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This chapter describes the PA-GE port adapter and contains the following sections:
The PA-GE (see Figure 1-1) is a single-port port adapter that, when combined with the appropriate optical fiber cable and a Gigabit Interface Converter (GBIC), provides one Gigabit Ethernet (GE) interface that is compliant with the IEEE 802.3z specification. The GE interface on a PA-GE operates in full-duplex mode.
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Note The PA-GE offers an additional choice of high-speed LAN connection to Cisco 7200 VXR and Cisco uBR7246 VXR routers. The PA-GE does not offer wire rate performance on Cisco 7200 VXR or Cisco uBR7246 VXR routers but does offer performance throughput suitable to WAN aggregation applications. Cisco 7200 VXR and Cisco uBR7246 VXR routers---when deployed as WAN aggregation routers---can be integrated into a Gigabit Ethernet campus backbone using the PA-GE. |
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Note The PA-GE assembly is a field-replaceable unit (FRU). The GBIC is a separate FRU. |
This section provides an overview of the IEEE 802.3z specification and Gigabit Ethernet. The term Ethernet is commonly used for all LANs that generally conform to Ethernet specifications, including Gigabit Ethernet under IEEE 802.3z, which is well suited to applications in which a local communication medium must carry sporadic, occasionally heavy traffic at high peak data rates.
The IEEE 802.3z specification includes the following three physical layer protocols:
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Note Cisco Systems offers another version of 1000BaseLX called Long Haul (LH), which complies with the IEEE 802.3z 1000BaseLX specification but extends the transmission distance up to 6.21 miles (10 km). The PA-GE provides connection options for 1000BaseSX, 1000BaseLX, and Long Haul. The PA-GE does not support the 1000BaseCX physical layer protocol. |
Each physical layer protocol has a name that summarizes its characteristics in the format speed/signaling method/segment length, where speed is the LAN speed in megabits per second (Mbps), signaling method is the signaling method used (either baseband or broadband), and segment length is typically the maximum length between stations in hundreds of meters. For example, 1000BaseSX specifies a 1000-Mbps baseband LAN, with maximum network segments (operating distances) as defined in Table 1-1. Table 1-2 and Table 1-3 define maximum network segments for 1000BaseLX and Long Haul, respectively.
The PA-GE supports the following features:
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Note For information about specific software and hardware requirements for the PA-GE, see the "Software and Hardware Requirements" section. |
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Note The PA-GE does not support half-duplex operation; it supports only full-duplex operation. |
This section provides information about Gigabit Ethernet interface specifications, which include interface distance limitations, power budget and how to evaluate it, and optical fiber characteristics.
The PA-GE uses two types of optical fiber: single-mode and multimode. Modes can be thought of as bundles of light rays entering the fiber at a particular angle. Single-mode fiber allows only one mode of light to propagate through the fiber, whereas multimode fiber allows multiple modes of light to propagate through the fiber.
Multiple modes of light propagating through the fiber travel different distances depending on the entry angles, which cause them to arrive at the destination at different times (a phenomenon called modal dispersion). Single-mode fiber is capable of higher bandwidth and greater cable run distances than multimode fiber.
According to the IEEE 802.3z specification, power budget is defined as the minimum optical power available to overcome the sum of attenuation plus power penalties of the optical path between the transmitter and receiver calculated as the difference between the transmitter launch power (minimum) and the receiver power (minimum). Further, channel insertion loss is defined as the static loss of a link between a transmitter and a receiver. It includes the loss of the fiber, connectors, and splices, and it is used to calculate link distance.
Finally, for fiber-optic links, the power penalties of a link are not attributes of link attenuation. Power penalties include modal noise, relative intensity noise (RIN), intersymbol interference (ISI), mode partition noise, extinction ratio, and eye-opening penalties.
The following tables list worst-case power budgets and penalties by interface type:
Table 1-4 lists optical fiber cable characteristics. Table 1-5 lists minimum and maximum receive and transmit power parameters by transmission and optical fiber type.
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Note If the distance between two connected stations is greater than the maximum distances listed, significant signal loss can result, making transmission unreliable. The minimum distance between two connected stations is 6.56 feet (2 meters). A mode conditioning patch cord is needed for 1000BaseLX and 1000BaseLH multimode connections if these connections are greater than 984.25 feet (300 meters). (For information on the mode conditioning patch cord, see the "Mode Conditioning Patch Cord with a Multimode GBIC-LX and GBIC-LH" section.) |
| Parameter1 | 62.5-micron2 Multimode | 50-micron Multimode | ||
|---|---|---|---|---|
Modal bandwidth as measured at 850 nm (minimum, overfilled launch) | 160 MHz*km | 200 MHz*km | 400 MHz*km | 500 MHz*km |
Link power budget | 7.5 dB | 7.5 dB | 7.5 dB | 7.5 dB |
Operating distance | 721.78 feet (ft.) | 902.23 ft. | 1,640.42 ft. | 1,804.46 ft. |
2.38 dB | 2.60 dB | 3.37 dB | 3.56 dB | |
Link power penalties4 | 4.27 dB | 4.29 dB | 4.07 dB | 3.57 dB |
Unallocated margin in link power budget4 | 0.84 dB | 0.60 dB | 0.05 dB | 0.37 dB |
| 1Link penalties are used for link budget calculations. They are not requirements and are not meant to be tested. 210-6 meters (or 1 micrometer) = 1 micron. 3Operating distances used to calculate the channel insertion loss are the maximum values. 4A wavelength of 830 nm is used to calculate channel insertion loss, link power penalties, and unallocated margin. |
| Parameter1 | 62.5-micron2 Multimode | 50-micron Multimode | 10-micron Single-Mode | |
|---|---|---|---|---|
Modal bandwidth as measured at 1300 nm (minimum, overfilled launch) | 500 MHz*km | 400 MHz*km | 500 MHz*km | --- |
Link power budget | 7.5 dB | 7.5 dB | 7.5 dB | 8.0 dB |
Operating distance | 1,804.46 feet (ft.) | 1,804.46 ft. | 1,804.46 ft. | 16,404.20 ft. |
2.35 dB | 2.35 dB | 2.35 dB | 4.57 dB | |
Link power penalties4 | 3.48 dB | 5.08 dB | 3.96 dB | 3.27 dB |
Unallocated margin in link power budget4 | 1.67 dB | 0.07 dB | 1.19 dB | 0.16 dB |
| Parameter1 | 10-micron2 Single-Mode |
|---|---|
Link power budget | 10.5 dB |
Operating distance | 32,808.4 feet (ft.) |
7.8 dB | |
Link power penalties4 | 2.5 dB |
Unallocated margin in link power budget4 | 0.2 dB |
| Description | 62.5-micron1 Multimode | 50-micron Multimode | 10-micron Single-Mode | ||
|---|---|---|---|---|---|
Nominal fiber specification wavelength | 850 nm2 | 1300 nm | 850 nm | 1300 nm | 1300 nm |
Fiber cable attenuation (maximum) | 3.75 dB/km3 | 1.5 dB/km | 3.5 dB/km | 1.5 dB/km | 0.5 dB/km |
Modal bandwidth | 160 MHz*km | 500 MHz*km | 400 MHz*km | 400 MHz*km | --- |
200 MHz*km | 500 MHz*km | 500 MHz*km | 500 MHz*km | --- | |
Zero dispersion wavelength | 1320-1365 nm | 1295-1320 nm | 1300-1324 nm | ||
| 110-6 meters (or 1 micrometer) = 1 micron. 2nm = nanometers 3dB/km = decibels per kilometer |
| Transmission Type and Optical Fiber Type | Wavelength | Transmit Power Minimum/Maximum | Receive Power Minimum/Maximum |
|---|---|---|---|
1000BaseSX | | | |
1000BaseLX | | | |
Long Haul | | | |
| 110-6 meters (or 1 micrometer) = 1 micron 2nm = nanometers 3dBm = decibels per milliwatt |
To design an efficient optical data link, you should evaluate the power budget. Proper operation of an optical data link depends on modulated light reaching the receiver with enough power to be correctly demodulated. Data link efficiency is affected by the losses introduced by splices and connectors.
The maximum operating distance listed in Table 1-1, Table 1-2, and Table 1-3 is an estimate and is based on the following assumptions:
Therefore, for a real network, you could adjust the operating distance as follows:
You should note that exceeding the maximum operating distance is only feasible with single-mode optical fiber, not with multimode optical fiber (because of the penalty of the differential mode delay [DMD] associated with a laser source over multimode fiber). In all applications, we strongly recommend that you follow operating distance guidelines.
Power margin (PM) is defined as channel insertion loss or cable loss (connector loss + splice loss). The result should be greater than or equal to 0 and is expressed in decibels (dB).
The following is an example of a power margin (PM) calculation for a 1000BaseSX PA-GE over multimode optical fiber, based on the following variables:
Estimate the multimode power margin as follows:
From Table 1-1, the channel insertion loss is 2.60 dB, so
The positive value 0.16 dB indicates that this link has sufficient power for transmission.
The following example of PM for a Long-Haul PA-GE over a single-mode optical fiber is based on two buildings, 5 kilometers apart (with a loss of 0.5 dB/km; see Table 1-4), connected through a patch panel in an intervening building with a total of 10 connectors (each with a loss of 0.5 dB).
Estimate the single-mode power margin as follows:
From Table 1-3, the channel insertion loss is 7.8 dB, so
The positive value of 0.3 dB indicates that this link has sufficient power for transmission.
Statistical models more accurately determine the power budget than the worst-case method. Determining the link loss with statistical methods requires accurate knowledge of variations in the data link components. Statistical power budget analysis is beyond the scope of this publication. For further information, refer to ITU-T standards and your equipment specifications.
The following publications contain information on determining attenuation and power budget:
The PA-GE contains the enabled LED for the port adapter and a bank of three status LEDs for the GE interface. (The LEDs are shown in Figure 1-2.)
After system initialization, the enabled LED goes on to indicate that the PA-GE has been enabled for operation.
The following conditions must be met before the enabled LED goes on:
If any of these conditions is not met, or if the initialization fails for other reasons, the enabled LED does not go on.
Table 1-6 lists LED colors and indications.
| LED1 | Color | State | Indications |
|---|---|---|---|
Transmit (TX) | Green | Flickering on | Data is being transmitted. |
Receive (RX) | Green | Flickering on | Data is being received. |
Green | On | Interface is receiving a carrier signal from the network. |
| 1If no cable is connected to the GBIC, or a GBIC is not installed, the TX, RX, and LINK LEDs blink on and off in sequence. |
This section provides information about the cables and connectors you must use with the PA-GE.
This section provides information about cabling and connectors for the Gigabit Interface Converter (GBIC) (see Figure 1-3), which is a required component with the PA-GE and is installed between your PA-GE and your 1000BaseX-based network.
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Caution To prevent system problems, do not use GBICs from third-party vendors. Use only the GBIC that shipped with your PA-GE. |
The 1000BaseSX (GBIC-SX), 1000BaseLX (GBIC-LX), and Long-Haul (GBIC-LH) GBICs have one optical interface in the form of an SC-type duplex receptacle that supports IEEE 802.3z interfaces compliant with the 1000BaseX standard. (See Figure 1-3.)
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Note The PA-GE ships with a GBIC installed. The PA-GE assembly is a field-replaceable unit (FRU). The GBIC is a separate FRU. |
Depending on the GBIC you plan to use, it contains either a Class 1 laser of 850 nm for 1000BaseSX (short-wavelength) applications, a Class 1 laser of 1300 nm for 1000BaseLX (long-wavelength) applications, or a Class 1 laser of 1300 nm for Long Haul (long-wavelength) applications.
This section provides information about the optical fiber cables you should use with the PA-GE. Figure 1-4 and Figure 1-5 show the simplex and duplex SC-type connectors on your multimode or single-mode optical fiber cables. For simplex connections, one cable is required for transmit (TX) and a second cable is required for receive (RX). For duplex connections, one duplex connection is required for TX and RX. You can use either simplex or duplex connections for the PA-GE. (Optical fiber cables are commercially available; they are not available from Cisco Systems.)
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Warning Because invisible laser radiation may be emitted from the aperture of the port when no fiber cable is connected, avoid exposure to laser radiation, and do not stare into open apertures. |
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Warning Class 1 laser product. |
The optical fiber cables you must use with the GBIC on a PA-GE are as follows:
Both the GBIC-LX and the GBIC-LH option for the PA-GE have a 1300-nm (long-wavelength) Class 1 laser as a light source and provide a connection to 50/125-micron or 62.5-micron multimode optical fiber.
When an unconditioned laser source designed for operation on single-mode optical fiber is directly coupled to a multimode optical fiber cable, an effect known as differential mode delay (DMD) might result in a degradation of the modal bandwidth of the optical fiber cable.
This degradation results in a decrease in the link span (the distance between a transmitter and a receiver) that can be supported reliably. The effect of DMD can be overcome by conditioning the launch characteristics of a laser source. A practical means of performing this conditioning is to use a device called a mode conditioning patch cord.
A mode conditioning patch cord is an optical fiber cable assembly that consists of a pair of optical fibers terminated with connector hardware. Figure 1-6 shows a diagram of the mode conditioning patch cord assembly. Specifically, the mode conditioning patch cord is composed of a single-mode optical fiber permanently coupled off center to a graded-index multimode optical fiber. (See Offset in Figure 1-6.)
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Note The mode conditioning patch cord is not required with 1000BaseSX multimode connections or 1000BaseLX single-mode or Long Haul single-mode connections. |
The mode conditioning patch cord assembly is composed of duplex optical fibers, including a single-mode-to-multimode offset launch fiber connected to the transmitter, and a second conventional graded-index multimode optical fiber connected to the receiver. The use of a plug-to-plug patch cord maximizes the power budget of multimode 1000BaseLX and LH links.
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Caution If you plan to use a GBIC-LX or a GBIC-LH in your PA-GE at distances greater than 984.25 feet (300 meters) over 50/125-micron or 62./125-micron multimode fiber, to prevent data transmission problems you must use the mode conditioning patch cord. Do not use the procedure in this section. Instead, proceed to the "Attaching a Mode Conditioning Patch Cord to a GBIC-LX or GBIC-LH" section. |
A typical application of a mode conditioning patch cord is shown in Figure 1-7.
This section describes the port adapter slot numbering for the platforms that support the PA-GE.
Figure 1-8 shows a Cisco 7206VXR with port adapters installed. In the Cisco 7206VXR, port adapter slot 1 is in the lower left position, and port adapter slot 6 is in the upper right position. (The four-slot Cisco 7204VXR is not shown.) However, the PA-GE can be installed in any available port adapter slot except port adapter slot 0, which is reserved for the I/O controller for the Fast Ethernet port (if present) on the Cisco 7200 VXR routers.
Figure 1-9 shows a Cisco uBR7246 VXR router with installed port adapters. Slot 0 is reserved for the I/O controller. You can install a PA-GE port adapter in either slot 1 or slot 2 of a Cisco uBR7246 VXR.
This section describes how to identify interface addresses for the PA-GE in supported platforms. Interface addresses specify the actual physical location of each interface on a router or switch.
Interfaces on the PA-GE installed in a Cisco 7200 VXR or Cisco uBR7246 VXR router maintain the same address regardless of whether other port adapters are installed or removed. However, when you move a port adapter to a different slot, the first number in the interface address changes to reflect the new port adapter slot number.
Table 1-7 explains how to identify interface addresses.
| Platform | Interface | Numbers | Syntax |
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Cisco 7200 VXR routers | Port-adapter-slot-number/interface-port-number | Port adapter slot---0 through 6 (depends on the number of slots in the router)1 Interface port---always 0 | 1/0 |
Cisco uBR7246 VXR routers | Port-adapter-slot-number/interface-port-number
| Port adapter slot-always 1 or 2 Interface port-always 0 | 1/0 |
| 1Port adapter slot 0 is reserved for the Fast Ethernet port on the I/O controller (if present). |
This section describes how to identify the interface address used for the PA-GE in Cisco 7200 VXR routers.
The interface address is composed of a two-part number in the format port-adapter-slot-number/interface-port-number. See Table 1-7 for the interface address format.
In Cisco 7200 VXR routers, port adapter slots are numbered from the lower left to the upper right, beginning with port adapter slot 1 (lower left) and continuing through port adapter slot 4 for the Cisco 7204VXR and slot 6 for the Cisco 7206VXR. (Port adapter slot 0 is reserved for the optional Fast Ethernet port on the I/O controller---if present.)
The interface address of the GE interface on a PA-GE in port adapter slot 1 is 1/0 (port adapter slot 1 and interface 0). If the PA-GE was in port adapter slot 4, this same interface would be numbered 4/0 (port adapter slot 4 and interface 0).
This section describes how to identify the interface address used for the PA-GE in Cisco uBR7246 VXR routers. The interface address is composed of a two-part number in the format port-adapter-slot-number/interface-port-number. See Table 1-7 for the interface address format.
In Cisco uBR7246 VXR routers, port adapter slots are numbered slot 1 and slot 2. (Slot 0 is always reserved for the Fast Ethernet port on the I/O controller---if present). The number of additional ports depends on the number of ports on a port adapter.
The interface address of the interface on a PA-GE in port adapter slot 2 is 2/0 (port adapter slot 2 and interface 0). If the PA-GE was in port adapter slot 1, this same interface would be numbered 1/0 (port adapter slot 1 and interface 0).
Posted: Mon May 22 08:21:47 PDT 2000
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