ethernet in the first mile over point-to-point fiber … in the first mile over point-to-point fiber...

Ethernet in the First Mile Over Point-to-Point Fiber (EFMF)

FUJITSU NETWORK COMMUNICATIONS INC.2801 Telecom Parkway, Richardson, Texas 75082-3515Telephone: (972) 690-6000(800) 777-FAST (U.S.)us.fujitsu.com/telecom

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OverviewSince 1980, Ethernet has been the dominant enterprise LAN protocol. Several popular Ethernet standards, including 10Base-T, 100Base-T, and 1000Base-T for copper, and 1000Base-LX for fiber, have enabled deployment to grow to roughly half a billion ports worldwide.

In the last few years, Ethernet has solved the bandwidth bottleneck in aggregation networks and is the technology best suited to provide access to customers—the so-called last mile of broadband access. New standards are being developed by the EFM task force (IEEE 802.3ah) that position Ethernet as the single technology to deliver universal broadband access for high-end user applications, while enabling true end-to-end, seamless technology integration in communications.

The EFMF standards are aimed at the physical layer for point-to-point fiber with Ethernet at speeds of 100 Mbps and 1 Gbps, and spanning lengths of at least 10 km over single-mode fiber that will allow a broad range of applications. The following chart shows global Ethernet standards for all the main physical media in use today, as well as the new ones for copper and fiber to support EFM.

Minimum Reach

100 m 500 m 750 m 2000 m 2700 m 5000 m 10 km 20 km0

2 Mbps

10 Mbps

100 Mbps

1 Gbps

10 Gbps

Max

imu

m B

and

wid

th (S

ymet

ric)

100Base-L/BX10(Single Mode Fiber)

2Base-TS(SHDSL)

10Pass-TS-TS(VDSL) 10

00B

ase-

PX

20

10 GigE

1000Base-LX (SMF)

ExistingIEEE 802.3Standards

EFMCIeee 802.3ah

EFMFIEEE 802.3ah

1000Base-T(MMF)

100Base-T(Cu Cat 5)

100Base-FX(MMF)

10Base-T(Cu Cat 5)

1000BaseB/L/PX10

Figure 1: Global Ethernet Standards including EFMF and EFMC

Based on the existing IEEE 802.3 fiber optic standards, the EFMF adds support for both single and dual fiber, as well as support for an extended temperature range (from –40 to +85 degrees C), making it suitable for outside deployments that need to withstand a variety of environmental conditions.

As Figures 2 and 3 show, the 100 Mbps option will probably make more sense for residential or small office access. This option is likely to get early traction because of the lower cost (in terms of processor speed, memory and buffers) of building Fast Ethernet switches. This will allow an easier way into the market for cautious operators, whereas the Gigabit Ethernet options will be more appropriate for small and medium enterprises.

For your convenience, a list of acronyms can be found at the end of this document.


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CentralOfficeNode

1 or 2Fiber Strands

Maximum Distance 10 km

100Base-LX10 or100Base-LX10U

100Base-LX10 or100Base-LX10D

Figure 2: Small Home or Office

For small/medium enterprises and residential access in multi-tenant units, there will likely be an aggregation link between the access or aggregation node and the CO.

CentralOfficeNode

Aggregation Link

Maximum Distance 10 km

1000Base-LX10 or1000Base-LX10U

1000Base-LX10 or1000Base-LX10D

Cat 5, SMF or MMF100 or 1000 Mbps

Figure 3: SME or Residential Access, Point-to-Point Gigabit Ethernet Aggregation

Within the building, the network would reach the desktop or the individual subscriber in the multi-tenant unit with either Category 5 cable or copper.


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EFMF PMD SublayerThe following table shows where EFMF fits in terms of the existing Fast Ethernet and Gigabit Ethernet standards.

100 Mbps 1000 Mbps

SMF SMF

Dual Fiber 100Base-LX10, 10 km1000Base-LX, 5 km

1000Base-LX10, 10 km, Extended Temperature

Single Fiber100Base-BX10-D, 10 km 100BaseBX10-U, 10 km

1000Base-10BX-D, 10 km 1000Base-BX-U, 10 km

Table 1: Standards for EFMF

EFMF adds a new set of standards to the IEEE 802.3 standards suite by introducing support for single SMF. Most importantly, for a subscriber access technology, EFMF allows extended temperature and reach capabilities for both Fast Ethernet and Gigabit Ethernet.

EFMF supports symmetrical, high bandwidth and full duplex point-to-point links. Both the 100 Mbps option and the Gigabit Ethernet option are implemented through SMF by multiplexing the laser signal into different wavelengths. A 10 km span will be supported with standard SMF.

There are high-volume MAC chip-sets available for both the 100 Mbps and the 1 Gbps options, and early EFMF rollouts will take advantage of this. EFMF is created with a new PMD layer; and as Figure 3 shows, the PMD is implemented as the bottom sublayer on Layer 1.


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OSI Reference Model

Layers LAN CSMA/CD

Layers

Application

Presentation

Session

Transport

Network

Higher Layers

LLC - Logical Link Control

OAM (Optional)

Reconciliation

MII

PCS

PMA

PMD

PHY

Medium

MAC Control (Optional)

MAC Media Access Control

LAN CSMA/CD Layers

Higher Layers

LLC - Logical Link Control

OAM (Optional)

Reconciliation

MAC Control (Optional)


Data Link

Physical

PCS

PMA

PMD

Medium

100 Mbps Link Segment 1000 Mbps Link Segment

GMII

MDI MDI

PHY

Figure 4: The PMD as a Sublayer of the PHY

The dual fiber options transmit in the send and receive directions on separate fibers, and the single fiber options have a multiplexer to split the send and receive signals into two wavelengths and consolidate fiber usage accordingly.

Dual Fiber StandardsThe dual fiber options are 100Base-LX10 and 1000Base-LX10. These standards use separate fibers for transmitting the send and receive directions.

100Base-LX10The 100Base-LX10 support is for single-mode, dual fiber connections at a signaling speed of 125 Mbps. 100Base-LX10 has a reach of over 10 km. The optical output power of the laser (Pout) is –15 dBm with a sensitivity of –25 dBm. 100Base-LX10 uses 4B/5B NRZI encoding. The wavelength plan makes it possible to use existing OC-3/STM-1 optical TRx. The encoding scheme makes it possible to use existing 100Base-X chipsets.

1000Base-LX10The Gigabit Ethernet option (1000Base-LX10) supports a signaling speed of 1250 Mbps, operating on single mode, dual fiber at lengths of greater than 10 km. The optical power (Pout) is –9.5 dBm with a sensitivity of –20 dBm and a transmit wavelength of 1260–1360 nm.


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Gigabit EFMF can also be run on multimode dual fibers at a span of greater than 550 meters. The Pout for this option is –11 dBm with a sensitivity of –20 dBm and a transmit wavelength of 1310 nm. 8B/10B encoding is used to leverage existing Gigabit Ethernet standards. 1000Base-LX10 standardizes the vast amount of pre-standard Gigabit Ethernet TRx deployed today.

1000Base-LX10 TRx

2 Fiber Strands

1000Base-LX10 TRx

Figure 5: Dual Fiber Option for Gigabit EFMF

Single Fiber StandardsThe single fiber options, described in the following sections, depend on the use of a special multiplexer placed in front of the laser as illustrated in Figure 6. The signal is split into transmit and receive wavelengths.

Single G.652 Fiber

1.3 µm Receiver

1.5 µm Laser 1.3 µm Laser

1.5 µm Receiver

Figure 6: Two-Wavelength Device (the figure illustrates one possible solution of separating wavelengths)

The laser and receiver are in the same package where the optical light path is split into a second and third window by the WDM filter. This filter has a typical insertion loss less than one decibel.

100Base-BX10100Base-BX10 supports single-mode, single fiber and a signaling speed of 125 Mbps. It also supports greater than a 10 km span. The optical output is –14 dBm with a sensitivity of –29.2 dBm. The single fiber support is made possible because the uplink TRx and downlink TRx are transmitting on different wavelengths:

• Downlink at 1480 to 1580 nm• Uplink at 1260 to 1360 nm

The downlink PMD is called 100Base-BX10-D and would typically be located in the central office or similar POP presence, whereas the uplink 100Base-BX10-U PMD is located at subscriber premises. This new PMD for single fiber access is illustrated in Figure 7.


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100Base-BX10-D 100Base-BX10-U

1 Fiber StrandFigure 7: PMD for Single Fiber Access

Because the send and receive directions are on different wavelengths, only a single fiber is needed.

1000Base-BX10The 1000Base-BX10 specification provides single-mode, single fiber support at a signaling speed of 1250 Mbps for a span of greater than 10 km. The optical output is –9 dBm with a sensitivity of –20 dBm. The uplink 1000Base-BX10-U TRx and downlink 1000Base-BX10-D are transmitting on different wavelengths:

• Downlink at 1480 to 1500 nm• Uplink at 1260 to 1360 nm

Again, the downlink would be located in the central office or similar POP presence, whereas the uplink is located at subscriber premises. The PMD for single fiber Gigabit Ethernet is illustrated in Figure 8.

1000Base-BX10-D 1000Base-BX10-U

1 Fiber Strand

Figure 8: PMD for Single Fiber Gigabit EFMF Support

As with the Fast Ethernet option, only a single fiber is needed when you multiplex the transmit and receive directions into different wavelengths.


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Wavelength OverlaysThe following figure illustrates the wavelength overlays for the EFM PMDs along with the CWDM grid.

1260

1270 1290 1490 1570

1300 1360 1400 1480

1000Base-BX10-D

1500 1580

CWDM-grid (1270, 1290, ..., 1610, 1630 nm)

100Base-LX101000Base-LX-10

1000Base-BX10-U

O-band (1260–1360 nm) E-band (1360–1460 nm) S-band (1460–1530 nm) C-band(1530–1565 nm)

L-bandU-band

Figure 9: Wavelength Overlays and their Relation to EFMF

ConclusionThe EFM point-to-point technologies are extremely close to existing Ethernet, and its topology provides cost-effective opportunities for replacing expensive T1 and T3 links.

EFMF is a proven concept, and it is already being deployed in its pre-standard form. Typical applications are FTTH, FTTB/C, point-to-point end-to-end support for business access, and point-to-point aggregation.


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© Copyright 2006 Fujitsu Network Communications Inc. All Rights Reserved.FUJITSU (and design)® and THE POSSIBILITIES ARE INFINITE™ are trademarks of Fujitsu Limited. All other trademarks are the property of their respective owners.

Acronym Descriptor

C Celsius

CO Central Office

CSMA/CD Carrier Sense Multiple Access/Collision Detection

Cu Copper

CWDM Coarse Wavelength Division Multiplexing

EFM Ethernet in the First Mile

EFMC Ethernet in the First Mile over Copper

EFMF Ethernet in the First Mile over Fiber

FTTB/C Fiber to the Building/Curb

FTTH Fiber to the Home

IEEE Institute of Electrical and Electronics Engineers

GMII Gigabit Media Independent Interface

LAN Local Area Network


Mbps Megabits per Second

MDI Medium Dependent Interface

MII Media Independent Interface

MMF Multi Mode Fiber

OAM Operations, Administration and Maintenance

OSI Open Systems Interconnection

PCS Physical Coding Sublayer

PHY Physical Layer Device

PMA Physical Medium Attachment

PMD Physical Medium Dependent

SHDSL Symmetric High-Data-Rate Digital Subscriber Line

SMF Single Mode Fiber

VDSL Very-High-Data-Rate Digital Subscriber Line

WDM Wavelength Division Multiplexing

ethernet in the first mile over point-to-point fiber … in the first mile over point-to-point fiber...

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