CN1564487A - Passive optical network using carrier intercepting multi-address access/conflict detection protocol - Google Patents
Passive optical network using carrier intercepting multi-address access/conflict detection protocol Download PDFInfo
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- CN1564487A CN1564487A CNA2004100177027A CN200410017702A CN1564487A CN 1564487 A CN1564487 A CN 1564487A CN A2004100177027 A CNA2004100177027 A CN A2004100177027A CN 200410017702 A CN200410017702 A CN 200410017702A CN 1564487 A CN1564487 A CN 1564487A
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Abstract
In the invention, 1XN fiber coupler of passive optical tapping element in traditional passive optical network access system is replaced by NXN fiber coupler. Optical signal loop back configuration is carried out for ports at terminal of optical route of optical fiber coupler by using (N-2)/2 pieces of optical fiber jumpers. Thus, signal transmission route between optical network elements is changed to 'optical network element- fiber coupler- optical network element' from 'optical network element- terminal of optical route- optical network element' so as to reduce time delay of signal transmission. Therefore, CSMA/CD protocol can be utilized in up going multiple address access control in passive optical network access system. The invention is suitable to broadband optical access system.
Description
Technical field
The present invention relates to the EPON in the optical access network system, be specially the ring of light that makes carrier sense multiple access/collision detection (CSMA/CD) agreement can be used for the access control of EPON connecting system uplink multi-address and return configuration, belong to fiber optic communication field.
Background technology
In the optical access network, EPON can economical and effective and transmitting high speed data and be used as the preferred option of optical access network pellucidly.EPON is by with the optical line terminal of backbone network or metropolitan area network interfaces, form with the optical network unit of local network of users interfaces and middle passive light distribution network.Wherein, the passive light distribution network is by a feeder line optical fiber, and a 1 * N fiber coupler and the N root distribution optical fiber as passive optical splitter is formed.Feeder line optical fiber connects optical line terminal and fiber coupler, and N root distribution optical fiber connects fiber coupler and N optical network unit.
Ethernet since with low cost, technology maturation reliable, be easy to advantage such as networking, in local area network (LAN), obtained popularizing in a large number.2000 the end of the year first mile Ethernet alliance EPON connecting system based on Ethernet is proposed, and facilitate IEEE to begin to formulate corresponding standard the range of application of Ethernet is extended to Access Network from local area network (LAN) in December, 2000.1 * N fiber coupler has been isolated the upward signal of each optical network unit in the EPON, if do not take certain measure, each optical network unit must be transmitted by optical line terminal just can receive the signal that other optical network unit sends.Because the coverage of Access Network is greater than the coverage of local area network (LAN), optical network unit is to the signal transmission delay that distance caused of the optical line terminal delay requirement greater than CSMA/CD agreement operate as normal.So in the standard that IEEE formulates, only adopted time division multiple access to insert this a kind of uplink multiple access modes, and abandoned the CSMA/CD agreement that existing Ethernet uses fully based on the EPON of Ethernet.
Owing to do not continue to use the CSMA/CD agreement, IEEE has to increase functions such as Multi-point Control Protocol and point-to-point emulation to adapt to the physical topology of EPON point-to-multipoint on the layer functions of existing Ethernet, has caused based on the architecture of the EPON of Ethernet and existing Ethernet compatibility fully.
Summary of the invention
The objective of the invention is to make EPON can continue to continue to use the CSMA/CD agreement as its uplink multi-address access control protocol, thereby needn't increase functions such as Multi-point Control Protocol and point-to-point emulation, the compatibility of maintenance and existing ethernet architecture helps quick, low cost development based on the passive optical network equipment of Ethernet.
For realizing such purpose, the present invention changes the 1 * N fiber coupler that is used as passive optical splitter in the traditional passive optical network access system into N * N fiber coupler, and fiber coupler is carried out the light signal loop-back configuration at the port of optical line terminal side with (N-2)/2 optical patchcord, a part of uplink optical signal is looped back to each optical network unit place, make the signal propagation path between optical network unit and the optical network unit become " optical network unit → fiber coupler → optical network unit " by " optical network unit → optical line terminal → optical network unit ", reducing the signal transmission delay between optical network unit and the optical network unit, thereby make carrier sense multiple access/collision detection (CSMA/CD) agreement can continue on for the uplink multi-address access control of EPON connecting system.
The concrete light signal loop-back configuration of the present invention is as follows: N port of the optical network unit side of N * N fiber coupler still links to each other with N optical network unit by N root distribution optical fiber; A port of the optical line terminal side of fiber coupler links to each other with optical line terminal by feeder line optical fiber, and a port is terminated, and remaining N-2 port links to each other in twos by (N-2)/2 optical patchcord.Like this, directly set up the physical channel by fiber coupler between each optical network unit, reduced the signal transmission delay between optical network unit and the optical network unit greatly.
Can use CSMA/CD will no longer be subjected to the influence of feeder line fiber lengths as the uplink multi-address access control protocol of EPON this moment, and only be subjected to the influence of power budget and distribution fiber lengths etc.
The luminous power that is about uplink optical signal power 1/N is by the up optical line terminal of passing to; Be about uplink optical signal power (N-2)/N
2Luminous power given each optical network unit by loopback.Can satisfy the optical power budget requirement under the general applicable cases.
The maximum length of distribution optical fiber can be expressed as:
Maximum length=maximum round trip time delay/(4 * unit propagation delay), (1)
Wherein " unit propagation delay " is the unit propagation delay of light in optical fiber, and " maximum round trip time delay " is the maximum round trip time delay of signal between two optical network units.The maximum round trip time delay depends on " time slot (slotTime) " and " filling bit (jamSize) " these two parameters of stipulating in IEEE's 802.3 standards:
Maximum round trip time delay=(time slot-filling bit)/bit rate.(2)
By the regulation of IEEE's ethernet standard 802.3, jamSize is 32 bits, and slotTime is respectively 512 and 4096 bits when bit rate is 100Mbit/s and 1000Mbit/s.Typically getting the unit propagation delay of light in optical fiber is 5 μ s/km, is calculated as can be known by (1) and (2) formula that maximum length is about 240m when upstream rate is 100Mbit/s; Maximum length is about 200m when upstream rate is 1000Mbit/s.It should be noted that when upstream rate should work in the carrier extend pattern during for 1000Mbit/s, after than the short frame of slotTime, add a carrier extend territory artificially, make frame length equal 4096 bits.In addition, can use the frame burst mechanism to prevent the loss in efficiency that when transmitting a large amount of short frame, causes and the obvious decline of performance because of carrier extend.
Principle of the present invention and configuration are all very simple, are easy to realize.Make based on the EPON connecting system of Ethernet and can continue to use CSMA/CD as its uplink multi-address access control protocol, keep the compatibility with existing ethernet architecture, this will help utilizing ripe ethernet technology carry out based on the EPON connecting system equipment of Ethernet fast, low cost development.
Description of drawings
Figure 1 shows that the present invention uses the system block diagram of CSMA/CD as the EPON of uplink multi-address access control protocol.
Embodiment
Figure 1 shows that and proposed by the invention can use the system block diagram of CSMA/CD as the EPON of uplink multi-address access control protocol.Fiber coupler among the figure is N * N fiber coupler.N * N fiber coupler still links to each other with N optical network unit by N root distribution optical fiber at N port of optical network unit one side.In optical line terminal one side of fiber coupler, a port of fiber coupler is connected to feeder line optical fiber, and links to each other with optical line terminal by feeder line optical fiber, and a port is terminated, and remaining port interconnects by optical patchcord in twos.Through such light signal loop-back configuration, the wavelength that each optical network unit sends is λ
uUplink optical signal at the fiber coupler place except some is uploaded to optical line terminal, some can be passed to each optical network unit under loopback each port by the optical network unit side of fiber coupler along optical patchcord.Like this, the optical network unit in the system is λ except the wavelength that the reception optical line terminal sends
dDownlink optical signal outside, can also receive that the wavelength that other optical network unit sends is λ
uUplink optical signal, thereby can realize the uplink multi-address access control by the CSMA/CD agreement.
Because it is identical that the length of optical patchcord can be configured to, the delay inequality of the light signal of process different fiber wire jumper loopback will only depend on the difference of fiber coupler inner couplings light path light path.And the difference of general fiber coupler inner couplings light path light path is very little, and experiment shows that its influence to the loopback optical signal quality can ignore.
Claims (1)
1, a kind of EPON that uses carrier sense multiple access/collision detection protocol, its feature adopts N * N fiber coupler and fiber coupler is carried out the light signal loop-back configuration at the port of optical line terminal side, fiber coupler links to each other with N optical network unit by N root distribution optical fiber at N port of optical network unit side, optical line terminal one side at fiber coupler, a port of fiber coupler links to each other with optical line terminal by feeder line optical fiber, a port is terminated, remaining port interconnects by optical patchcord in twos, such light signal loop-back configuration make uplink optical signal that each optical network unit sends at the fiber coupler place except some is uploaded to optical line terminal, some is passed to each optical network unit along optical patchcord under loopback each port by the optical network unit side of fiber coupler, optical network unit is except the downlink optical signal that the reception optical line terminal sends, can also receive the uplink optical signal that other optical network unit sends, thereby can insert/access of collision detection protocol realization uplink multi-address by carrier sense multiple.
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| CNA2004100177027A CN1564487A (en) | 2004-04-15 | 2004-04-15 | Passive optical network using carrier intercepting multi-address access/conflict detection protocol |
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| CNA2004100177027A CN1564487A (en) | 2004-04-15 | 2004-04-15 | Passive optical network using carrier intercepting multi-address access/conflict detection protocol |
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN100426741C (en) * | 2005-07-22 | 2008-10-15 | 中兴通讯股份有限公司 | Automatic configurating method for EPON net element device |
| CN101277152B (en) * | 2007-03-27 | 2012-09-05 | 闫晓峰 | Annular double-bus redundancy protection architecture of passive optical network |
-
2004
- 2004-04-15 CN CNA2004100177027A patent/CN1564487A/en active Pending
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN100426741C (en) * | 2005-07-22 | 2008-10-15 | 中兴通讯股份有限公司 | Automatic configurating method for EPON net element device |
| CN101277152B (en) * | 2007-03-27 | 2012-09-05 | 闫晓峰 | Annular double-bus redundancy protection architecture of passive optical network |
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