Optical splitter is the core of FTTH optical device. It has great growth potential and will become the main driver of FTTX market growth. It will undoubtedly bring vitality and challenges to optical communication manufacturing industry, and also to optical communication enterprises. Bring another space for rapid development. This paper reviews the market status of PLC splitter, industry situation and technology development. The development of PLC chip, fiber array and coupling packaging technology was analyzed.
1 IntroductionAt present, the construction of China's FTTx (Fiber Access Network) is gradually unfolding. The three major operators and the broadcasting and television system have all defined the idea of ​​“accelerating the optical retreat and retreating and promoting the strategic transformation of the access network†to realize FTTC (optical fiber to the roadside). Multimedia transmission such as FTTB (Fiber to the Building), FTTH (Fiber to the Home), FTTD (Fiber to the Desktop), triple play (voice network, data network, cable TV network) and PDS (Integrated Cabling System) solution. In order to build an all-fiber network, in addition to the need for a variety of structural distribution cables, the introduction of fiber optic cables to achieve the connection and redistribution of fiber networks, in E-PON, G-PON technology, a large number of optical splitters are needed to finalize Fiber-to-the-home purpose.
The FTTx system consists of three parts: the central office equipment (OLT), the user terminal equipment (ONU), and the optical distribution network (ODN). As an important part of the FTTx system, ODN is the optical transmission physical channel between the OLT and the ONU. It is usually composed of fiber optic cables, optical connectors, optical splitters, and associated equipment for connecting these devices. From the ODF rack of the central office room to the feeder section of the cable distribution point, as the trunk optical cable, to achieve long-distance coverage; from the distribution point of the optical cable to the wiring section of the user access point, the nearest optical fiber is allocated to the user area along the feeder cable. The user access point to the terminal's home segment is completed by the butterfly-introduced optical cable, and all the branch and contact connections are completed by the optical splitter and the fiber is put into the household.
Optical splitter is the core of FTTH optical device. It has great growth potential and will become the main driver of FTTX market growth. It will undoubtedly bring vitality and challenges to optical communication manufacturing industry, and also to optical communication enterprises. Bring another space for rapid development. According to the arrival of the construction boom of the access network, from the current stage of the market and the development trend of future demand, PLC optical splitter will become the main force of the PON market. It is digital, networked, broadband, miniaturized and easy to maintain. Features are the focus of future market demand.
2. PLC (optical splitter) market and industry situation2.1 PLC (optical splitter) market situation
PLC (optical splitter) is mainly used in the access network passive optical network (PON), so that the central office is connected with multiple users to achieve fiber to the home. In 2008, the global demand was about 24 million channels, with total sales of 110 million US dollars and an average of 4.6 US dollars. The global market is different in different regions. After years of rapid development in Japan and South Korea, the number of demand has stabilized, but it still accounts for half of the market share, and North America has a market share of 30%. The FTTH of developing countries such as China, India and Brazil has just begun construction and will become the main growth point of the market.
In 2009, China's optical device market demand was strong, especially since the second quarter, sales revenue continued to grow for three consecutive quarters. In terms of products, 10G optical modules and PLC products performed well and the growth was strong. In the first and second quarters of 2010, domestic passive component manufacturers received good orders, and the market demand reached about 600 million yuan, a year-on-year increase of 16%. Driven by the accelerated deployment of FTTX by operators, the domestic PLC device market continued its strong growth in 2009, and demand for PLC splitters and AWGs was strong. At present, the market demand for passive components such as fiber connectors, couplers, isolators and attenuators has maintained steady growth, but prices have continued to decline due to further market competition.
In terms of operators, the three major operators have clearly required all PLC-type optical splitters in the FTTX network. From 2009 to 2010, China Telecom and China Unicom have been collecting tenders for PLC splitters for two consecutive years. In 2010, China Mobile has also begun to collect all equipment including GPON splitters used by GPON. Mining.
If the optical device market growth in 2009 is a 3G factor, then the growth factor in 2010 will be the FTTX factor. Although China's large-scale deployment of FTTX networks still has many obstacles, the government's decision to promote triple-play integration will bring strong power to FTTX, and the optical device market will also benefit. In the first half of 2010, under the promotion of operators' active FTTH construction and 3G network construction, and on January 13, 2010, Premier Wen Jiabao presided over the State Council executive meeting and decided to accelerate the integration of telecommunications network, radio and television network and Internet. This indicates that the government will begin to promote the deployment of FTTX networks, and the optical device market will benefit. According to ICCSZ forecast, the domestic optical device market will maintain steady growth in 2010. The domestic passive device market maintained rapid growth in sales. In the second quarter, domestic passive device sales were approximately 700 million yuan, a year-on-year increase of 17.8%. In the second quarter, the state issued the "Opinions on Promoting the Construction of Fiber Broadband Networks" to accelerate the construction of fiber-optic broadband networks; at present, the pilot program for triple-play integration has also been adopted. These factors have effectively promoted the further growth of optical device market demand, and also brought a large number of orders for passive device manufacturers. At present, the domestic FTTx network deployment process is accelerating. PLC products, as the core components of FTTX, will also receive a large number of applications. The demand for optical devices in China will reach 3.6 billion yuan, a year-on-year increase of 7.5%. It is expected that the optical device market in China will continue to grow in the second half of 2010.
Analysis of PLC Splitter Market Technology
2.2 PLC (optical splitter) industry situation
At present, China is already a major manufacturing country for PLC devices, and most of its products are produced in China and South Korea. There are about 100 optical splitter companies in China (including foreign-funded enterprises), and there are about 20 production and R&D capabilities. From China Telecom’s 2010 PLC collection information, nearly 100 enterprises across the country participated in the collection and bidding. ), including Fiberhome Communications, Wuhan Guangxun Technology, Bochuang Technology, Fuchuang Optoelectronics, Aokang Guangtong Devices, Wuxi Aifufu, Fuchunjiang Optoelectronics, Shenzhen Rihai Communications, Chengdu Feiyang Technology, Shanghai Shangcheng, Datang Communications (Kunshan), Nanjing Putian, Zhejiang Pusen and other enterprises into scale production, in addition to chip outsourcing, the other are produced by themselves. In addition, most companies have not formed a large climate in terms of product variety and production scale, and some enterprises basically buy the main body of the splitter, and then add the jumper head and shell assembly mode.
Analysis of PLC Splitter Market Technology
At present, all countries are vigorously promoting the engineering of FTTH and FTTx. With the in-depth development of FTTx (Fiber Access Network) in China, the demand for PLC splitter is obviously large, and PLC optical splitter may be the next passive device. The focus of market demand. In addition to the development of optical components and the increase in capacity, some well-known fiber optic cable manufacturers have also increased their investment in this area, actively developing passive device products, and are also adding production equipment, and this is The technical and product reserves, with its prepared and planned market share, can be seen in the market importance of PLC optical splitters in the next few years and the importance attached to this project by major optical device companies and fiber optic cable companies. However, the chip technology has not yet been mastered in China, and only chips can be purchased or packaged.
2.3 PLC (optical splitter) market price trend
In the future, China will occupy the dominant position in the PLC splitter market, and it is expected to occupy 35% of the market in three years. At present, the core technology chip of PLC-Splitter is also controlled by European, American and Japanese and Korean enterprises. Because there is no core technology, domestic enterprises can only develop Fiber Array to buy chips for packaging or directly to chip companies.
Everything has two sides. The increase in demand is always accompanied by the decline in product prices. As a large number of domestic device packaging companies flood into this market, plus three major operations to collect PLC optical splitters, market prices. It will face a downward trend. As demand continues to increase, prices will become lower and lower, and the profits of foundry companies and packaging companies will become thinner and thinner. Figure 1 shows the international price trend of PLC.
Analysis of PLC Splitter Market Technology
2.4 PLC (optical splitter) industry development problems
There are certain problems in the development of China's PLC optical splitter industry. Although the market demand is large, the expansion of production capacity and the potential risk of oversupply in the market are also rapidly increasing. First of all, due to the increasing pressure on manufacturing costs, especially for companies that only couple and package subsequent processes, the price of PLC optical splitter has dropped by about 40% compared with the beginning of 2008, and the current PLC splitter Relatively mature, with large-scale production, prices and gross margins will continue to fall, and the trend of market integration will become more apparent. The homogenization competition of the second domestic manufacturers, chips, V-shaped tanks and even FA all rely on imports, the cost pressure is very large. If the company is small, the cost pressure will be even greater, because the source of the material is mainly outsourcing, and the cost is inversely proportional to the purchase amount. If the purchase amount is small, the purchase price will be relatively high. It can be a difference of 20% to 30%. The third is the impact of WDM-PON on the PLC splitter. In addition to the EPON and GPON we often mention, there are WDM-PON. The evolution of next-generation fiber access technology is likely to be WDM-PON technology, and European and American countries are also more keen on this technology. However, from the technical point of view, the existing EPON multiplexing method is power split type, while WDM-PON belongs to wavelength division multiplexing, that is, the existing PLC splitter is not applicable to WDM-PON technology. If the process of this technology evolution is short, the current PLC splitter manufacturers will face serious challenges, and the equipment and capital input costs will be difficult to recover.
3. Development of PLC (optical splitter) technologyLow cost and high reliability are the basic requirements for optical branching devices in FTTH engineering. Optical communication optical splitters can be mainly divided into two types: optical fiber fusion taper type and planar integrated optical waveguide type.
The fiber fusion taper technology is the most mature technology for making 2 Ì2 optical splitter. The optical splitter is mainly based on all-fiber optical splitter. Its main features are: mature technology and convenient connection with optical fiber. The insertion loss is small. However, as the number of power splits increases, such as 1 & TImes; 8 or more optical power splitters are bulky, inefficient, high in cost, and poor in spectral uniformity. In addition, the characteristics of the fiber optic light splitter passband based on the fusion taper technology have great limitations.
PLC is based on integrated optics of planar technology. Different from the traditional discrete devices, he uses semiconductor technology to integrate optical components with different functions into one chip. It is the basic technology to realize the integration, scale and miniaturization of photovoltaic devices. Compared with the fused taper technology, the planar waveguide technology has remarkable features such as stable performance, low cost, and suitable for large-scale production. Therefore, fiber-optic melting cone optical power dividing devices will no longer be used in fiber-to-the-home systems, and planar waveguides provide an effective way for the production of high-performance, low-cost access optical devices.
3.1 PLC chip technology
PLC chips are generally fabricated on six materials, namely: lithium niobate (LiNbO3). The waveguide is formed by diffusing TI ions on a lithium niobate crystal to form a waveguide. The waveguide structure is a diffusion type; III-V semiconductor compound, waveguide InP is used as the bottom and lower cladding, InGaAsP is the core layer, InP or InP/air is the upper cladding, and the waveguide structure is buried ridge or ridge; SOI (Silicon-on-Insulator) The waveguide is fabricated on a SOI substrate. The bottom and bottom cladding layers, the core layer and the over cladding material are Si, SiO2, Si and air, respectively, and the waveguide structure is ridged and polymer (SiO2). , glass ion exchange, etc.
At present, there is no problem in fiber-to-the-home (FTTH) network technology, but whether it can be rapidly developed and popularized in China, in addition to policy, the most important and most important point is to reduce the cost of all aspects of the network. PLC optical splitter is one of the core devices in the FTTx network, and low cost is an important technical development goal. From the technical, cost and characteristics of the optical waveguide materials given in the above table, it can be seen that silica, polymer and glass are most suitable for making PLC chips. The following is a brief introduction to the three lowest cost, most industrially implemented PLC chip technologies:
(1) Polymer (spin coating - etching)
The polymer waveguide is based on a silicon wafer, and a polymer material having a different doping concentration is used as a core layer, and the waveguide structure is a buried rectangle. The polymer waveguide and device manufacturing process is simple and inexpensive, and if the photosensitive is better, the manufacturing cost is lower (theoretical value), and the development prospect is very promising. The problem is that the cost of fluorinated materials is high; the aging doubts and losses will be relatively high; the stability of the product should also be considered. At present, only Shanghai NITTA has the optical splitter product made by this chip.
(2) Silica
The silicon dioxide waveguide is based on a silicon wafer, and the different doped SiO2 material is used as a core layer and a cladding layer, and the waveguide structure is a buried rectangle. Silicon-based silica light wave technology is a new technology developed in the 1990s, and it has matured abroad. The manufacturing processes include flame hydrolysis (FHD), chemical vapor deposition (PECVD, developed by NEC Corporation of Japan), plasma CVD (developed by Lucent, USA), porous silicon oxidation, and melt-gel (Sol-gel). Wait. This waveguide and loss are small, about 0.05 dB/cm or less. 60-way and 132-way AWGs have been developed abroad using such waveguides. At present, flame-hydrolysis (FHD) and chemical vapor deposition (PECVD) are used to grow multilayer silicon dioxide materials, and dry etching is used to complete waveguide etching. The advantage is that it has very good physical and chemical stability technology, high device integration and low cost. At the same time, it has good compatibility with optical fiber, low transmission loss, mature technology (mainly dependent on the import of equipment), stable and reliable products, and theoretically, other PLC devices such as AWG can be produced. This process technology is currently the mainstream technology for the manufacture of chip products, and is generally adopted internationally. The problem is that the equipment investment is high, and the maintenance cost is high, and the raw material requirements are high (all imported materials are used); there are only a few research institutes and university experimental equipment online and Wuhan Guangxun Technology silica PLC process line in China, which are not available yet. Industrial scale production equipment. This technology and manufacturing are basically monopolized by foreign manufacturers such as Korea and Japan.
(3) Glass-based (ion exchange)
The glass waveguide forms a waveguide by diffusing Ag ions on the glass material, and the waveguide structure is of a diffusion type. The advantage is that the process is relatively simple, the equipment is relatively simple, the total investment is small, and the product is stable and reliable. The fabrication process of the glass optical waveguide is divided into five steps: 1) sputtering a layer of aluminum on the glass substrate as a mask layer during ion exchange; 2) performing photolithography to protect the desired waveguide pattern with photoresist 3) Remove the aluminum film on the upper part of the waveguide by chemical etching; 4) Place the glass substrate with the mask into a mixed solution containing Ag+-Na+ ions, perform ion exchange at an appropriate temperature, and increase Ag+ ions. The refractive index is obtained as a channel type optical waveguide; 5) an electric field is applied to the channel type optical waveguide, and Ag+ ions are driven deep into the glass substrate to obtain a buried glass optical waveguide. The main question of this technology: 1 Will it become the mainstream technology in the future, and some experts have doubts? 2 Because there is no large-scale commercialization and industrial production, the actual process stability of the product needs to be verified.
The above technical process is currently only produced in France by Teemphotonics Company of France and Colorchip Company of Israel. It is said that the original E-TeK company has this technology, but the specific details are unknown and cannot be verified. Professor Wang Minghua of the Department of Information and Electrical Engineering of Zhejiang University in China, a few years ago, began to cooperate with communication companies to develop a splitter based on glass ion-exchanged optical waveguides, and achieved certain results. Their advantage is that the key technologies are fully mature, all the raw materials need not be imported, the domestic can fully meet, and the optical splitter whose performance index reaches the level of similar foreign products has been developed, and all the intellectual property rights are their own. At present, commercial and industrialization technologies have not yet fully passed, and intermediate tests are needed, and various technical parameters are further improved. Therefore, from the perspective of industrialization, there is a considerable gap between PLC chip manufacturing technology and foreign countries. The process of technology practicalization and industrialization still needs a long way to go.
Analysis of PLC Splitter Market Technology
3.2 PLC fiber array technology
The output of the PLC splitter is coupled to each of the output optical waveguides in the PLC using an array of ribbons. Each fiber in the ribbon is positioned using a V-slot to ensure that all of the optical waveguides are automatically aligned with the ribbon once. The V-shaped groove substrate can be produced by a selective wet etching process from a single crystal silicon wafer, or can be fabricated by precision mechanical processing using a quartz glass plate.
Because Fiber Arrays are fabricated in V-grooves, special bonding processes are used to achieve precise fiber positioning and high reliability to meet different needs. The thermal expansion coefficient matching package design ensures that the fiber array board is stress-free, highly reliable, and has no fiber displacement at high temperatures. Therefore, high-precision V-grooves and highly reliable UV glue are key technologies in the fabrication of fiber arrays.
The matrix material of the fiber array product is quartz glass and heat-resistant glass, but it is generally made of quartz glass plate by precision machining. From the perspective of reliability, quartz glass is better, and it is not easy to crack when grinding. . The end face polishing angle can also be customized according to customer requirements, such as: 90 degrees, 98 degrees, 82 degrees, etc. The color and length of the fiber arrangement can also be customized according to customer needs.
Since fiber arrays are labor-intensive products, many foreign manufacturers have shifted their production links to China. At present, domestic companies that can develop and produce their own products include Bochuang Technology, Fuchuang Optoelectronics, Aokang Guangtong Devices, Dongguan Dongyuan and Zhejiang Tongtong. Stars, etc., mainly foreign companies are Japan's Hataken and AIDI companies. In the field of technology research and development and independent innovation, the development of domestic optical fiber array technology has also made breakthroughs, such as: high-precision U-shaped slot, using the etching process of independent intellectual property rights, this technology will be greatly reduced if it breaks through and becomes practical. The cost of fiber arrays. There are also square capillary arrays with excellent characteristics in AWG and single channel arrays.
Highly reliable UV glue is another key technology in making fiber arrays. The optical splitter manufacturing process has high requirements on the optical fiber array. In addition to the high precision of the V-shaped groove, the UV glue is required to have characteristics such as high temperature resistance, high humidity and sufficient hardness. At present, the series of composite products developed and produced by NTT-AT Corporation of Japan is the most advanced in technology, and the domestic technology is still blank.
3.3 PLC coupling and packaging technology
PLC optical splitter technology In addition to the chip and fiber array, another key technology is the coupling and packaging between the chip and the fiber. It involves the six-dimensional close alignment of the fiber array and the optical waveguide.
The PLC splitter package refers to aligning the respective light guiding paths (ie, waveguide paths) on the planar waveguide splitter with the optical fibers in the optical fiber array, and then bonding them with a specific glue (such as epoxy glue). A combination of technologies. The alignment accuracy of the PLC splitter and the fiber array is the key to this technology. The packaging process includes coupling alignment and bonding. The coupling of the PLC splitter chip to the fiber array is manual and automatic. The hardware they rely on mainly includes six-dimensional precision trimming, light source, power meter, microscopic observation system, etc., and the most common is automatic alignment. It forms closed-loop control through optical power feedback, so the docking accuracy and the coupling efficiency of docking are high. At present, the most advanced foreign coupling coupling equipment suppliers are: Japan's Suruga, Japan's Kuge, Newport, etc.; domestic development, but the six-dimensional accuracy can not meet the coupling requirements.
With the large increase in demand for optical splitters by FTTH, the domestic PLC device packaging industry has developed rapidly. The key representative enterprises with scale and R&D strength are Bochuang Technology, Fuchuang Optoelectronics, Guangxun Technology, Rihai Communication, Wuxi Love. Worth, Fuchunjiang Optoelectronics, Chengdu Feiyang, Datang Communications (Kunshan), Zhongshan Aokang AgileCom, Shanghai Shangcheng, etc., and more optical device companies and some fiber optic cable companies have been on and on the PLC optical splitter Package project. Because the packaging technology of the optical splitter is relatively simple and the investment is not large (about 200,000 yuan for a manual alignment system), the project is easy to complete. At present, there are many high value-added PLC device products, and the packaging technology has special process technology and proprietary technology. Domestic packaging manufacturers also need to increase R&D and investment in this aspect.
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