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.
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.
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.
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.
The development of 5G networks starting in 2019 is generally believed to bring changes not limited to people’s daily life. It will support the evolution of Internet from mobile internet to intelligent internet, which will influence the industrial-ecology deeply.
The international standard organization 3GPP defined the three main application scenarios of 5G: eMBB (Enhance Mobile Broadband), uRLLC (Ultra-Reliable Low Latency Communications), mMTC (Massive Machine Type Communication). eMBB requires the bandwidth experienced by the customers to be more than 1Gbps supporting mobile broadband surfaces such as 3D and ultra-high definition video. uRLLC requires the transmitting delay to be <1ms supporting real time applications such as self-driving cars, industrial automation, and remote surgery. mMTC means application in massive internet of things (IOT) which requires high density terminal connection of more than one million per square kilometer.
Structure of the 5G Carrying Network Build the carrying network before commercial application of 5G. In order to support the aforementioned three application scenarios, the carrying network based on optical fiber is required to be reconstructed. Fig.1 shows a typical structure for 5G carrying network, which usually consists of metro access network, metro aggregation network, metro core network and inter-province backbone network. Considering investigation and operating cost, the radio access network (RAN) of 4G usually employs D-RAN (distributed wireless access) structure based on function division of RRU+BBU, while the 5G system employs C-RAN (centralized or clouded wireless access) structure based on function division of AAU+DU+CU.
Fig.1 Structure of 5G carrying network
The interconnection between the nodes of 5G carrying network is realized through optical transceiver modules and optical fibers. The interconnection between the wireless base station and DU is defined as front-haul. The interconnection between DU and CU is defined as mid-haul. The interconnection between CU and the metro core network is defined as back-haul. The front-haul distance is usually <10/20km and the bit rate of the data interface is 10/25/100Gbps. The mid-haul distance is usually <40km and the bit rate is 25/50/100Gbps. The back-haul distance is usually 40-80km and the bit rate is usually 100/N×100Gbps. The transmitting span of the trans-provincial backbone network is usually hundreds of kilometers and the bit rate is N×100/200/400Gbps.
Fig.2 The front-haul, mid-haul and back-haul link of the 5G carrying network
Comparing to the 4G network, the frequency of 5G signal is higher and thus the coverage of a single base station is less. Thus the base stations needed by 5G network is 2-3 times of those by 4G network. C-RAN structure is preferred in the front-haul and mid-haul of 5G network, instead of D-RAN in 4G. There are mainly three advantages for C-RAN. Firstly, the required number of terminal equipment rooms and transmitting equipments is reduced. Thus the cost for station address acquisition, equipment room renting, and data transmission is reduced. Theoretically, the more is the DUs concentrated, the cost down is more. Secondly, the concentrated deployment of DUs facilitates the maintenance. Thus the cost for equipment room construction, equipment maintenance, and power rate is much lower than D-RAN. Thus C-RAN is regarded as the main deployment mode of 5G front-haul network. Thirdly, the DUs are grouped and deployed in a DU pool, or in clouded deployment. Thus the baseband resources can be shared and service cooperation between stations is realized.
Consideration for the Choice of Transmitting Technologies Optical fiber transmission is widely employed in telecom backbone network and data centers. In order to improve the transmission capacity, WDM technologies are commonly used. However, the concrete transmission technologies are diverse facing different application scenarios. The main factors influencing the choice are power loss and chromatic dispersion of the fiber link. The laser sources (with modulators included) and photon detectors (PDs) are important for the cost of the transmission system and should be considered in choice of proposals. What’s more, the heritage of industrial chain also influence the cost and is one of the factors to be considered.
The spectral transmission loss of the common quartz fiber is shown in Fig.3. Its first, second and third transmission windows are centered at 850nm, 1310nm and 1550nm. 850nm is the wavelength selected by the first multimode fiber (MMF) communication system. 1310nm is the zero dispersion wavelength of the conventional single mode fiber (SMF) G.652. As shown in Fig.4(a), the material dispersion and waveguide dispersion counteracts at this wavelength. 1550nm is the wavelength experiencing the lowest loss for quartz fiber. G.655 SMF was developed with its zero dispersion wavelength set with a small shift from 1550nm, as shown in Fig.4(b). Thus low dispersion is obtained at 1550nm-band and non-linear effects, such as four-wave mixing and cross-phase modulation, are avoided.
Fig.3 Spectral transmission loss of quartz fiberFig.4 Spectral dispersion of G.652 and G.655 optical fibers
In the engineering applications, the second and third windows in Fig.3 are usually called O-band and C-band, respectively. In order to extend the available transmission band, S-band and L-band are developed neighboring to C-band. What’s more, the water peak around 1385nm (due to OH- absorption) is cut down by further purification of quartz fiber. Thus E-band is developed and the transmission band of quartz fiber is extended to 1260~1620nm. The bandwidth is totally 360nm and the optical fiber is called all-wave fiber.
The optical fiber communication system usually employs semi-conductor lasers as the light source. The emission from a semi-conductor laser is not an ideal monochromatic light. It has a certain linewidth. The different wavelength components transmit in different velocity due to dispersion and thus bit error is introduced in high-speed, long-haul transmission system. Optical signals in different bit rate have different dispersion tolerance, as shown in Table 1.
Table 1. Dispersion tolerance for optical signals in different bit rate
The early transmission system in low bit rate usually employ FP lasers with low cost and broader linewidth. However, DFB lasers are necessary for high-speed transmission systems with bit rate ≥10Gbps. When the transmission distance is not too much, people intend to modulate the DFB lasers directly, which are called DML (Direct Modulated Laser) lasers. Direct modulation on the lasers generates chirp effect and broadens the linewidth, which introduces more chromatic dispersion. In order to avoid broadening the linewidth of the lasers to transmit longer distance, external modulation is employed. An EAM (Electro-absorption Modulation) modulator is cascaded behind the laser. The DFB+EAM combination is called EML laser. In order to transmit ever longer distance, LN (Lithium Niobate) modulator is required, which is an electro-optical modulator with Math-Zehnder (MZ) interferometer structure.
Transmission Proposal for Different Application Scenarios The focus of 5G investment is development of the front-haul and mid-haul networks. The investment is too much and exceeds the affordability of a single telecom operator. China Unicom and China Telecom decide to develop a 5G front-haul network together, while China Mobile cooperates with China Radio and television network Cooperation. A wireless base station should be equipped with upload/download interfaces for three sectors. Under the co-construction and sharing mode, the bandwidth demand for a single base station is doubled and thus six 25G interfaces are required for a 5G base station. For the deployment scenario where 4G and 5G equipments share a base station, 12 front-haul interfaces are required. In some multi-service access region, bandwidth demand is much higher and 24 front-haul interfaces are required for a single base station. Based on above application scenarios, base stations with 12 interfaces will become the main-stream construction in the 5G front-haul network.
In the 4G front-haul network, BBU is set near to RRU and D-RAN configuration is more adopted. The mostly employed transmission proposal is fiber direct driving. While in the 5G front-haul network, DU is deployed far from AAU. The cost of optical fiber is too much and thus xWDM is popular to save fiber resources. According to the application scenarios and based on the deployed fiber resources, the configurations of 5G front-haul networks can be D-RAN, C-RAN small aggregation and C-RAN massive aggregation, as shown in Fig.5. In the D-RAN deployment, fiber direct driving proposal is selected. BiDi (bi-directional transmission in and single fiber) transmission is suggested to save half of the fiber resources, as shown in Fig.6. In C-RAN small aggregation deployment, six 25G interfaces are required and 6-λ CWDM transmission is proposed, as shown in Fig.7.
Fig.5 The deployment configurations of 5G front-haul networkFig. 6 Fiber direct driving proposal for front-haul networkFig.7 6-λ CWDM proposal for 5G front-haul network
In C-RAN massive aggregation deployment, each wireless base station requires 12 high-speed optical interfaces. China Mobile presented a 12-λ MWDM proposal. The 12 wavelengths are listed in Table 2. Based on the 6-λ CWDM laser chips, the emission wavelengths are shifted by 3.5nm to the left and right through TEC tuning. Thus 12 wavelengths are obtained based on the current industrial chain for data transmission. China Telecom selected the 12-λ LWDM proposal. The channel spacing is 800GHz. The 12 wavelengths are listed in Table 3. TEC is required to stabilize the emission wavelength of the laser sources because the wavelength pitch is only 4.3-4.7nm. The power consumption of the optical transceiver module is about 0.5W higher due to the introduction of TEC module.
Table 2. CWDM/MWDMtransmission wavelengths and proposalsTable 3. LWDM transmission wavelengths and proposals
The different WDM wavelengths and dispersion spectrum of quartz are shown in Fig.8. The latter two wavelengths of 6-λ CWDM is far from the zero-dispersion wavelength 1310nm. In order to compensate for the power loss cost due to dispersion, APD photon detectors are employed which have higher sensitivity. Thus we can see, for the CWDM transmission proposal in Table 2, the laser sources and PDs choose DML+PIN for the former wavelengths, while DML+APD for the latter two wavelengths. For the same reason, the latter four wavelengths of MWDM also employ DML+APD.
Fig. 8 Chromatic dispersion spectrum of optical fiber and WDM proposals for 5G front-haul network
Table 2 and 3 list different WDM transmission proposals for 5G front-haul network, together with the sharing of the current industrial chain in data transmission (for data centers). WDM technologies were first applied in telecom mainly for long-haul transmission in the backbone networks and core networks. DWDM transmission in C-band (1530-1570nm) is preferred because the transmission loss of quartz fiber is the lowest at this band. However, the optical devices for this industrial chain are expensive. With the development of mobile internet and the construction of massive data centers, optical fiber transmission technologies are widely employed, which become the second and ever larger blue-ocean market of optical fiber communication technologies. The transmission distance in data centers are relatively short (comparing to telecom applications), while the data transmission speed is higher. The aim of transmission proposals is focused on solution of dispersion restrictions, which is different from loss restriction in telecom long-haul network.
The current 5G front-haul network is part of the telecom network, while its application scenarios are different from those of telecom long-haul network. It is similar to the applications in data centers. The transmission is characterized by high-speed and short distance, which is mainly restricted by chromatic dispersion. Thus the transmission wavelengths are selected in O-band centered at 1310nm. CWDM4, LWDM transmissions in O-band have been widely deployed in data centers. The industrial chains are mature and the cost is low. 5G front-haul network can share its industrial chain to cut down the investment. For example, for the 6-λ CWDM proposal in 5G front-haul network, the former 4 wavelengths can share the CWDM4 industrial chain of data transmission. For the 12-λ MWDM proposal, the former 8 wavelengths can also share the CWDM4 industrial chain. For the 12-λ LWDM proposal, the 2-5 wavelengths can share the 400G LR8 industrial chain and the 7-10 wavelengths can share the 100G LR4 industrial chain.
Sharing the CWDM4 industrial chain for data transmission is one of the main considerations why China Mobile projected MWDM proposal. The construction of 5G network can be started as soon as possible with the cost under control.
In response to the new needs of 5G fronthaul applications, HYC quickly launched MWDM and LWDM series products to make full use of O-band optical resources, increase band utilization, and increase speed. HYC can provide customers with a full range of WDM wavelength division multiplexing solutions, including CWDM, DWDM, CCWDM, MWDM, LWDM products, etc.
HYC Co., Ltd has 20 years of R&D and 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, R&D and manufacturing of passive optical devices. HYC has production lines including fiber optic connectors, patch cords, 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.
The secure lockable fiber optic connector is mainly used in some private networks with high security level requirements, and improves security by preventing unauthorized modifications in the entire critical network.
The MPO secure lockable connector is a secure accessory that can be compatible with conventional MPO connector. Once the MPO connector with secure accessory insert into the adapter, it will be locked. The connector cannot be pulled out unless remove the secure accessory. MPO connectors equipped with safety locks will not affect the original height and density of the connectors, and are also compatible with conventional adapters and optical modules. The installation is simple and convenient, requires no extra tools. It can effectively prevent releasing the connector by mistake, and to reduce the chance of getting dusty on the connector's surface.
SC secure lockable connector is designed with unique keying details in the connector body, as long as it is inserted into the adapter, it is locked and the connector cannot be pulled out. The connectors of different colors correspond to the keys of the same color to open the lock and pull out the connector. There are also dust caps with locks that are suitable for SC conventional adapters, which can prevent dust and lock. For some unused fiber ports, it can prevent mistaken insertion.
LC keyed connector is installed with a secure lock accessory on the LC duplex connector. The connector with lock accessory can be locked once insert into the adapter. You need to use the equipped unlocking key to pull out the connector. There is also a dust cap with lock for the LC adapter, which can be unlocked with the same key. Removing the security lock accessory on the connector will not interfere with the LC adapter or cause network performance degradation.
HYC Co., Ltd was founded in 2000, has 20 years experiences in OEM ODM manufacturing of passive optical devices. We focus on providing customers one-stop services of the design, R&D and manufacturing of passive optical communication devices. We have fiber optic connectors, fiber optic jumpers, WDM wavelength division multiplexing, PLC optical splitters, MEMS optical switches and other product lines.
As we all know, too little or too little optical power will cause equipment errors. Too much power will saturate the receiving amplifier, while too little power will interfere with the signal and cause noise problems. An optical fiber attenuator is an optical device that can be used to attenuate the input power to avoid distortion of the optical receiver due to excessive power.
The optical fiber attenuator reduces the optical power through the absorption, reflection, diffusion, scattering, deflection, diffraction and dispersion. How to reduce the power light level? The fiber attenuator is set in a working wavelength range that can absorb light energy. Within this range, it will not reflect light and reduce unnecessary echo reflection. In this way, the optical power attenuation effect is achieved. Usually, the optical attenuator is made by air isolation technology, displacement dislocation technology, attenuation fiber technology, absorption glass method, etc.
The normally attenuation range of the optical attenuator is 0~65dB. The attenuation power of the fixed attenuators on the market is between 1 and 30dB. Fixed fiber attenuator is a type of fiber attenuator, which fixes the attenuation power at an attenuation value. It is commonly used in telecommunication networks, fiber optic test equipment, local area networks (LAN) and cable television (CATV) systems.
There is also a variable optical attenuator. The attenuation level of the variable attenuator can be adjusted, for example, from 0.5 dB to 20 dB, or even 50 dB. Some variable attenuators have very fine resolution, such as 0.1dB or even 0.01dB. Mainly used in: optical distribution frame, optical fiber network system, high-speed optical fiber transmission system, cable television (CATV) system, long-distance trunk line dense wavelength division multiplexing (DWDM) system, optical add/drop multiplexer (OADM).
Among them, the fixed optical attenuator has pigtail type, converter type and so on. It can be made into FC, SC, ST, LC, MU and other interface types, which is convenient to use in daily cabling. Generally, a single optical attenuator has two interfaces, male and female, which can be male-female or female-female. The male connector interface is generally used to plug into the receiver of the device or the adapter on the adapter panel, and the female connector interface is used to connect the fiber jumper. HYC can provide various types of fixed female and male optical fiber attenuators with stable performance and reliable quality, which can meet the requirements of various connector interface types and working wavelength customization of ST, SC, FC, MU, and LC.
Fiber optic attenuators are widely used in optical passive devices. The performance indicators to measure the optical attenuator mainly include attenuation, insertion loss, and attenuation accuracy, return loss, etc. High-performance optical attenuators have low insertion loss, and return loss is usually above 40dB.
HYC Co., Ltd was founded in 2000, has 20 years experiences in OEM ODM manufacturing of passive optical devices. We focus on providing customers one-stop services of the design, R&D and manufacturing of passive optical communication devices. We have fiber optic connectors, fiber optic jumpers, WDM wavelength division multiplexing, PLC optical splitters, MEMS optical switches and other product lines.
