外文翻譯---寬帶光纖接入網(wǎng)的發(fā)展趨勢(shì)

1、<p>　　Wide band optical fiber access network trend of development</p><p>　　Author: Liu Jinhai article source: Computer universal time: 2005-3-8</p><p>　　This article first is brief introduc

2、ed the world broadband access network develops the condition and the main application, next narrated the wide band optical fiber access network merit. With emphasis has once more analyzed the wide band point-to-point act

3、ive Ethernet optical fiber system and the wide band to the passive optical fiber system characteristic and the application. Meets down proposed our country optical fiber access network sends chem. possible to surmount AP

4、ON, BPON and the EPON st</p><p>　　The broadband access network develops condition and main application</p><p>　　In fact, looking from the telecommunication development history, when the network

5、number of users achieves certain scale. Each kind of application meets the nature production; this also is so-called steps the Cuff law might to be at especially. In the history one kind of technology since birth has not

6、 been having a big pile of application, regardless of is the mobile communication or the Internet, on its short note, the browsing, the net chats and so on the key applications all is develops certa</p><p>　

7、　Since has entered for the 21st century, the whole world broadband access network entered the big development phase. To 2004 year's end, the total number of users already achieved 150,000,000, became in the electrici

8、ty reliable historical account to develop one of quickest telecommunication services, and even was also quicker than the mobile service. For example the whole world mobile service from 10,000,000 developed to 100,000,000

9、 has spent for 5.5 years, but the broadband access service has on</p><p>　　The Asian and Pacific area, specially South Korea's and Japan were the broadband access develop the swiftest most and violent co

10、untry, the South Korean wide band user total already break through 10,000,000, the wide band popular rate occupied the world first, hold family 7 Internet 90%. Japanese Government also vigorously advances the wide band d

11、evelopment through each measure, plans in 2005 to enhance the wide band user total to 30,000,000, in which FTTH achieves 1 10,000.US still is the world </p><p>　　Speaking of the optical fiber access network,

12、 specially the optical fiber to station (FTTP) or optical fiber proficient (FTTH), the whole world already started to enter the unloading phase, only US had 270 FTTP projects, was mostly the local authority, the public c

13、ompany, the property developer and the non-leading telecommunication operation business project. Leading operation business also starts to enter this domain, in which Version plans in 2005 to complete 3,000,000 FTTP; SBC

14、 in the plan pl</p><p>　　Our country broadband access network extremely is also rapid in the near two year development, according to the preliminary statistics, to 2004 year's end our country wide band u

15、ser is 25,000,000, becomes is inferior to US's second big broadband access market, in which leadership technology is only ADSL, probably accounts for about 70%, next is the Ethernet technology, but also has few wide

16、band wireless turning on and electric cable modem turning on, also occupies regarding the FTTH technology </p><p>　　Looking from the wide band application that, according to the American Mai Kenxi Company

17、9;s newest analysis, the initial period wide band application mainly is the high speed surfer, may make the surfer the time to increase approximately 30%.Hereafter, along with the service large-scale development, develop

18、s the power which the new service becomes continues to develop. According to American BHK Corporation demonstrated in 2004 investigation result that, in 2003 the American first five wide band e</p><p>　　Need

19、s to point out that, discusses needs to pay attention to in a basic understanding using the actuation the erroneous zone, namely cannot place hopes in artificially studies beforehand develops 12 items so-called “the Assa

20、ssin's mace application”, promoted application. In fact, looking from the telecommunication development history, when the network number of users achieved certain scale, each kind of application meets the nature prod

21、uction; this also is so-called steps the Cuff law might to b</p><p>　　Wide band optical fiber access network superiority</p><p>　　Along with the optical fiber in the toll network, the metropolit

22、an area network and even the access network branch section massive applications, the logical trend of development will be continues to the access network to match the line segment and to direct the inlet part to extend,

23、the key is advances the speed quickly? This will be decided by many kinds of factors, including the market demand, the competition need, the application stimulation, the technical progress, the cost drop and necessar<

24、/p><p>　　Below mainly will analyze several kind of main wide band optical fiber turning on technology from the system technology angle the characteristic, the question and the trend of development. Certainly, b

25、esides the system technology, affects its application the factor to be very many, mainly is the service and the application as well as the control policy. In addition, each kind of necessary primary device technology and

26、 the placing installment test technology extremely is also essential. At presen</p><p>　　The point-to-point active Ethernet </p><p>　　Because system the cost, the quality, the management, the se

27、curity and so on many kinds of factors, the Ethernet still had further to improve as the public network turning on way.</p><p>　　The traditional Ethernet belongs to the user in network (cPN).However its appl

28、ication actually in to include the access network other public network domain expansion. In the history, regarding business user application environment, the Ethernet technology always is the most popular method, at pres

29、ent has become only definitely in the power supply receptacle second big housing and the office public facility connection. Uses the Ethernet is had the huge network foundation and the long-term experie</p><p&

30、gt;　　Regarding the public network housing user application environment, the point-to-point active Ethernet system uses the active service focus point to substitute the passive point-multipoint system the passive componen

31、t, enables the transmitting range to be possible to expand to 1 20 kilometer far. The main merit is special-purpose turning on, the band width has the guarantee, each user may monopolize 100Mb/s and even 1dbs; Bureau end

32、 equipment simple cheap; The transmitting range is long, the serv</p><p>　　Because the cost, the quality, the management, the security and so on many kinds of factors, the Ethernet still had further to impro

33、ve as the public network turning on way. Mainly is the Ethernet technology inherent mechanism does not provide the end-to-end package time delay, the package loss rate, the band width control, supports the real-time serv

34、ice with difficulty the grade of service, lacks the safety mechanism guarantee and so on.</p><p>　　Point-multipoint passive, light network system</p><p>　　Along with IP rising with the developme

35、nt, some people proposed the EPON concept, this thought obtained the positive response in the Ethernet, has already formed the GEPON standard in under the IEEE 802.3ah flag.</p><p>　　1. Passive light network

36、ing</p><p>　　Passive light network (PoN) is one pure medium network, its main characteristic has removed the active equipment in the access network, thus has avoided the electromagnetic interference and the

37、thunder and lightning influence, reduced line and the external instrumentation failure rate, reduced correspondingly has transported the Augur cost. Next, the PON service transparency is good, the band width is wide, sui

38、tably in any service pattern and the speed signal, can support the simulation broadcas</p><p>　　The PON main shortcoming is the disposable investment cost is high, because bureau end light line terminal OLT

39、is very expensive, the optical fiber and the shunt and so on the passive infrastructure must an arriving, when like this the number of users are few or the user distribution surpasses some definition is away from, each u

40、ser's cost is very high. Moreover, its tree branch topology caused the user not to have the protection function or the protection function cost is high, has affected the</p><p>　　2. APON AND BPON</p&g

41、t;<p>　　The early narrow band passive light network is based on TDM, the performance price compared not well, already naturally withers away. An ATM passive light network (APON/BPON) may use ATM the centralism and

42、 the statistics multiplying, the recombination passive shunt to the optical fiber and the light line terminal sharing function, enable the performance price compared to have the important improvement, at present in count

43、ries and so on US and Japan already started commercial.</p><p>　　However, the actual APON/BPON service adaptive provides at present very complex, provision of service ability is limited, the data transmissio

44、n rate and the efficiency are not high, the cost is high, but its market prospect as a result of ATM decline dim. Finally, looking from the long-term service trend of development that, the APON available band width was s

45、till insufficient. Take FTTC as the example, although the typical branch downward speed may reach 622Mb/s, after but because the by-pass, </p><p>　　3. EPON/GEPON</p><p>　　Along with IP rising wi

46、th the development, some people proposed the EPON concept, namely in with APON and the BPON similar structure and in the O.983 foundation, tries to retain its essence part - physics level PON; But replaces ATM by the Eth

47、ernet to take the link level agreement, constitutes one to be possible to provide a greater band width, the </p><p>　　Low cost and wider professional ability new marriage - EPON. This thought obtained the po

48、sitive response in the Ethernet; in IEEE802.Under the 3ah flag has already formed the GEPON standard. In reality, EPON and the GEPON basic difference is the standardization, the former often </p><p>　　Refers

49、 to the non-sign equipment, the latter refers conforms to IEEE 802.3ah, standard equipment. Moreover, the GEPON transmitting range and the by-pass compare have compared to EPON reduce.</p><p>　　EPON/GEPON an

50、d the traditional point-to-point Ethernet main different place lies in the work in the point-multipoint mailing address. Its downward direction work in the TDM way, the data stream changes the long </p><p>　

51、　Ether frame way to broadcast ONU, each ONU basis ether frame MAC address, decision choices. The upward direction work in the TDMA way, Comes from the different time slot ONU data stream to gather the public optical fibe

52、r facility and OLT. In addition, the traditional Ethernet work in the continual optical transmission pattern, is receiving and dispatching two directions both is the continual bit class, therefore receives the end fixed

53、time easily to realize with the decision. But the EPON/GEPOkI</p><p>　　Looked from the EPON/GEPON structure that, its essential merit </p><p>　　Enormously simplified the traditional multi-layere

54、d overlapping network </p><p>　　Structure, the main characteristic included:</p><p>　　- - Eliminated ATM and the SDH level, thus reduced the initial cost and the movement cost; </p><p

55、>　　- - The downward service speed reaches as high as 1Gb/s, the permission support multi-user, each user's band width may be higher, and can provide video frequency professional ability and good QOS</p><

56、;p>　　- - The hardware is simple, does not need outdoor electronic installation, and enables the installment deployment work to simplify;</p><p>　　- - May use the Ethernet technology mature chip massively,

57、 the realization is simple, the cost low</p><p>　　- - improved the electric circuit to refer to the coordination service nimbly provision with the reshuffle ability.</p><p>　　IEEE 802.3ah the st

58、andard GEPON technology standards is good, on the downward wave length is 1310 and 1490nm, on the downward speed is 1.25Gb/s, the transmitting range is 10/20km, the by-pass compared to is 16, the primary service is the d

59、ata and the sound of talking, </p><p>　　after increases a 1550nm visual broadcast wave length, becomes the sound of talking, the data and the television method of three-in-one “triple-play” the wide band ser

60、vice colligation service, but this will be the future family service “the Assassin's mace application”.</p><p>　　The EPON/GEPON main shortcoming is the efficiency low and supports outside the Ethernet wi

61、th difficulty the service. The former is because uses 8B/10B the line code, introduces 20% band width loss, in addition other expenses, available load only about 50%, but APON and GPON </p><p>　　all use NRZ

62、to harass the code are the line codes, does not have the band width loss.</p><p>　　In addition reasons and so on load bearing plate efficiency, transmission gathering plate efficiency, service adaptive effic

63、iency, cause the EPON/GEPON total transmission efficiency to be very low, probably only is GPON half.</p><p><b>　　4. GPON</b></p><p>　　In 2001, formulated EPON standard positively wh

64、ile IEEE, the FSAN organization starts to initiate the formulation speed to surpass 1Gb/s PON network standard 1,000,000,000,000,000 Ethernet passive light network (GPON), afterwards, ITU-T also involved this new standar

65、d formulation work and 1 Dan (speed enhances in 2003 through two related GPON new standard G.984.1 and G.984.2 to 2.5Gb/s). According to this newest standard stipulation, GPON may provide 1.244 and the 2.488Gb/s downward

66、 speed and th</p><p>　　Seals the existing SDH network each kind of data signal the general standard signal adaptive mapping technology, may adapt any subscriber signal form and any transmission network servi

67、ce pattern, namely may according to the inherent form transmission pronunciation, the data and the video signal, does not need to attach ATM or the P seal level, has manifested the service provider comprehensively to the

68、 provision of service nimble request, but APON/BPON and EPON/GEPON all need to provide the speci</p><p>　　From the technical angle, GPON is the BPON inheritance and the development, GPON has inherited BPON v

69、ery many essential features, for example both all use the same OLT nucleus, the heart technology, and uses the similar physical optical fiber facility and the luminous power budget and so on. On the other hand, GPON has

70、used some newest technology achievement, besides most important GFP seal, but also includes the forward-acting error correction and so on the new technology.</p><p>　　From the service which provides looked,

71、not only GPON may provide 10/100Mb/s,1Gb/s the service, moreover may provide the VLAN service and the pronunciation service, in fact might adapt any view to have the service and the future new service adaptive request. T

72、otal looking at, GPON is not the manufacturer actuation technical standard, but is one kind of operation business actuation standard, therefore has the thoroughbred operation benefit to consider, the speed is higher, may

73、 reach 2.4Gb/s; Has </p><p>　　Because three kind of PON capital expenditures (70% all are approximately) the light connections, thus its hardware cost should differ not much, but because in the realization t

74、echnology difference, the GEPON difficulty is at present smallest, the cost is lowest. But speaking of the transmission efficiency, then GPON regardless of is harassing the code efficiency, the transmission gathering pla

75、te efficiency, the load bearing agreement efficiency and the service adaptive efficiency aspect all is </p><p>　　GPON and EPON/GEPON face the together challenge includes: How can have nine load bearing TDM s

76、ervice on Ethemet/GFP and can provide the telecommunication level the grade of service; Next, because GPON and EPON/GEPON are select to the multi-spot star type or the shape of tree network, will need 1+1 and passes thro

77、ugh the different route light network through one to realize the telecommunication level protection to restore the request, the network cost extremely is high; Third, at present GPON and</p><p>　　Recently so

78、me people to optical fiber communications development scene, somewhat puzzled. First, in 2000 the IT profession froth, caused the optical fiber communications the scale of production investment oversized, the overproduct

79、ion, in the IT profession many small companies went out of business. Specially the optical fiber, overseas dumps to China. Second, some people thought that, Optical fiber communications through-put capacity already achie

80、ved 10Tbps, could not use up nearly, moreover the</p><p>　　The author will believe that, optical fiber communications technology still have the very big development space, will be able to have the very big d

81、emand and the market from now on. Mainly is: The optical fiber to family FTTH, the light exchange and the integrated photoelectron component aspect can have the big development. Mainly discusses the optical fiber communi

82、cations in this the trend of development and the market..</p><p>　　Generally speaking, the optical fiber access network has represented the broadband access network long-term development direction, each kind

83、 of wide band optical fiber access network all has its best use situation and the opportunity, the wide band point-to-point active Ethernet optical fiber system suits in the low density user dispersible area application,

84、 the wide band point-multipoint passive optical fiber system most suits newly built or the reconstruction crowded user area should. Our coun</p><p>　　寬帶光纖接入網(wǎng)的發(fā)展趨勢(shì)</p><p>　　作者：劉金海 文章出處：計(jì)算機(jī)世界 時(shí)間：

85、2005-3-8</p><p>　　本文首先簡(jiǎn)要介紹世界寬帶接入網(wǎng)發(fā)展的狀況和主要應(yīng)用；其次講述了寬帶光纖接入網(wǎng)的優(yōu)點(diǎn)；再次重點(diǎn)分析了寬帶點(diǎn)到點(diǎn)有源以太網(wǎng)光纖系統(tǒng)和寬帶點(diǎn)到多無(wú)源光纖系統(tǒng)的特點(diǎn)和應(yīng)用。接下來(lái)提出我國(guó)光纖接入網(wǎng)的發(fā)展可能跨越</p><p>　　APON、BPON和EPON階段，從寬帶點(diǎn)到點(diǎn)以太網(wǎng)光纖系統(tǒng)和GEPON開(kāi)始，乃至最終過(guò)渡到GPON階段的初步設(shè)想。最后從各個(gè)角度

86、剖析了光纖通信技術(shù)的發(fā)展趨勢(shì)。</p><p>　　寬帶接入網(wǎng)發(fā)展的狀況和主要應(yīng)用</p><p>　　事實(shí)上,從電信發(fā)展歷史看，當(dāng)網(wǎng)絡(luò)用戶數(shù)達(dá)到一定規(guī)模。各種應(yīng)用會(huì)自然產(chǎn)生，這也是所謂的邁特卡夫定律的威力所在。歷史上沒(méi)有一種技術(shù)生來(lái)就帶著一大堆應(yīng)用的，無(wú)論是移動(dòng)通信還是互聯(lián)網(wǎng)，其短信、瀏覽、網(wǎng)上聊天等關(guān)鍵應(yīng)用都是在用戶規(guī)模發(fā)展到一定程度后自然產(chǎn)生的，而不是事先刻意設(shè)計(jì)策劃出來(lái)的。<

87、/p><p>　　進(jìn)入21世紀(jì)以來(lái)，全球?qū)拵Ы尤刖W(wǎng)進(jìn)入了大發(fā)展階段。到2004年底,總用戶數(shù)已經(jīng)達(dá)到1.5億，成為電信史上發(fā)展最快的電信業(yè)務(wù)之一，甚至比移動(dòng)業(yè)務(wù)還快。例如全球移動(dòng)業(yè)務(wù)從1000萬(wàn)發(fā)展到1億花了5.5年，而寬帶接入業(yè)務(wù)僅用了3.5年。按照IDC的預(yù)測(cè)，2007年全球?qū)拵Э傆脩艨梢赃_(dá)到2.09億，其中9.9，即大約2000萬(wàn)用戶為光纖接入網(wǎng)。 </p><p>　　亞太地區(qū)，特別是

88、韓國(guó)和日本是寬帶接入發(fā)展最迅猛的國(guó)家，韓國(guó)寬帶用戶總數(shù)已經(jīng)突破1000萬(wàn)，寬帶普及率居世界第一，占據(jù)家庭的7互聯(lián)網(wǎng)的90%。日本政府也通過(guò)各種措施大力推進(jìn)寬帶發(fā)展，計(jì)劃2005年將寬帶用戶總數(shù)提高到3000萬(wàn)，其中FTTH達(dá)到1000萬(wàn)。美國(guó)依然是世界最大的寬帶接入市場(chǎng)，總用戶數(shù)超過(guò)3000萬(wàn)。美國(guó)FOC將寬帶業(yè)務(wù)定位為2003—2008年的六大目標(biāo)之一，事實(shí)上寬帶接入正成為美國(guó)普遍服務(wù)的下一個(gè)目標(biāo)。美國(guó)寬帶接入是以電纜電視和ADSL為

89、主發(fā)展的，由于電信管制政策鼓勵(lì)采用新技術(shù)建設(shè)網(wǎng)絡(luò)(例如FCC規(guī)定運(yùn)營(yíng)商建設(shè)光纖接入網(wǎng)可以不受限于本地環(huán)路的非捆綁政策)以及競(jìng)爭(zhēng)和業(yè)務(wù)增長(zhǎng)的壓力，近來(lái)主導(dǎo)運(yùn)營(yíng)商對(duì)光纖到駐地(FTTP)的發(fā)展十分積極。</p><p>　　就光纖接入網(wǎng)，特別是光纖到駐地(FTTP)或光纖到家(FTTH)而言，全球已經(jīng)開(kāi)始進(jìn)入啟動(dòng)階段，僅美國(guó)就有270個(gè)FTTP項(xiàng)目，多半是地方政府、公共公司、房地產(chǎn)開(kāi)發(fā)商和非主導(dǎo)電信運(yùn)營(yíng)商的項(xiàng)目。主導(dǎo)

90、運(yùn)營(yíng)商也開(kāi)始進(jìn)入該領(lǐng)域，其中Version計(jì)劃2005年完成300萬(wàn)FTTP，SBC在其龐大的“光速”計(jì)劃中計(jì)劃2007年達(dá)1800萬(wàn)FTTN，每戶具備速率20-39Mb/s，提供端到端的三重業(yè)務(wù)捆綁(trite play)業(yè)務(wù)。日本是世界上推進(jìn)FTTH最激進(jìn)的國(guó)家，2004年其光纖就已經(jīng)通達(dá)1800萬(wàn)多戶家庭，但是用戶發(fā)展滯后，大約為200萬(wàn)，2005年計(jì)劃發(fā)展1000萬(wàn)。歐洲比較穩(wěn)健保守，到2004年FTTH總共敷設(shè)了50萬(wàn)，有16

91、7個(gè)小項(xiàng)目或試驗(yàn)項(xiàng)目在進(jìn)行。</p><p>　　我國(guó)寬帶接入網(wǎng)在近兩年發(fā)展也十分迅速，據(jù)初步統(tǒng)計(jì)，到2004年底我國(guó)寬帶用戶為2500萬(wàn)，成為僅次于美國(guó)的第二大寬帶接入市場(chǎng)，其中主導(dǎo)技術(shù)是ADSL，大約占70%左右，其次是以太網(wǎng)技術(shù)，還有少量寬帶無(wú)線接入和電纜調(diào)制解調(diào)器接入，對(duì)于FTTH技術(shù)還處在跟蹤階段，少數(shù)發(fā)達(dá)城市也已經(jīng)在開(kāi)始考慮和試驗(yàn)各種FTTHI技術(shù)。</p><p>　　從寬帶

92、應(yīng)用看，按照美國(guó)麥肯錫公司的最新分析，初期的寬帶應(yīng)用主要是高速上網(wǎng)，可以使上網(wǎng)的時(shí)間增加約30%。此后，隨著業(yè)務(wù)的大規(guī)模拓展，開(kāi)發(fā)新的業(yè)務(wù)成為繼續(xù)發(fā)展的動(dòng)力。據(jù)美國(guó)BHK公司在2004年的調(diào)查結(jié)果顯示，</p><p>　　2003年美國(guó)前五名的寬帶消費(fèi)是網(wǎng)上賭博、成人節(jié)目、游戲、音樂(lè)下載和點(diǎn)播電視，具有明顯的向消費(fèi)類傾斜的趨勢(shì)。</p><p>　　需要指出，討論應(yīng)用驅(qū)動(dòng)需要注意一個(gè)基本

93、認(rèn)識(shí)上的誤區(qū)，即不能寄希望于人為事先研究開(kāi)發(fā)出一二項(xiàng)所謂“殺手锏應(yīng)用”、推廣應(yīng)用。事實(shí)上，從電信發(fā)展歷史看，當(dāng)網(wǎng)絡(luò)用戶數(shù)達(dá)到一定規(guī)模，各種應(yīng)用會(huì)自然產(chǎn)生，這也是所謂的邁特卡夫定律的威力所在。歷史上沒(méi)有一種技術(shù)生來(lái)就帶著一大堆應(yīng)用的，無(wú)論是移動(dòng)通信還是互聯(lián)網(wǎng)，其短信、瀏覽、網(wǎng)上聊天等關(guān)鍵應(yīng)用都是在用戶規(guī)模發(fā)展到一定程度后自然產(chǎn)生的，而不是事先刻意設(shè)計(jì)策劃出來(lái)的。</p><p>　　寬帶光纖接入網(wǎng)的優(yōu)勢(shì)</p

94、><p>　　隨著光纖在長(zhǎng)途網(wǎng)、城域網(wǎng)乃至接入網(wǎng)主干段的大量應(yīng)用，邏輯的發(fā)展趨勢(shì)將是繼續(xù)向接入網(wǎng)的配線段和引入線部分延伸，關(guān)鍵是推進(jìn)速度有多快，這將取決于多種因素，包括市場(chǎng)的需求、競(jìng)爭(zhēng)的需要、應(yīng)用的刺激、技術(shù)的進(jìn)步、成本的下降和配套運(yùn)行系統(tǒng)的開(kāi)發(fā)等等。我國(guó)2008年舉辦奧運(yùn)會(huì)和2010年舉辦世界博覽會(huì)這兩大事件將會(huì)在一定程度上推進(jìn)寬帶光纖接入網(wǎng)的發(fā)展。</p><p>　　下面將主要從系統(tǒng)技術(shù)

95、的角度來(lái)分析幾種主要的寬帶光纖接入技術(shù)的特征、問(wèn)題和發(fā)展趨勢(shì)。當(dāng)然，除了系統(tǒng)技術(shù)外，影響其應(yīng)用的因素很多，主要是業(yè)務(wù)和應(yīng)用以及管制政策。此外，各種配套元器件技術(shù)和敷設(shè)安裝測(cè)試技術(shù)也十分關(guān)鍵。目前低成本光源已有望實(shí)現(xiàn)，850nm的VCSEL僅需幾美元,1310nm的VOSEL已有突破，速率達(dá)10Gb/s。PLC混合集成技術(shù)高密度低成本光纜及相關(guān)技術(shù)，對(duì)彎曲不敏感的室內(nèi)用光纖，低成本無(wú)源器件，施工安裝技術(shù)，自動(dòng)光操作測(cè)試系統(tǒng)等也都是影響光接

96、入網(wǎng)推廣應(yīng)用的關(guān)鍵因素，需要有妥善的解決方案。 點(diǎn)到點(diǎn)有源以太網(wǎng)系統(tǒng) </p><p>　　由于計(jì)費(fèi)、質(zhì)量、管理、安全等多種因素，以太網(wǎng)作為公用網(wǎng)接入方式尚需進(jìn)一步改進(jìn)。</p><p>　　傳統(tǒng)以太網(wǎng)屬于用戶駐地網(wǎng)(cPN)。然而其應(yīng)用卻在向包括接入網(wǎng)在內(nèi)的其他公用網(wǎng)領(lǐng)域擴(kuò)展。歷史上，對(duì)于企事業(yè)用戶應(yīng)用環(huán)境，以太網(wǎng)技術(shù)一直是最流行的方法，目前已成為取決于供電插口的第二大住宅和辦公室

97、公用設(shè)施接口。采用以太網(wǎng)作為企事業(yè)用戶接入手段的主要原因是已有巨大的網(wǎng)絡(luò)基礎(chǔ)和長(zhǎng)期的經(jīng)驗(yàn)知識(shí)。目前所有流行的操作系統(tǒng)和應(yīng)用也都是與以太網(wǎng)兼容的、性能價(jià)格比好、可擴(kuò)展性、容易安裝與開(kāi)通以及高可靠性等。</p><p>　　對(duì)于公用網(wǎng)住宅用戶應(yīng)用環(huán)境，點(diǎn)到點(diǎn)有源以太網(wǎng)系統(tǒng)采用有源業(yè)務(wù)集中點(diǎn)來(lái)替代無(wú)源點(diǎn)到點(diǎn)系統(tǒng)的無(wú)源器件，使傳輸距離可以擴(kuò)展到120公里之遠(yuǎn)。主要優(yōu)點(diǎn)是專用接入帶寬有保證；每個(gè)用戶可以獨(dú)享100Mb/s乃

98、至1dbs；局端設(shè)備簡(jiǎn)單便宜；傳輸距離長(zhǎng)，服務(wù)區(qū)域大；成本隨用戶數(shù)的實(shí)際增長(zhǎng)而線性增加，無(wú)需規(guī)劃，投資風(fēng)險(xiǎn)低，因而在低密度用戶分散地區(qū)成本較低。缺點(diǎn)是兩端設(shè)備和光纖設(shè)施專用，用戶不能共享局域端設(shè)備和光纖，當(dāng)需求快速增長(zhǎng)且用戶很密集時(shí)，光纖和兩端設(shè)備數(shù)量及其成本以及空間需求也隨之迅速增加，因而不太適合高密集用戶區(qū)域。影響選擇以太網(wǎng)技術(shù)的另一個(gè)因素是傳統(tǒng)視頻業(yè)務(wù)的提供方式，例如美國(guó)地方貝爾公司都承諾提供傳統(tǒng)模擬RF視頻節(jié)目，而以太網(wǎng)和模擬視