Huawei together with China Telecom launched the world's largest SDN commercial backbone network construction

According to China Telecom official information display, Huawei won the bid in 2015, China Telecom IDC bearer Private Network Central Purchasing items, including IDC hosting special aggregation routers, access routers (including SDN controller), as well as route reflector device.

The project will cover the construction of six major national telecom base core data centers, as well as 15 core data center of the city, and over the entire network based on the 400G router platform, SDN introducing innovative new technologies and other related network, which will become the world's largest SDN commercial backbone network, to achieve China Telecom cloud base and IDC interconnection between the provinces, to fully protect the rapid deployment and operations of China Telecom IDC / cloud hosting service quality requirements.

By the end of 2014, China Telecom Internet transformation strategy proposed, will be many aspects of the Internet-based operators and service-based business foundation NE, public Internet applications, government and enterprise information technology applications, cloud and big data and enterprise IT operations and other Internet upgrading of focus, a new type of China Telecom to create a comprehensive, full implementation of "de-telecommunications" strategy. With the implementation of China Telecom Internet transformation of network infrastructure also needs to adapt to the Internet reconstructed to meet service bearer "active, fast, flexible, and open" and other needs, but based on the IDC SDN backbone bearer network construction has become China Telecom Future one to build a new data center-centric network architecture key starting point for China Telecom network transformation in terms of significance.

The project lasted for several months, a number of major manufacturers at home and abroad are actively involved, and ultimately Huawei 400G platform with a mature and stable core routers and extensive commercial experience accumulated SDN field, China Telecom preferred cooperation manufacturers, together with China Telecom jointly build SDN world's largest commercial operator backbone network projects. All along, Huawei is committed to telecom operators to build trade advantages, and actively participate in the global SDN program, continued optimization SDN architecture and solutions, and working in partnership with telecom operators, in a data center as the core network architecture change, to become the world Operators ideal ICT transformation partner.

ROADM market entered a rapid growth period

According to well-known market research firm IHS Infonetics latest report shows that in the optical transmission market, in addition to still maintain a rapid growth outside 100G, ROADM market has become another one star. 2015 second quarter, ROADM market income ratio in the entire WDM market revenue up 45%. The report predicts that, ROADM market in 2015 revenue will grow 12% in 2104, and 2019, the market's compound annual growth rate as high as 12%, which greatly exceeds the entire WDM market compound annual growth rate of 9%, to become the next four years, WDM segment of the market the fastest growing segment.

Figure: Infonetics report ROADM market entered a rapid growth period

As can be seen from the chart IHS Infonetics report, in fact, starting in 2011, ROADM market performance had already started to speed, there's little need to explain that, 100G technology is also starting in 2011 at a global scale commercial. It is a coincidence?

Let's take a look at the status quo of large cities in China, the road to development, and perhaps give us some enlightenment. In recent years, some large cities continue to build and expand roads, often encounter the problem of the transformation of urban interchange. Some design and construction of transportation hub earlier, in the rapid development of today's urban road traffic has become the bottleneck. Similarly, the development of optical networks is also facing a similar situation. With 2011 global begin large-scale commercial 100G coherent optical transmission technology, many operators have seen the super-high-speed optical transmission technology challenge existing optical network architecture, and embarked on a strategy to reshape the optical network architecture project. Therefore, it is not a coincidence, but the optical network development inevitable trend.

Technology and market jointly call new networking technology of optical network

With the rise of Internet penetration to various industries in various fields, as well as cloud computing, big data, networking and other technology applications, data traffic is continuing to grow rapidly. According to IHS Infonetics analytical report 100G module shipments increased from 2011 in 2000 to 2014 or so quickly over 120,000. 100G optical transmission system on a global scale is rapidly expanding. In recent years, the industry has set his sights on Super 100G technology. Alcatel-Lucent deployed the world's first commercial 400G optical transport network in 2013, its 200G wavelength-division-board programmable achieve volume shipments in 2014. According to market analysts predict that by around 2017, 400G will gradually begin large-scale commercial.

You can see from the above data, ultra-high-speed optical transmission technology is rapidly improving the transmission capacity of the fiber, which makes electrical cross-way network to OTN optical network node is facing great challenges. According to the development trend of optical networks, long-distance backbone and metro core network topology often will tend to grid, the dimensions of each node may reach 8-dimensional, or even more. In this case, if pure electric cross 100G OTN networking mode, which means that the capacity of each node will reach 8x8T = 64T. If you consider the way for future 400G OTN network, then the capacity will be close to 200T, which is currently on the market, the largest capacity OTN electrical cross-connect equipment is far unable to meet. Meanwhile, large-scale OTN electrical cross matrix bound to bring higher power requirements and cooling requirements, as well as the difficulty of network evolution challenges operators have realized in the actual deployment of the deployment faced.

Future-oriented development, technology and markets are calling the new Optical Networking technology.

Huawei SDN program with a mature commercial experience

RR+ quasi-real-time traffic tuning programs respond to the complicated flow

SDN achieve the separation of control and forwarding, unified network management, on-demand deployment, and flexible scheduling. The arrival of the era of big data to make flood of data continue to impact the existing network equipment, flow variability, bandwidth imbalance is a common problem in the existing network. Huawei RR+ program like Dujiangyan flood of data traffic tuning, near real-time to deal with complex traffic. RR+ program without changing the current network structure of the premise, the use of the IGP collect reporting network topology and, through the visual interface is presented to the customer; uTraffic collect raw traffic statistics, and then polymerized into polymeric flow suitable particle size; NetMatrix traffic analysis Mining and achieve User-defined management stream will flow adjustment policies or constraints notice SNC; SNC-based tuning information issued under NetMatrix calculate the flow path, and the flow path through the distributed repeater adjust the BGP protocol, and ultimately dynamic traffic Adjustment.

Value-added services on-demand deployment, provide new revenue streams for operators

By SDN controller business chain solutions, enables centralized control and management of value-added services, each tenant demand every business use. The value-added business resource pooling, you can customize each service for each tenant various value-added services, such as for tenants A business can be a custom FW (Firewall) business for tenants A business 2 custom LB (LoadBalance) business, but also that business tenants B 1 while custom FW and LB business. When tenants need to add or change business needs, simply re-use SDN service stream draining to the different business process network element can not only improve resource utilization NE business, while achieving a rapid and flexible deployment of business, More operators to develop differentiated value-added services to provide a strong support and new revenue sources. In addition, Huawei SDN technology provides an open API interface, enabling network resources and business collaboration through a unified service control platform; also achieved a satisfying link utilization threshold and specific traffic QOS premise, intelligent selection lowest settlement lines, investment savings for users.

VxLAN technology to achieve a large two-story exchange, resource sharing

Cloud data centers must meet the needs of the virtual machine migration, in VLAN network, the virtual machine can only be Layer 2 network migration, and in order to be able to support virtual machine migration, needs to be pre-configured VLAN on the Layer 2 network, resulting in VLAN Configuring abuse, affecting quarantine VLAN broadcast domain, reducing the efficiency of the network. VxLAN (Virtuale Xtensible Local Area Network) This standard is in this context came into being, it has become one of the mainstream technology industry. VxLAN is a large two-story virtual network expansion tunnel encapsulation technology, the main technical principle is to introduce the outer tunnel a UDP format, as the data link layer, and the original packet payload contents as a tunnel to transfer . Since the outer layer of the UDP as a transport means, just to meet the IP payload data can make up easily in two three-network transmission, to achieve DC large two-story exchange, resource sharing, virtual machine migration and service remote DC clusters. In addition, existing only 4094 VLAN virtual network identity, can not meet the current network of large-scale data center needs, VxLAN provide 16M tenants ID, to fully meet the needs of data center logical isolation large-scale users and businesses.

Core exit router using industry-leading 400G cluster router NE5000E

Huawei cluster router NE5000E core to meet the IDC export bulk forwarding and high reliability requirements. NE5000E cluster router chip technology leadership, the use of independent innovation Sloar3.0 chip, forwarding capacity per slot reach 400Gbps, can support 80,000 families while online watch high-definition video, and smooth expansion to 400G 2 + 8 cluster, the cluster capacity exceeding 100Tbps future smooth evolution to 1T platform can meet the demands of IDC long-term business development.

Huawei apply industry-leading 400G technology with mature commercial experience SDN programs and mainstream industry VxLAN new technology, help Guangxi Mobile to build infrastructure agility, the ability to open and operational intelligence, control centralized IDC network, and provide a richer Guangxi mobile business models and revenue sources. Huawei has been in continuous innovation capabilities continue to explore the development of the road network, to provide users with an open, efficient, intelligent and flexible network IDC, the real future of cloud collar, Zhaopin world.

400G commercial need ultra low loss optical and opto-electronic hybrid cross

August 31 to September 2, the 17th China International Optoelectronic Exposition was held in Shenzhen, in the "2015 optical communication networks and technology innovation and development" thematic clubs held on September 1, the China Mobile Research Institute Network Technology Research Institute deputy director Li Han published "400G technology development and application of" special reports operators.

The development of business-driven trunk bandwidth rapid growth, 2012-2014 CMNET traffic increased by more than 100 percent per year, is expected to increase by the end of 2017 but also 7-15 times; backbone transmission network traffic by 30% -50% annual growth rate in recent It could double in a year. Specifically, as of 2014, China Mobile provincial backbone bandwidth of more than 80T, 2015 years will add 200T, China Mobile is currently building the world's largest 100G transmission network, and started to introduce ASON function. 100G show its superiority in the opening time, cost, power consumption, etc., more CMNET lay the foundation for development.

Opto-electric hybrid cross will become the future direction

Currently 100G OTN electrical cross-networking into the mainstream, opto-electric hybrid crossover also become the future direction of development, the introduction of photovoltaic hybrid cross, enabling businesses in a light layer of transparent transmission, to reduce cost and power consumption. But opto-electric hybrid cross to get the application must resolve performance testing, automated planning and layer synergy between other issues, which is critical in OTN applications SDN.

DC became the focal point for future traffic, the traditional network architecture challenges. Lee Han said China Mobile will be in DC for the core network construction, should face DC design, enhance DC traffic to divert to something. In addition, the 100G Internet era, the policy transport network protection needs to re-examine the introduction of ASON protection and restoration.

Ultra-low loss optical fiber demand urgent

Currently there are dual-carrier 400G and four-carrier scheme in which dual-carrier PM-16QAM modulation scheme is the industry's mainstream. Lee Han frankly, compared to 100G long-distance transmission system (about 3000km) need 5-6dB OSNR margin, currently 400G in the current network transmission margin is about 600km 2-4dB, still can not meet the long-distance trunk transmission needs. 400G PM-16QAM based on the current level of technology and current network conditions, such as to achieve 1000km transmission, you need a lot of aspects of the room, fiber, amplifiers, equipment upgrade for change.

At present, in the optical fiber field, Ultra-low loss and large effective area + Ultra-low loss represents the future direction of the optical fiber. Lee Han pointed out that the cost of cable construction giant, once laying is difficult to change, are strategic investments, fiber optic conduit at least need to consider the needs of the next 20 years, which means that today the deployment of optical fiber is bound to have the ability to ultra-low loss.

But the chain is weak, less commercial products, consider the deployment of a small amount of ultra-low-loss optical fiber network, to verify the performance of the existing network, and promote the development of the industry chain.

PMC metro OTN help China achieve 400G and OTN switching technology

Recently, PMC has released its newest DIGI-G4-- latest generation of OTN chip. PMC Chinese R & D Center for Communication Products Division Director Zhang Tianyu introduced to, DIGI-G4 is the first industry's highest density single-chip, can support 400G. Further integration of a large number of equipment manufacturers put the device on the board, resulting in a large power cost increases, while DIGI-G4 to peripheral devices incorporate internal, so that each port 100G power by 50%.

Interview, PMC DIGI-G4 product line manager Kevin representation, PMC developed this chip is completely respond to the needs of the market, that the rapid growth of bandwidth, the bandwidth will double every two years, which in the world are Such a trend. On the other hand, 100G become the standard has become a trend, this standard mainly in the backbone network, including China Mobile, China Telecom is largely concentrated in such a network backbone, certainly in terms of the operators to the metro, these bandwidth from the metro to the demand increase network access, metro bottleneck is additionally backbone.

In addition to bandwidth requirements, is the data center needs. Kevin stressed that large scale data centers, they are to complete the interconnection between the data centers. DIGI-G4 chip design at the beginning of this just like Google, AMAZON have conducted technical exchanges, they are particularly urgent need is encrypted. Light layer of encryption is not enough, mainly because we have to have encryption in the business layer, we DIGI-G4 chip encryption can be done in the 100G OTN, not only in 100G encryption, I can rate the operational level in my son's entire 100G You can be encrypted.

Zhang Tianyu said, OTN switching is actually OTN electrical cross concept think back 45 years ago when the mainstream use in backbone OTN, or one of the technical support line, in fact, a few years ago that is electrically OTN Cross into the mainstream over the past few years, we can see that a carrier is a strategy they deploy the branch line from the previous one turned into OTN switching, China at the forefront, China's leading OTN deployment in the world, We see in the world is a very clear trend in the world's top ten operators have nine full deployment of OTN electrical cross-based network, see the full flexibility of this technology to operators on services.

Currently, the chip supplier in terms of providing light to the equipment manufacturers a chip is not enough, cost pressures down the pressure from the operator level, for equipment operators in terms of R & D investment is controlled, previously invested heavily in software research and development team We do such a transmission device is unrealistic, so a lot depends on chip manufacturers, can have a complete package in the release of the chip at the same time available to them so that they can be completed within a short period of their development.

Zhang Tianyu finally said, PMC continues to invest in software, accounting for the company's software engineers than hardware engineers now, we offer a very complete package, and after the actual deployment verification, to reduce secondary research equipment manufacturers.

Technology of 400G optical modules

With the IEEE 100 Gbit/s (hereinafter referred to 100G) Ethernet standard-setting discussions with the end of the world's major manufacturers are promoting the global deployment of 100G and 400G focused its attention to even 1 Tbit/s system up. With 40G / 100G, like, 400G deployment should be a gradual manner. In order to make more effective use of existing DWDM (dense wavelength division multiplexing) line resources, reduce investment costs, operators can expect 400G deployment on existing networks, rather than re-design and build a new network to accommodate 400G of transmission. This means that you must adapt to the network design and planning 400G 100G / 40G or 10G to achieve a mixed deployment of 400G, 100G / 40G's.

1. Technical analysis 400G LAN Interface optical modules

400G LAN (Local Area Network) interface to optical modules may 100G Ethernet will continue to use proprietary parallel transmission. In February 2011, Finisar on "Beyond 100GE" seminar presented 400GE modules standard recommendation, primarily to support 400GE-LR16 and 400GE-SR16 two applications. Where 400GE-LR16 using 16×25G LAN WDM (1330,1310,1290 and 1270nm 4 waves channels) to achieve, and 400GE ~ SR16 is using a 16×25G multimode fiber interfaces. In addition, in the physical layer defines the CAUI (Attachment Unit Interface) -16, CPPI (parallel physical interface) -16 electrical interface standard. 16×25G 100GE just linear expansion, as long as the process to meet the requirements, there is no other technical difficulties. In contrast, the optical fiber parallel development will have more space, but supports higher densities needed photonic integration technology can make 400G commercially possible.

In addition, Finisar also proposed other possible ways 400G LAN applications: the first type is the use of already commercialization 4OG of EML (electro-absorption modulated laser) technology architecture composed of 10×40G; the second was that rely on technology to improve the EML, using 4-level amplitude modulation and DSP (digital signal processing) of dispersion compensation framework 8×50 G; third is 4×100G of architecture that must be complex amplitude phase modulation, such as PM-QPSK ( polarization multiplexing - Quadrature Phase Shift Keying), there is no possible commercialization of the technology demonstration.

NTT research report also pointed out that in the serial data transmission, 16×25G, 10×40G and 8X 50G of these types of architecture are possible. For 50G, modulation is also based MZ (Mach - Zehnder) the DQPSK (differential quadrature phase shift keying) modulation or OOK (on-off keying) modulation. Each architecture in size, cost, power consumption, etc. have their own advantages and disadvantages. From the current research point of view, DML (directly modulated laser) production process is simple, low power consumption, but the ER (extinction ratio) is small. EML complex production process, power consumption is relatively large, but the larger ER, you can get a very clear eye. Further, the quantum well EAM (electroabsorption modulator) InGaA1As based valence band offset is reduced due to a hole caused by accumulation in the modulation process, and therefore suitable for use as high-speed modulation. Figs. 1 to 3 are NTT in OFC 2011 show for the 400 GE of 1300nm, 50G EML spectrum, into the relationship between the current and the optical power and the transmission 10 and 40 km after the output eye diagram.

For 400GE systems, 50G of OOK modulation due to the physical size of the entire transmitter end, is a good compromise choice. In this modulation, DML comparison more difficult to implement. So we can predict, EML and 8×50G of OOK modulation prospects in 400GE systems.

2. Technical analysis 400G long-distance transmission optical modules

In the ITU-T / IEEE Joint seminars, Alcatel-Iucent report stated: interface cable OTU5 rate will reach 449.219 Gbit/s. With the increase rate, the system OSNR (optical signal to noise ratio), CD (chromatic dispersion), PMD (polarization mode dispersion) and nonlinear increasingly demanding. 400G signal dispersion tolerance of only 0.5 ps/nm, the 100G is 1 / 16.400G on OSNR also encountered a challenge, 6dB higher than the 100G. In particular, the use of higher than the current 7% FEC (forward error correction) after expenses, can achieve longer distances. The current discussion was more of a 25%. 400G 100G in PMD than the challenge faced bigger, 400G PMD tolerance of only 0.25ps, the 100G 1/4.

2.1 laser linewidth requirements

With the development of digital coherent receiver technology, the high-end multi-level modulation format because of its high spectral efficiency characteristics in DWDM systems are increasingly compelling. Phase noise characteristics of the laser transmitter and receiver optical local oscillator determines the bit error rate performance of the system. Table 1 lists the different modulation formats, 400G and 100G comparison with the laser line width requirements. Table, △fTX represents transmitter laser linewidth, △fLO represents wide receiver local oscillator light.

2.2 modulation formats and channel spacing feature

To meet the 400G DWDM transmission system in the current requirements and improves overall system capacity modulation pattern of the most important requirements are: to meet the SE (spectral efficiency) and OSNR sensitivity requirements, and have a very strong non-linear tolerance.

Theoretical capacity of single-mode fiber is 8 bit/s/Hz, the actual long-distance transmission equipment and optical fiber, a maximum of 4 bit/s/Hz. In modern optical communication systems, modulation format a great impact on system performance, in order to achieve with the existing network of 10G, 40G hybrid deployment, to achieve 80 wave 50 GHz spacing, it must meet high SE, which can be single-carrier high ary modulation or multi-carrier transmission is achieved. For 448G transmission system, consider the device frequency drift and R0ADM (reconfigurable OADM) non-ideal characteristics, requires practice must be 45G of 32QAM (quadrature amplitude modulation) modulation or 28G of PM ( polarization multiplexing) -256QAM. Electrical domain OFDM (Orthogonal Frequency Division Multiplexing) modulation of a single carrier can be substituted, as the complexity of both the DSP's, but due to the extra information OFDM cyclic prefix, preamble and training overhead symbols, etc., usually higher than the corresponding single-carrier format The SE is lower.

In order to try to meet a 50GHz DWDM channel spacing, many theoretical studies in 2010 are based on multi-level amplitude modulation, which PM-256QAM, a total of 65,536 constellation points, compared to 100G PM-QPSK, the density increases 8 times, and noise and light XPM (cross-phase modulation) / SPM (self-phase modulation) is very sensitive to transmission distance is very short. From the current situation reported demonstration of single-carrier QAM speed opinion, short term 448G transmission, whether it is a single carrier OFDM PM ~ 256QAM or electricity of 32QAM, it is not yet commercialized.

The first one kind of relaxed solution required SE: abandon 50GHz spacing WDM mandatory requirements, such as a 16QAM using 56G PM and flexibility of 70 ~ 80 GHz spacing WDM, SE of 6 ~ 5 bit/s/Hz, and the need There are more than enough to support ROADM systems. Data center users tend to use this flexible solution, but with large-scale, multi-service mesh network carriers to stick with standard spacing to 50GHz. For compatibility with a 50GHz boundary conditions, the use of inverse multiplexing can channel into two 448G 224G wavelength. 28G PM-I6QAM modulation up to 4 bit/s/Hz net SE, compared to 100G PM-QPSK, doubling the capacity of each fiber is increased in WDM. In addition, in order to achieve 10G, 40G / 100G to 400G seamless upgrade deployment of WSS (wavelength selective switch) presents an adjustable bandwidth requirements.

The first two kinds of solutions: using higher order modulation 32QAM or low photon carrier orthogonal multiplexing to replace the single-carrier 448G signal. This method is called coherent WDM or coherent optical OFDM. It is with inverse multiplexing DWDM different nature, because it can be obtained at a specific single carrier modulation format and the same SE coherent reception OSNR tolerance. A 448G of the transmitter can be used 10 separate photons modulated quadrature carriers. The receiver can be divided into two groups (each five as a group) to detect the reception. From the above discussion it seems, in order to obtain the highest possible rate of subcarriers can be processed on the electric field parallel to maintain a minimum light the large ones would be a more practical and more economical solution. Table 2 lists the OFDM and single carrier 400G system performance comparison.

Due to high sensitivity compared to a single carrier and excellent CD / PMD tolerance, multi-polarization digital coherent receiving CO (g coherent light) -OFDM becoming more promising and began to receive widespread attention in the industry. In the future exploration of 400G optical modules based on OFDM modulation structure, the main three kinds of architecture: Based on the FFT (Fast Fourier Transform) OOFDM (optical orthogonal frequency division multiplexing), all-optical OFDM and electro-optical OFDM.

Traditional OOFDM based DSP / DAC of IFFT (Inverse Fast Fourier Transform) and FFT signal synthesizing demodulation, CD and PMD tolerance can be inserted by a cyclic prefix or a guard interval, promoted training symbols, but this will resulting in a 10% or 20% of the overhead, and increase line speed. Especially in need of period CD compensation transmission line, the transmission performance DSP-based multi-carrier OFDM will be limited fiber nonlinear characteristics. The use of silicon-based PLC (Planar Lightwave Circuit) and hybrid integration technology LN (lithium niobate) lightwave circuit, the two carriers have been able to make the QPSK (quadrature phase shift keying) modulator to achieve single polarization modulator 100G (25G) and dual polarization modulator 111G (13.9G). Taking into account the complexity of the transmitter, unlike conventional DSP-based OFDM, the number of sub-carriers must less (usually 2 to 4), because of less number of subcarriers can effectively reduce PAPR. In addition, the transmitter does not require DSP and DAC. The use of a small amount of carrier, loop overhead will lead to additional costs or limit the ability to compensate. Because we need a receiver using a linear filter based on CD / PMD compensation.

All-optical OFDM, must be inserted GI (guard interval) to improve, CD and PMD tolerance, and requires a long symbol periods (many sub-carriers) to offset the cost of GI caused by electro-optical OFDM therefore proposed architecture to solve issue, electro-optical OFDM architecture to meet the higher speed requirements. Table 3 presents a comparison of the performance of 400G systems in a variety of different modulation formats.

In summary, the use of fewer sub-carriers, all-optical OFDM has the following two advantages: no emission end of DSP / DAC, has a relatively low electrical, optical complexity; As a result of fewer subcarriers , thereby reducing the PAPR of the signal, there are in the CD or the low dispersion compensating optical fiber line, having good nonlinear suppression. Therefore, from the cost, performance and complexity, etc. to achieve the look, all-optical OFDM modulation technique (2SC-DP-16QAM format) and channel spacing flexible optical module vendors can attract attention, it will play an important in the early commercial 400G role.

3. 400G detection technology

3.1 micro-optics and hybrid integration technology

For coherent detection, the use of separate free space 90° balanced mixer and a light detector to build coherent receiver system, this complex configuration to achieve commercialization is difficult. From the 2009 ECOC, U2T and HHI demonstrates monolithic integrated PLC 90°. Mixers and two pairs of high-speed balance PD receiver, to the 2010 ECOC, U2T and HH1 once again demonstrated monolithic two-way PLC 90°. Mixer and eight high-speed balancing PD receivers. From the evolution and development trend in recent years, it seems 100G transmission technology, 400G line receiver technology is gradually moving towards integration.

The integrated use of monolithic integrated receiver and free space optics, there is no way to get satisfactory performance, reliability and low cost. In this regard, NTT PLC technology using a silicon PBS (polarizing beam splitter) and 90°as a monolithic integrated optical mixer DPOH (polarized light mixer). Another use of a new multi-channel collimator DPOH the coupling loss between the lower and the PD, and to suppress coupling deviation caused by temperature changes. In addition, NTT has developed a high-speed chip-level compact photoelectric conversion structure, and use these techniques to produce an integrated coherent receiver. Micro-optical alignment technology allows greatly improved sensitivity based PD matching and temperature performance PLC hybrid integrated devices.

Since the silicon-based microelectronics plane technology, optoelectronic devices is three-dimensional technology. Compared to hybrid integration, PIC (Photonic Integrated Circuit) can significantly reduce the size of the optical module, save packaging costs and flat connection allows the optical path to match and balance easier, thus effectively control deviation, it is the future mainstream. Currently Bell Labs has been research on monolithic silicon integrated coherent detection technology, but there are many technical difficulties to be a breakthrough. 400G early in the silicon PLC and free space optics hybrid integration will be more mature commercial programs.

3.2 with detection technology

Digital coherent reception technology in the field of high-speed transmission is generally regarded as a promising technology because it can increase the sensitivity of the system OSNR, CD and PMD compensation line transmission damage. Because electricity rates "bottleneck", ADC sampling rate will be limited to a very long period of time of less than 100 GS/s. In order to effectively address this issue in 400G even T bit/s channel transmission, the use of multi-carrier modulation format is an effective method.

The use of wavelength-independent detection, the receiver hardware complexity can bring lower by detecting a plurality of sub-carriers, not only from ADC sampling rate bottleneck constraints, and reduce the load on DSP. The structure shown in the block diagram of an optical transceiver module 4.

3.3 processing capabilities within power

Currently in 100G systems, most of the optical device has reached the extent of commercial, but in coherent receiver technology, the key to the biggest problem ADC and DSP chip production business is the processing power and power consumption. Although in 2010, Alcatel-Lucent has 112 G's long-distance system uses a 70M + door of 56 GS/s of ADC / DSP, but faces the same prediction in the 400G system bottleneck.

4. Conclusion

400G long-distance communication and transmission of the light entering a new era, the multi-carrier multi-level phase modulation and an array of optical communications is moving from single-carrier modulation with coherent detection of the polarization multiplexed coherent change detection. Photonic integration and electronic integration, ADC / DSP technology will be 400G optical communication modules and systems business of the key. With the urgent need for standardization of Ethernet, parallel light of the requirements of photonic integration technology will be a huge boost. In the next 2 to 3 years, 400G electro-optical OFDM-related technologies will gradually mature, although these devices have a certain distance from the commercial cost and power consumption, but as these technologies have matured and related standards of discussion and development, 400G commercial system is about to pull the curtain.