Abstract: the main development hotspots in the field of optical fiber communication technology are briefly described and prospected, including ultra-high speed transmission system,

Ultra-large capacity wavelength division multiplexing system, optical network technology, new generation optical fiber, IP over SDH and IP over.

Optical and optical access network.

Keywords: ultra-high speed optical fiber transmission ultra-large capacity wavelength division multiplexing optical network

The birth and development of optical fiber communication is an important revolution in the history of telecommunications.

With the reform of telecom management system and the gradual and comprehensive opening of telecom market, the development of optical fiber communication appears again.

This paper aims to make a brief description and prospect of the main development hotspots in the field of optical fiber communication.

1 development of ultra-high speed system

Judging from the development history of telecommunications in the past twenty years, the demand for network capacity and the improvement of transmission rate have always been a pair of experts.

Contradictions The development of traditional optical fiber communication has always been carried out in the form of electrical time division multiplexing, whenever the transmission rate

If it is increased by four times, the cost per bit will be reduced by about 30% ~ 40%. Therefore, the economic benefits of high bit rate system are roughly as follows

Exponential growth, which is why the transmission rate of optical fiber communication system has lasted for more than 20 years.

The root cause of growth. At present, the commercial system has been upgraded from 45Mbps to 10 Gbps, and the speed has increased in 20 years.

20O0 times, which is much faster than the integration speed of microelectronic technology in the same period. The appearance of high-speed system not only increases the industry.

The service transmission capability also makes it possible to realize various new services, especially broadband services and multimedia services.

At present, the 10Gbps system has started to equip networks in large quantities, and more than 5,000 terminals and repeaters have been installed all over the world.

It has been widely used in North America, Europe, Japan and Australia. China will also start field trials in the near future.

It should be noted that the 10Gbps system is sensitive to the polarization mode dispersion of optical cables, while the laid optical cables are not.

It must meet the requirements for opening and using the 10Gbps system, and can only be installed and opened after actual testing and verification.

Theoretically, the speed of the above high-speed system based on time division multiplexing is expected to be further improved, for example, in the laboratory.

The transmission rate reaches 4OGbps, and dispersion and polarization mode dispersion compensation and pseudo-ternary (that is, double binary) are adopted.

It can be transmitted after encoding 100km. The method of using time division multiplexing of electricity to improve transmission capacity is close to that of silicon and gallium.

Due to the limitation of arsenic process, there is not much potential to be tapped. In addition, the 40Gbps system is cost-effective and practical.

Whether it can be successful is still unknown, so the more realistic way out is to turn to recycling, which has many benefits.

There are many kinds, but at present, only wavelength division multiplexing (WDM) mode has entered the large-scale commercial stage, and other modes are still being tested.

Research stage.

2 Evolution to Ultra-large Capacity WDM System Optical Fiber Access | Optical Fiber Transmission

As mentioned above, the expansion potential of the time division multiplexing system using electricity has been exhausted, but the available bandwidth of the optical fiber is 200nm.

Less than 1% of the source has been utilized, and 99% of the resources have yet to be explored. If a plurality of light sources with appropriately staggered wavelengths are transmitted,

The transmission of signals on a polar optical fiber at the same time can greatly increase the information transmission capacity of optical fiber, which is wavelength division multiplexing (WDM).

The main advantage of using WDM system is that (1) can make full use of the huge bandwidth of optical fiber.

Source, so that the capacity can be rapidly expanded several times to hundreds of times; (2) A large number of optical fibers can be saved during large-capacity and long-distance transmission.

The transmission cost is greatly reduced; (3) It has nothing to do with signal rate and electric modulation mode, but it introduces wide bandwidth.

Convenient means to bring new business; (4) Using WDM network to realize network exchange and recovery is expected to be transparent and reliable in the future.

High survivability optical network.

In view of the great benefits of the above applications, major technological breakthroughs and market drive in recent years, wavelength division multiplexing (WDM) system.

The development of China Unicom is very rapid. If 1995 is taken as the take-off year, its global sales are only 1 100 million dollars, while in 2000,

It is estimated that it will exceed USD 4 billion in 2005 and reach USD 654.38+0.2 billion in 2005. The development trend is surprising.

There are more than 3,000 WDM systems in the world, and the maximum capacity of practical systems reaches 320 Gbps (2 *16 *10 Gbps).

Lucent has announced that it will launch an 80-wavelength WDM system with a total capacity of 200Gbps(80*2.5Gbps).

Or 400Gbps(40* 10Gbps). The highest level in the laboratory reached 2.6Tbps( 13*20Gbps). This is unpredictable.

After a long period of practical application, the capacity of the system can reach the level of 1Tbps, which can be considered as a super-large capacity dense wavelength division multiplexing system in recent two years.

The development of optical fiber communication system is another milestone in the development history of optical fiber communication, which not only thoroughly develops endless optical transmission links.

Capacity has also become the catalyst for the explosive development of IP services and the foundation of flexible optical nodes in the next generation optical transport network.

3 Realizing Optical Network-Strategic Direction

Although the above practical wavelength division multiplexing system technology has huge transmission capacity, it is basically point-to-point communication.

The flexibility and reliability of letter-based systems are not ideal. If the optical path can be similar to SDH in the power supply.

The add-drop function and cross-connect function on the road undoubtedly add a new layer of power. According to this basic idea,

Optical add-drop multiplexer (OADM) and optical cross-connect device (OXC) have been successfully developed in the laboratory. The former has always been

Put into commercial use.

The basic purposes of optical networking are: (1) to realize ultra-large capacity optical networks; (2) to achieve network scalability, allowing

The number of nodes and traffic of the network are increasing; (3) Realize the reconfiguration of the network and achieve the purpose of flexible reconfiguration of the network.

Purpose; (4) Realize the transparency of the network and allow the interconnection of signals of any system and different standards; (5) to achieve fast

Network recovery, the recovery time can reach100 ms.

In view of the above potential advantages of optical networks, developed countries have invested a lot of manpower, material resources and financial resources.

Pre-research, especially a series of optical network projects funded by DARPA, such as Be 1 1core.

Mainly developed the "Optical Network Technology Cooperation Plan (ONTC)" and the "All Optical Communication Network" mainly developed by Lucent.

Research Plan, Multi-wavelength Optical Network (MONET) and National Transparent Optical Network (NTON), etc. In Europe and

In Japan, there are similar optical network projects. Optical fiber access | optical fiber transmission.

To sum up, optical networking has become another new climax of optical communication development after SDH electrical networking. Its standardization

This work will be basically completed in 2000, and the commercialization time of its equipment will be around 2000.

The bright, highly flexible and super-large-capacity national backbone optical network can not only provide the future national information infrastructure (

NII) has laid a solid material foundation and laid a foundation for China's information industry and national economy in the next century.

As well as national security, has extremely important strategic significance.

4 new generation optical fiber

In recent years, with the explosive growth of IP traffic, the telecommunication network has begun to develop towards the sustainable development of the next generation.

Exhibition, and the construction of optical fiber infrastructure with huge transmission capacity is the physical foundation of the next generation network. Traditional G.652

Single-mode fiber has been exposed that it can not meet the development needs of the above-mentioned ultra-high-speed long-distance transmission network.

Developing new optical fiber has become an important part of developing the next generation network infrastructure. At present, in order to adapt to trunk lines,

According to the different development requirements of network and metropolitan area network, two different new types of optical fibers, namely non-optical fibers, have emerged.

Zero dispersion fiber (G.655 fiber) and waterless absorption peak fiber (full wave fiber).

4. 1 The basic design idea of a new generation of non-zero dispersion fiber (G.655 fiber) is 1550.

The working wavelength region of the window has reasonable low dispersion, which is enough to support the long-distance transmission of 10Gbps without dispersion compensation.

Thus saving the cost of dispersion compensator and its additional optical amplifier; Meanwhile, its dispersion value remains non-zero,

It has a minimum value (such as above 2ps/(nm.km)), which is enough to suppress four-wave mixing and cross-phase modulation.

System and other nonlinear effects, suitable for opening DWDM system with sufficient wavelength, and meet the development of TDM and DWDM at the same time.

Direction. In order to achieve the above goal, the zero dispersion point can be moved to the short wavelength side (usually1510 ~1520 nm

Range) or long wavelength side (near 157nm), so that its working wavelength region near 1550nm presents a certain size of color.

The typical dispersion value of G.655 fiber in the wavelength range of 1550nm is that of G.652 fiber 1/6 ~.

1/7, so the dispersion compensation distance is about 6 ~ 7 times that of G.652 fiber, and the dispersion compensation cost (including optical amplifier,

Dispersion compensator and installation and debugging) are much lower than G.652 fiber.

4.2 Compared with long-distance networks, full-wave optical fiber metropolitan area networks are facing a more complex and changeable business environment, and should directly support large-scale networks.

Users, so they need frequent traffic grooming and bandwidth management capabilities. But its transmission distance is very short, usually only

50 ~ 80 km, so fiber amplifier is rarely used, and fiber dispersion is not a problem. Obviously, in such an application ring,

In this case, how to use optical fiber to transmit data most economically and effectively becomes a key factor in network design.

High-density wavelength division multiplexing technology with hundreds of multiplexed wavelengths will be a promising solution. At this time, you can

So as to distribute services to different wavelengths at different rates and route and add services on the optical path.

In this application, the development of optical fiber with as wide available bandwidth as possible becomes the key.

The main factor is the water absorption peak near 1385nm, so if we can try to eliminate this water peak, the available spectrum of the fiber will be reduced.

It is expected to expand greatly. Full-wave optical fiber was born in this situation.

Full-wave optical fiber adopts a brand-new production process, which can almost completely eliminate the attenuation caused by water peak.

Except that there is no water peak, full-wave fiber is the same as ordinary standard G.652 matched cladding fiber. However, because there is no water peak,

Water peak, optical fiber can open the fifth low-loss window, bringing a series of benefits:

(1) The available wavelength range is increased by 100nm, which increases the total available wavelength range of optical fiber from about 200nm to.

300nm, the number of reusable wavelengths is greatly increased;

(2) In the above wavelength range, the dispersion of optical fiber is only half of the wavelength range of 155nm, which is easy to realize.

Now high bit rate long-distance transmission;

(3) Different services can be allocated to the wavelength transmission that is most suitable for this service, thus improving network management;

(4) When the available wavelength range is greatly expanded, the allowable wavelength range is wider, and wavelength accuracy and stability are very important.

Looking for lower components such as light source, combiner and splitter, the cost of components, especially passive components, is greatly reduced.

Decrease, thus reducing the cost of the whole system.

5 IP over SDH and IP over Optical

Data service based on IP service is the main driving force of the development of information industry in the world at present, so can it be effective?

Supporting IP services has become a symbol of whether new technologies can have a long technical life.

At present, both ATM and SDH can support IP, which are called IP over ATM and IP over SDH respectively.

IP over ATM takes advantage of the advantages of fast speed, fine granularity and multi-service support of ATM, and the simplicity and flexibility of IP.

The characteristics of easy expansion and unification can achieve the goal of complementary advantages, but the disadvantage is that the network architecture is complex.

The transmission efficiency is low and the overhead loss is high (up to 25% ~ 30%), and the combination of SDH and IP can just make up for the above IP over.

The weakness of ATM. The basic idea is to map IP packets directly to SDH frames through Point-to-Point Protocol (PPP), which saves time.

Removed the complicated ATM layer in the middle. The specific method is to package IP packets into PPP packets first, and then frame them by HDLC.

Then the byte synchronization is mapped to the VC package of SDH, and finally the corresponding SDH overhead is put into STM-N frame.

IP over SDH essentially retains the connectionless characteristics of the Internet as an IP network and forms a unified plane network.

Simplify the network architecture, improve the transmission efficiency, reduce the cost, be easy to assemble IP and be compatible with different technologies.

The main advantage of this system is that it can save the header overhead and IP over which are indispensable for ATM mode.

ATM encapsulation and sectional assembly function increase the penetration rate by 25% ~ 30%, which is very expensive for WAN.

It is very precious. The disadvantage is that the network capacity and congestion control ability are poor, and the routing table of large-scale network is too complicated, which can only

Service classification does not give priority to service quality, which makes it difficult to ensure the quality of high-quality services and is not suitable for multi-service platforms.

With the commercialization of gigabit high-speed routers, its development momentum is growing.

Very strong. The key to adopting this technology is gigabit high-speed router, which has made a breakthrough recently, such as the United States.

The 12000 series Gigabit Switch Router (GSR) introduced by domestic Cisco Company can achieve Gigabit rate.

At present, Internet service routing has multi-bandwidth switching capability of 5 ~ 60 Gbps, providing flexible congestion management and grouping.

Broadcast and QOS functions, its backbone network rate can be as high as 2.5Gbps, and it can be upgraded to 10Gbps in the future.

The port density and port cost of router can be comparable to ATM, and the packet forwarding delay is reduced to tens of microseconds.

This is no longer a problem. In short, with the maturity of gigabit high-speed routers and the great development of IP services, IP over

SDH will be more and more widely used. Optical fiber access | optical fiber transmission

But in the long run, it is possible when the IP traffic increases gradually and the link capacity is higher than 2.4Gbps.

Eventually, the middle SDH layer will be omitted, and IP will run directly on the optical path, forming a very simple and unified IP network structure (IP over

Optical). Obviously, this is the simplest and most direct architecture, which saves the middle ATM layer and SDH layer and reduces the number of users.

Layering, reducing network equipment; Reduce function overlap, simplify equipment and reduce network management complexity.

Especially the complexity of network configuration; The extra overhead is the lowest and the transmission efficiency is the highest; Through traffic engineering design, you can

To match the asymmetric traffic characteristics of IP; You can also use the protective optical fiber of the optical fiber ring to absorb the sudden business and do what you can.

Avoid caching and reduce delay; Due to the cancellation of expensive ATM switches and a large number of ordinary SDH multiplexing equipment, it is simplified

Except for network management and wavelength division multiplexing technology, its total cost is expected to be one or two orders of magnitude lower than that of traditional circuit-switched networks!

To sum up, the real world is diverse, and network solutions will not be a single and specific technical choice.

The use is also related to the background of specific telecom operators. All three IP transmission technologies will be used in different periods of telecommunication network development.

Different parts of the network play their due historical roles. But from the perspective of the future, IP is better than optical fiber.

Will be the most long-term vitality technology, especially as IP business gradually becomes the leading business of the network, this kind of right

The most ideal transmission technology of IP services will become the dominant transmission technology of future networks, especially backbone networks.

In the new era, IP over ATM, IP overSDH and IP over Optical will complement each other and have their own advantages.

Use occasions and fields.

6 Means to solve the bottleneck of the whole network-optical access network

In the past few years, the core of the network has undergone earth-shaking changes, whether it is exchange or transmission.

It has been updated for several generations. Soon, this part of the network will become completely digital, dominated and controlled by software and high technology.

On the other hand, the existing access network is still dominated by twisted-pair copper wire (90%).

Above), primitive and backward simulation system. The huge technical contrast between the two shows that access network has really become a restrictive factor.

Bottleneck of further development of the whole network. At present, although there have been a series of technical means to solve this bottleneck problem, such as double

XDSL system on twisted pair, HFC system on coaxial cable, broadband wireless access system, but they can only be regarded as some.

Transitional solution, the only long-term technical means to completely solve this bottleneck problem is optical access network.

The main purposes of using optical access network in access network are: reducing maintenance and management costs and failure rate; Develop new equipment,

Increase new income; Cooperate with local network structure adjustment, reduce nodes and expand coverage; Make full use of optical fiber

A series of benefits; Building transparent optical network to meet the multimedia era. The so-called optical access network may

Includes optical digital loop carrier system (ODLC) and passive optical network (PON). Digital loop carrier system

DLC is not a new technology, but it combines the open interface VS. 1/V5.2 to transmit the integrated DLC(ID) on the optical fiber.

LC), showing great vitality. For example, in the United States, DLC/IDLC has occupied 654.38+300 million subscriber lines.

36 million lines, of which IDLC accounts for 27 million lines. In particular, 50% of new subscriber lines are IDLC, accounting for about 5 million lines every year.

As for passive optical network technology, it is mainly paid attention to in Germany and Japan. Germany scored around 230 before the end of 1996.

Ten-thousand-line optical access network system, in which PON accounts for about 6.5438+0 million lines, and Japan regards PON as the main technology of its network fibrosis.

Technology, unremitting research for more than ten years, adopted a series of technical and technological measures to reduce the copper cost of passive optical networks.

The cost of optical cable stranding is equivalent. The construction of optical access network has been fully started in 1998, and it will reach 6000 in 20 10.

Ten thousand lines, the basic popularization of optical fiber communication network, as a countermeasure to revitalize the economy 2 1 century. I plan to fight for it again recently.

By 2005, the optical fiber communication network will be realized. Optical fiber access | optical fiber transmission

In the development of passive optical network, a broadband passive optical network based on ATM has recently appeared.

(APON), this technology combines the advantages of ATM and PON, and the transmission rate can reach 622/ 155Mbps, which can

Providing an economical and efficient multimedia service transmission platform and making effective use of network resources represents the multimedia era.

Important strategic direction of access network development. At present, ITU has basically completed the standardization work, and it is expected that

Commercial equipment will come out at 1999. I believe that in the future passive optical network technology, APON will occupy a place.

The increasing share has become the main development direction of broadband investment technology facing 2 1 century.

7 concluding remarks

Judging from the development status and trends of the above aspects related to optical fiber communication, there is every reason to think that optical fiber communication.

Letters have entered another new climax of vigorous development. This time, the development climax covers a wider range and has more technical updates.

Difficult, the influence and influence are also wider, which is bound to have a far-reaching impact on the entire telecommunications network and information industry.

The result of evolution and development will largely determine the future pattern of telecommunication network and information industry, and will also be of great significance to the next century.

Social and economic development has a great impact.