ON THIS PAGE
EX4600 Network Cable and Transceiver Planning
Determining Interface Support for an EX4600 Switch
The 24 small form-factor pluggable (SFP) network ports on EX4600 switches support 10-Gigabit Ethernet transceivers and direct-attach copper (DAC) cables. The switch also supplies four quad small form-factor pluggable plus (QSFP+) ports for use as uplinks. These 40-Gigabit Ethernet ports support QSFP+ transceivers, QSFP+ DAC cables, and DAC breakout cables (DACBO). Each QSFP+ port on an EX4600 switch can be configured to operate as 10-Gigabit Ethernet interface by using a breakout cable or as a single 40-Gigabit Ethernet interface. The ports on an EX4600 switch are disabled by default. You enable a port through the CLI.
Figure 1 shows the different ports available on the EX4600 switch.
1 — Electrostatic discharge (ESD) terminal | 3 — 40 GbE ports (4) |
2 — 10 G ports (24) | 4 — Expansion module bays with cover panels (2) |
You can find information about the optical transceivers supported on your Juniper device by using the Hardware Compatibility Tool. In addition to transceiver and connection type, the optical and cable characteristics–where applicable–are documented for each transceiver. The Hardware Compatibility Tool enables you to search by product, displaying all the transceivers supported on that device, or category, by interface speed or type. The list of supported transceivers for the EX4600 is located at https://pathfinder.juniper.net/hct/product/#prd=EX4600.
The Juniper Networks Technical Assistance Center (JTAC) provides complete support for Juniper-supplied optical modules and cables. However, JTAC does not provide support for third-party optical modules and cables that are not qualified or supplied by Juniper Networks. If you face a problem running a Juniper device that uses third-party optical modules or cables, JTAC may help you diagnose host-related issues if the observed issue is not, in the opinion of JTAC, related to the use of the third-party optical modules or cables. Your JTAC engineer will likely request that you check the third-party optical module or cable and, if required, replace it with an equivalent Juniper-qualified component.
Use of third-party optical modules with high-power consumption (for example, coherent ZR or ZR+) can potentially cause thermal damage to or reduce the lifespan of the host equipment. Any damage to the host equipment due to the use of third-party optical modules or cables is the users’ responsibility. Juniper Networks will accept no liability for any damage caused due to such use.
Cable Specifications for QSFP+ Transceivers on EX4600 Series Switches
The 40-Gigabit Ethernet QSFP+ transceivers that are used in EX Series switches use 12-ribbon multimode fiber crossover cables with socket MPO/UP, MPO/UPC, or MPO/APC connectors. The fiber can be either OM3 or OM4. These cables are not sold by Juniper Networks.
To maintain agency approvals, use only a properly constructed, shielded cable.
Ensure that you order cables with the correct polarity. Vendors refer to these crossover cables as key up to key up, latch up to latch up, Type B, or Method B. If you are using patch panels between two QSFP+, ensure that the proper polarity is maintained through the cable plant.
Table 1 describes the signals on each fiber. Table 2 shows the pin-to-pin connections for proper polarity.
Fiber |
Signal |
|---|---|
1 |
Tx0 (Transmit) |
2 |
Tx1 (Transmit) |
3 |
Tx2 (Transmit) |
4 |
Tx3 (Transmit) |
5 |
Unused |
6 |
Unused |
7 |
Unused |
8 |
Unused |
9 |
Rx3 (Receive) |
10 |
Rx2 (Receive) |
11 |
Rx1 (Receive) |
12 |
Rx0 (Receive) |
Pin |
Pin |
|---|---|
1 |
12 |
2 |
11 |
3 |
10 |
4 |
9 |
5 |
8 |
6 |
7 |
7 |
6 |
8 |
5 |
9 |
4 |
10 |
3 |
11 |
2 |
12 |
1 |
Network Cable Specifications for EX4600 Switches
EX4600 switches have interfaces that use various types of network cables.
Table 3 lists the specifications for the cables that connect the console (CON) and management (MGMT) ports to management devices.
The EX4600 can be configured with SFP management ports that support 1000BASE-SX transceivers.
Ports on EX4600 Switches |
Cable Specification |
Cable/Wire Required |
Maximum Length |
Switch Receptacle |
Additional Information |
|---|---|---|---|---|---|
RJ-45 Console (CON) port |
RS-232 (EIA-232) serial cable |
One 7-foot (2.13-meter) length RJ-45 patch cable and RJ-45 to DB-9 adapter |
7 ft (2.13 m) |
RJ-45 |
Connect a Device to a Management Console Using an RJ-45 Connector |
Management (MGMT) Ethernet port (10/100/1000) |
Category 5 cable or equivalent suitable for 1000BASE-T operation |
One 7-foot (2.13-meter) length RJ-45 patch cable |
328 feet (100 meters) |
RJ-45 |
Overview of EX Series Switches: Fiber-Optic Cable Signal Loss, Attenuation, and Dispersion
To determine the power budget and power margin needed for fiber-optic connections, you need to understand how signal loss, attenuation, and dispersion affect transmission. EX Series switches use various types of network cables, including multimode and single-mode fiber-optic cable.
- Signal Loss in Multimode and Single-Mode Fiber-Optic Cable
- Attenuation and Dispersion in Fiber-Optic Cable
Signal Loss in Multimode and Single-Mode Fiber-Optic Cable
Multimode fiber is large enough in diameter to allow rays of light to reflect internally (bounce off the walls of the fiber). Interfaces with multimode optics typically use LEDs as light sources. However, LEDs are not coherent light sources. They spray varying wavelengths of light into the multimode fiber, which reflects the light at different angles. Light rays travel in jagged lines through a multimode fiber, causing signal dispersion. When light traveling in the fiber core radiates into the fiber), higher-order mode loss (HOL) occurs. (Cladding consists of layers of lower-refractive index material in close contact with a core material of higher refractive index.) Together, these factors reduce the transmission distance of multimode fiber compared to that of single-mode fiber.
Single-mode fiber is so small in diameter that rays of light reflect internally through one layer only. Interfaces with single-mode optics use lasers as light sources. Lasers generate a single wavelength of light, which travels in a straight line through the single-mode fiber. Compared to multimode fiber, single-mode fiber has a higher bandwidth and can carry signals for longer distances. Single-mode fiber is consequently more expensive than multimode fiber.
Exceeding the maximum transmission distances can result in significant signal loss, which causes unreliable transmission.
Attenuation and Dispersion in Fiber-Optic Cable
An optical data link functions correctly provided that modulated light reaching the receiver has enough power to be demodulated correctly. Attenuation is the reduction in strength of the light signal during transmission. Passive media components such as cables, cable splices, and connectors cause attenuation. Although attenuation is significantly lower for optical fiber than for other media, it still occurs in both multimode and single-mode transmissions. An efficient optical data link must transmit enough light to overcome attenuation.
Dispersion is the spreading of the signal over time. The following two types of dispersion can affect signal transmission through an optical data link:
-
Chromatic dispersion, which is the spreading of the signal over time caused by the different speeds of light rays
-
Modal dispersion, which is the spreading of the signal over time caused by the different propagation modes in the fiber
For multimode transmission, modal dispersion usually limits the maximum bit rate and link length. Chromatic dispersion or attenuation is not a factor.
For single-mode transmission, modal dispersion is not a factor. However, at higher bit rates and over longer distances, chromatic dispersion limits the maximum link length.
An efficient optical data link must have enough light to exceed the minimum power that the receiver requires to operate within its specifications. In addition, the total dispersion must be within the limits specified for the type of link in Telcordia Technologies document GR-253-CORE (Section 4.3) and International Telecommunications Union (ITU) document G.957.
When chromatic dispersion is at the maximum allowed, you can consider its effect as a power penalty in the power budget. The optical power budget must allow for the sum of component attenuation, power penalties (including those from dispersion), and a safety margin for unexpected power loss.
Calculate the Fiber-Optic Cable Power Budget for EX Series Devices
To ensure that fiber-optic connections have sufficient power for correct operation, calculate the link's power budget when planning fiber-optic cable layout and distances. This planning helps you ensure that fiber-optic connections have sufficient power for correct operation. The power budget is the maximum amount of power the link can transmit. When you calculate the power budget, you use a worst-case analysis to provide a margin of error. You use a worst-case analysis even though not all the parts of an actual system operate at the worst-case levels.
To calculate the worst-case estimate for a fiber-optic cable power budget (PB) for the link:
Calculating the Fiber-Optic Cable Power Margin for EX Series Devices
Before calculating the power margin, calculate the power budget (see Calculating the Fiber-Optic Cable Power Budget for EX Series Devices).
Calculate the link's power margin when planning fiber-optic cable layout and distances to ensure that fiber-optic connections have sufficient signal power to overcome system loss and still satisfy the minimum input requirements of the receiver for the required performance level. The power margin (PM) is the amount of power available after you subtract attenuation or link loss (LL) from the power budget (PB).
When you calculate the power margin, you use a worst-case analysis to provide a margin of error, even though not all parts of an actual system operate at worst-case levels. A power margin (PM ) greater than zero indicates that the power budget is sufficient to operate the receiver and that it does not exceed the maximum receiver input power. This means that the link will work. A (PM) that is zero or negative indicates insufficient power to operate the receiver. See the specification for your receiver to find the maximum receiver input power.
To calculate the worst-case estimate for the power margin (PM) for the link: