micro-mechanical structures includes photolithography, ion beam Etching, chemical etching, wafer bonding, etc.

MEMS is driven by electronic technology, such as electrostatic attraction, electromagnetic force, electrostriction, and thermocouple. Among all the driving mechanisms of MEMS devices, the electrostatic attraction structure is the most widely used due to its simple preparation, easy control and low power consumption.

The MEMS optical switch is to engrave a number of tiny mirrors on the silicon crystal. The microarray is rotated by electrostatic force or electromagnetic force to change the propagation direction of the input light, thereby realizing the on and off function of the light path.

Generally speaking, MEMS based optical switch can be divided into two types in terms of spatial structure: 2D switches and 3D switches.

(a) 2-D (b) 3-D Source: researchgate.net

The rotating mirror of the 2D MEMS optical switch is monolithically integrated on the silicon substrate through surface micromechanical manufacturing technology, and the collimated light is connected to the designated output terminal through the rotation control of the micro mirror. When the micro mirror is horizontal, the light beam can pass through the micro mirror. When the micro mirror rotates perpendicular to the silicon substrate, it will reflect the light beam incident on its surface, so that the light beam can pass through the corresponding output port of the micro mirror. In the 3D MEMS optical switch, the micro mirror can rotate arbitrarily along two axes, so different angles can be used to change the output of the optical path. These arrays usually appear in pairs, and the input light reaches the first array mirror. It is reflected to the mirror surface of the second array, and then the light is reflected to the output port.

Structure of MEMS Fiber Optic Switch

Fiber optic switch is a multiport device. The port configurations include 2×2, 1×N, N×N. Optical switch with N×N ports is usually called OXC (optical cross connect). The structure of a MEMS-based 1×N optical switch is shown in Fig, which consists of a MEMS torsion mirror, a collimating lens and a multi-fiber pigtail. The MEMS mirror is usually assembled on a TO base, then the collimating lens is joint to the sub-assembly through the TO cap. Finally, the multi-fiber pigtail is actively aligned to the sub-assembly.

Structure of the 1×N MEMS optical switch

MEMS optical switch VS Mechanical optical 

The working principle of mechanical optical switches is to redirect optical signals by physically moving optical fibers with the help of mechanical equipment. By moving the prism or directional coupler, the light at the input end will be directed to the desired output port. There are three main types of mechanical optical switches: one is to use a prism to switch the optical path technology, the other is to use mirror switching technology, and the third is to switch the optical path by moving an optical fiber.

MEMS optical switches are based on micro-electro-mechanical systems, which use optical micro-mirrors or optical micro-mirror arrays to change the direction of light beams to switch optical paths. The principle of MEMS optical switches is very simple. When the light is exchanged, the angle of the MEMS micro-mirror is moved or changed by the drive of the electrostatic force or the magnetic force, and the input light is switched to the different output terminals of the optical switch to realize the switching and on-off of the optical path. 

The advantages of MEMS switch

The MEMS optical switch can realize the comprehensive remote control of the all-optical network, and has the main advantages of high integration, low power consumption and low cost. MEMS optical switches have the advantages of mechanical optical switches, such as low insertion loss, low crosstalk, low polarization sensitivity, high extinction ratio, high switching speed, small size and easy large-scale integration of waveguide switches. This will be the mainstream direction for the development of large-capacity switching optical network switches.

The applications of MEMS fiber optic switch

MEMS optical switches and the switch arrays have a wide range of applications in optical communications. Its application scope mainly includes: optical network protection switching system, light source control in optical fiber test, real-time monitoring system of network performance, optical device test, construction of switching core of OXC equipment, optical add/drop multiplexing, optical test, optical Sensing system, etc.

Applied in MCS (multicast switching optical switch)

MCS based on PLC technology and MEMS technology is a key component of the next generation reconfigurable optical add/drop multiplexing system (ROADM). Each functional unit is composed of M independent splitters and N independent MEMS optical switches, which provide connections from N upper (or lower) ports to M directions.

Applied in iODF (intelligent optical distribution)

Through optical switch cascade integration, it can be used in iODF to replace the traditional distribution frame in the industrial private network.

As the switching core of OXC (Optical Cross Connect) equipment

In the all-optical switching system, the optical switch is a key component of the OXC. Through optical switch cascade integration, it can be used in small OXC to meet the needs of industrial private networks and key lines in data centers.

Applied in optical performance monitoring

Integrated with TOF or OPM, combined with monitoring software, and through time division multiplexing OPM, it can be used to monitor the signal performance of the DWDM channel in the multi-core fiber in the optical cable. It is widely used in optical transmission network cable monitoring, ROADM network, DCI, etc.

Applied in optical cable monitoring

It is integrated with OTDR and combined with monitoring software to monitor the quality of multi-core optical fibers in the optical cable. It is widely used in PON network optical cable monitoring, optical transmission network optical cable monitoring, industry-specific network optical cable monitoring, etc.

Applied in optical fiber sensing

The main products used in Sensing field are 1x4 and 1x8 switch.

Applied in test instrumentation and factory automation

Applied in DWDM system

The MEMS based optical switch in AON

What is an all-optical network? AON is the abbreviation of All Optical Network, which means that the transmission and exchange process of the network is realized through optical fiber. This means that the data transmission process from the source node to the destination node is carried out in the optical domain, and the optical/electrical, electrical/optical conversion is only performed when entering and leaving the network. Since there is no need to implement electro-optical and photoelectric conversion, the network speed can be greatly increased. The main technologies of the all-optical network include optical fiber technology, SDH, WDM, optical switching technology, OXC, passive optical network technology and optical fiber amplifier technology.

Structure of AON

Among the various equipment of all-optical network, OXC and OADM (optical add-drop multiplexing equipment) are the core equipment technologies of all-optical network. Optical switches and optical switch arrays are the core technologies of OXC and OADM. The new optical switch made by MEMS technology is small in size, light in weight and low in energy consumption. It can be compatible with the manufacturing process of large-scale integrated circuits. It is easy to mass produce, integrate, and has low cost.

In recent years, as a MEMS optical switch manufacturer, HYC has focused on the research of large-channel multi-core fiber collimators, and has made achievements in the compact layout of high-density fibers. Now, we have the mass production capacity of 1×48 optical switches. HYC will officially release 1×64 MEMS optical switches or more channels.

HYC Showcases Hybrid Series Product at ECOC 2020 Virtual Event

 The European Optical Fiber Communication Exhibition ECOC is the largest optical fiber communication exhibition in Europe, which is held in EU countries every year. The event was originally scheduled to take place in Belgium in September, but due to the impact of the epidemic, it was rescheduled to take place online on December 7-9. HYC also participated in this virtual exhibition with the latest products and solutions. At the virtual exposition, visitors will have the opportunity to explore HYC’s high-density cabling solutions, micro-optic solutions, 5G Open-WDM solutions and more. 

In recent years, the integrated optical passive devices are smaller in size and more mature in technology, occupying a considerable part of the market share. As one of the key devices of optical communication, erbium-doped fiber amplifier (EDFA) has become the technical focus of competition among many manufacturers due to its integration, miniaturization, multi-function and low cost.  HYC has launched a series of customized small N in 1 integrated high-end devices that can be applied to ultra-small EDFAs to help realize the above-mentioned competitive advantages of EDFAs. The above competitive advantages of EDFA can be realized by integrating optical isolator, wavelength division multiplexing (WDM) devices, optical circulator and test access port (TAP) splitter into a hybrid device.

In addition to the above-mentioned Hybrid components, HYC also demonstrated full-band/dual-window/multimode/polarization-maintaining couplers, fiber optic circulators, MPO/MT-FA, AWG CWDM4 and other micro-optic solutions.

At this exhibition, HYC also highlighted the CEx wavelength coexistence WDM module used in the "Trip-play" network. The CEx WDM module is a transitional product in the evolution of PON technology.  At present, the main PON technologies can be divided into three types: TDM-PON, WDM-PON and OFDM-PON. The original proposal of CEx wavelength coexistence is mainly to allow G/EPON to realize system sharing with NG-PON1 and NG-PON2, so as to achieve a smooth upgrade and save costs.

For 400G transmission applications, HYC is also actively exploring new solutions, and has launched a series of AAWG products such as 50GHz 96CH AAWG and 75GHz 64CH AAWG. Arrayed waveguide gratings (AWGs) are key components of DWDM (Dense Wavelength Division Multiplexing Systems) networks that are rapidly developing. The AWG can obtain a large number of wavelengths and channel numbers, realize multiplexing and de-multiplexing of tens to hundreds of wavelengths, and can flexibly form multifunctional devices and modules with other optical devices. High stability and excellent cost performance are also one of the reasons why AWG has become the technology of choice for DWDM. Based on the array waveguide grating technology, it does not require additional power supply or temperature control, and is a pure passive module. The application of AAWG can greatly improve the propagation efficiency of optical fiber networks.

ECOC's online exhibition will be open until January 15. Customers from all over the world are welcome to visit HYC's online virtual booth to explore new technologies and directions in the optical communications industry.

About HYC Co., Ltd

HYC focuses on the design, development, manufacturing and sales of optical passive basic devices for optical communications, providing customers with one-stop product procurement and customized services. The production and sales of products include optical fiber connectors (high-density optical connection products for data centers), WDM wavelength division multiplexers, PLC optical splitters, MEMS optical switches, etc., and continue to explore new product areas, including Hybrid combination devices, optical fiber circulator and other Micro-optic device products. For details, please visit www.hyc-system.com

 OTDR is an Optical Time-domain Reflectometer. It is the main devices in optical fiber measurement. It uses to test detect problems that may exist in fiber links.

OTDR is widely used in carrier backbone networks. By analyzing the measurement curve, it can quickly detect the fault location of the optical fiber link and the fiber loss. The working principle is to use a laser light to send a higher power laser or light pulse to the test fiber. OTDR observes the power of the laser signal from each point on the fiber and records these results through a trace diagram. It can calculate the distance by recording the return time and transmission speed. 

In the PON (Passive Optical Network) network, especially the complex point-to-multipoint PON ODN (Optical Distribution Network) topology applications, rapid monitoring, and diagnosis of fiber fault locations is a challenging subject. At present, optical time-domain reflectometer (OTDR) tools are widely used for monitoring the fiber network. However, OTDR detection may not be so particularly sensitive to the attenuation of optical signals at the ends of some ODN branch fibers or ONU fibers. The application of FTTx terminal splitter to the main cable signal makes the traditional OTDR fiber optical detection techniques unable to achieve on-off detection. So a cost-effective and wavelength selective fiber optic reflector is a basic method of implementation of optical layer monitoring on the whole length of an FTTx network from the OLT to the ONT in real-time.

The working principle of the fiber optic reflector is mainly to use Fiber Bragg Grating (FBG) to reflect the test light pulse sent by OTDR with nearly 100% reflectivity. But the wavelength of normal passive optical network (PON) will pass with a small attenuation. The main purpose is to accurately calculate the return loss value of the reflected event at the end of each ONU branch by detecting whether the reflected OTDR test signal exists and the intensity of the optical signal. Therefore, it can easy to determine whether the optical link from the OLT side to the ONU side is normal. By detecting the reflected signal through OTDR, it can accurately grasp the fiber breakage, loss anomalies, fault location, and locate the error quickly.

The end-to-end OTDR measurement from the OLT to the ONT is usually difficult because the splitter brings high losses and complex networks. The application of optical fiber reflector is a cost-effective solution to help OTDR detection, and is the best way to realize real-time end-to-end (OLT to ONT) monitoring of optical networks in FTTx networks.

The optical fiber (FBG) reflector independently developed by HYC has the advantages of low insertion loss, high reflectivity, and convenient installation. It is widely used in PON network, OTDR testing, central computer room testing, FTTX and other fields. HYC offers customized pigtail or adapter type, such as LC, SC, APC/PC and so on.

HYC provides optical passive components OEM/ODM services. We welcome any inquiry for customized optical devices solutions for optical communication industry, including fiber optic connectors/adapters, WDM, PLC splitter, MEMS optical switch for data center, FTTx, Cloud Computing industry, 4G/5G networks .

Mechanical Optical Switch & MEMS Optical Switch

 In the optical fiber communication system, the optical switch (OS) is mainly used to realize the physical switching of optical signals or other logical operations in the optical path, and is mostly used in the optical cross-connect (OXC) technology as a key device for optical switching.

Optical switch is a multiport device. The port configurations include 2×2, 1×N, M×N. Optical switches have a wide range of applications in optical fiber communication systems. According to the realization technology can be classified as mechanical optical switch, thermo-optical switches, acoustic-optical switches, electro-optical switches, magneto-optical switches, liquid crystal optical switches and MEMS optical switches, etc. Mechanical optical switch and MEMS optical switch are the two widely used optical switches.

The working principle of the mechanical optical switch is to redirect the optical signal by physically moving the optical fiber with the aid of a mechanical device. By moving the prism or directional coupler, the light at the input end is directed to the desired output port. There are three main types of mechanical optical switches: one is to use prism to switch the optical path technology, the other is to use mirror switching technology, and the third is to switch the optical path by moving optical fibers.

Mechanical optical switch

The MEMS optical switch is based on a micro-electro-mechanical system, which uses an optical micro-mirror or an optical micro-mirror array to change the direction of the beam to switch the light path. The principle of the MEMS optical switch is very simple. When the light is exchanged, the angle of the MEMS micro mirror is moved or changed by the drive of electrostatic force or magnetic power, and the input light is switched to the different output terminals of the optical switch to realize the switching and on-off of the optical path. The schematic diagram is shown below:

The principle of mems optical switch

The principle of the 2×2 optical switch is shown in Fig. Four waveguides are aligned in four directions and a vertical MEMS mirror is aligned in 45° direction. When the mirror is not inserted into the optical path, optical beams from waveguides 1 and 2 are coupled to waveguides 3 and 4, respectively. The port connection is 1→3 & 2→4, which is the bar state. When the mirror is inserted into the optical path, optical beams from waveguides 1 and 2 are reflected by the mirror and then coupled to waveguides 4 and 3, respectively. The port connection is switched to 1→4 & 2→3, which is the cross state.

Principle of the 2×2 MEMS optical switch, left: bar state, right: cross state

MEMS optical switch

With the rapid development of optical communications, the status of optical interconnection and optical switching as optical network nodes is becoming more and more important, and the application of optical switches is becoming more and more extensive. MEMS optical switches have the advantages of compactness, fast switching speed, and easy expansion. At the same time, they have the low insertion loss, low crosstalk, low polarization sensitivity, high extinction ratio and high switching speed of waveguide switches, small size, and easy expansion of mechanical optical switches. The advantages of large-scale integration. It will be the mainstream direction of the development of high-capacity switching optical network switches.

HYC independently develops MEMS optical switch series products, with 1×2, 1×4, 1×N channel configuration, which can be expanded up to 1×48 channels, and has the advantages of low power consumption, integration, fast response speed, and cost reduction. Headquartered of HYC Co., Ltd is in Qingyuan Guangdong, and HYC has R&D centers in Wuhan and Shenzhen. It has more than 1,000 employees and has more than 20 years of OEM and ODM experience. It provides one-stop customization for the design, R&D and manufacturing of optical communication optical passive components. 

How to choose the high-density fiber optic patch panel

 The fiber optic patch panel help manage the termination of optical fiber cables. It is mainly used for the cross-connection of optical cables, management of optical fiber jumpers, and the integration of optical fiber fusion splicing, optical fiber terminals, optical fiber adapters and cable connectors.

The optical fiber distribution box has many specifications, the common ones are rack type and wall box type. The 19-inch standard rack type, in U or RU as the unit, refers to the height of the equipment to be installed in the rack, and usually has a size of 1RU, 2RU, 4RU. It has a slide-out and sliding drawer design, which not only allows flexibly cabling but also protects optical fibers. It is an ideal cabling management solution for data centers.

When the requirement of fiber high-density increases, how to effectively manage and organize a large number of patch cords becomes extremely important. A good fiber distribution box will need to have the function of easy management of patch cord replacement. 

HYC’s uniquely designed high-density fiber patch panel is suitable for standard 19" rack installation. It adopts environmentally friendly, high-strength lightweight materials and excellent surface treatment technology. Each layer is an independent drawer type plug-in cassette controlled by smart spring cotter achieve easy inserting and pulling. Independent cable management frame design at the rear of the panel is easy for fixing the trunk cable. The redundant trunk cable ensure the cassette move properly. And a clear and organized panel pocket label convenient for independent label printing and replacement.

The optical fiber distribution box will take up valuable cabinet space. How to design a space-saving distribution box without affecting the organization and management of the optical fiber system is of great significance. This fiber optic patch panel can be uploaded with maximum LC connecting and cabling. 1U can be loaded with 6 pcs cassettes with 144-core LC or 72-core SC connectors, 2U can be loaded with 12 pcs cassettes with 288-core LC or 144-core SC connectors, 4U can be loaded with 24 pcs cassettes with 576-cores Or 288 core SC connectors. The connections in the cassette can be customized according to application requirements, such as MPO-LC, PLC-LC, WDM-LC, etc.

The fiber optic patch panel is an important equipment in the optical network transmission process, which can effectively achieve the termination, protection and management of the optical cable. HYC based in china focuses on development and production of optical passive devices, and strive to offer a variety of customized fiber optic patch panels according to customer's requirements. HYC has 20 years of experience in the optical communications industry, has a strong R&D team and manufacturing capabilities, and can provide customers with one-stop production customization services. The product line includes optical fiber connectors, optical fiber jumpers, PLC optical splitters, and WDM Wavelength division multiplexer, MEMS optical switch, etc.

What is LWDM (Lan Wavelength Division Multiplexing)

 There are CWDM(coarse wavelength division multiplexing),DWDM(dense wavelength division multiplexing),and newly MWDM,LWDM in 5G WDM bearer solutions. MWDM and LWDM are two kinds of WDM proposals presented by China Mobile and China Telecom. MWDM reuses the first 6 waves of CWDM, compresses the wavelength interval to 7nm, and expands it to 12 waves with a 3.5nm offset.

And LWDM is based on the Ethernet channel wavelength division multiplexing Lan-WDM technology, also known as dense wavelength division multiplexing. Its channel interval is 200~800GHz, this range is between DWDM (100GHz, 50GHz) and CWDM (about 3THz). LWDM uses 12 wavelengths in the O-band range from 1269nm to 1332nm, with a wavelength interval of 4nm (Wavelengths including 1269.23, 1273.54, 1277.89, 1282.26, 1286.66, 1291.1, 1295.56, 1300.05, 1304.58, 1309.14, 1313.73 , 1318.35nm).

 

The characteristic of LWDM working wavelength is that it is located near zero dispersion, with small dispersion and good stability. At the same time, LWDM can support 12-wave 25G to increase the capacity and save fiber. 

HYC can provide customers with a full range of WDM solutions, including the latest MWDM, LWDM and CWDM, DWDM products. HYC has 20 years of OEM/ODM manufacturing experience in the optical communication industry, and has a certain influence in the global industry. It focuses on providing customers with one-stop customization of the design, development and manufacturing of passive basic optical components for optical communication. The production lines includes fiber optic connectors, fiber optic jumpers, PLC splitters, WDM wavelength division multiplexers, MEMS optical switches, and so on. Products are widely used in FTTH, data centers, 5G networks, and telecommunication networks.

Simplex & Duplex Fiber Optic Patch Cord

 The fiber optic patch cord can be divided into two types according to the work mode of the interface, it is simplex and duplex. Then what is simplex and duplex, how to use them? They are two kinds of communication channels in telecommunications and computer networking, which provide pathways to convey information.

What is simplex fiber patch cord?

Simplex is that data transmission only supports transmission in one direction. The two ends of communication, one end is the transmitter and the other end is the receiver, which is not reversible. For example, broadcasting stations usually only send signals to audience site, and do not receive signals from audience site.

 

What is duplex fiber patch cord?

Duplex is divided into half duplex and full duplex. Half-duplex can transmit data in both directions on the signal carrier, but not at the same time. In the communication process, the transmitter and receiver at both ends of the communication system can switch the direction through the receive/transmit switch to realize transmission in a single direction. It can also be said that the half-duplex mode is a simplex communication with switchable directions. . For example, on walkie-talkie, when you press the call button, you can send a conversation to the other party, and the other party can also hear it, but the other party cannot talk to you at the same time.

Full duplex is capable of two-way data transmission in both directions of the signal carrier at the same time. Receiving data while sending data, which requires the sending end and the receiving end to have independent receiving and sending capabilities at the same time. The full-duplex mode can also be seen as a simplex communication that allows two-way simultaneous transmission. Just like a telephone, both parties can talk at the same time by using two-way instant transmission technology. The duplex jumper can be composed of two simplex jumpers through a special design. For example, the Uniboot jumper uses a single tube and dual core.

Both simplex and duplex fiber jumpers can have single-mode and multi-mode modes. Single-mode and multi-mode have different applications. Generally speaking, single-mode is compared Suitable for long-distance transmission, and multi-mode is suitable for short-distance transmission. Choose which mode of fiber jumper depends on the actual applications.

HYC has focused on the OEM/ODM manufacturing of passive optical communication devices for 20 years. It has a strong R&D team and production capacity, and can provide customers with one-stop customized production of optical communication passive basic device design, R&D and manufacturing. The production lines mainly include fiber optic connectors, fiber jumpers, PLC splitters, WDM wavelength division multiplexers, MEMS optical switches, etc.