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EX4650 Network Cable and Transceiver Planning

Pluggable Transceivers Supported on EX4650 Switches

EX4650 switches support SFP, SFP+, and QSFP+ transceivers. You can find the list of transceivers supported on EX4650 switches and information about those transceivers at the Hardware Compatibility Tool page for EX4650.

Note:

We recommend that you use only optical transceivers and optical connectors purchased from Juniper Networks with your Juniper Networks device.

CAUTION:

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.

The Gigabit Ethernet SFP+, and QSFP+ transceivers installed in EX4650 switches support digital optical monitoring (DOM): You can view the diagnostic details for these transceivers by issuing the operational mode CLI command show interfaces diagnostics optics.

Note:

The transceivers support DOM even if they are installed in the SFP+ uplink module ports.

SFP28 Direct Attach Copper Cables for EX4650 Switches

Small form-factor pluggable transceiver (SFP28) direct attach copper (DAC) cables, also known as Twinax cables, are suitable for in-rack connections between servers and switches. They are suitable for short distances, making them ideal for highly cost-effective networking connectivity within a rack and between adjacent racks.

Note:

We recommend that you use only SFP28 DAC cables purchased from Juniper Networks with your Juniper Networks device.

CAUTION:

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

EX4650 switches support SFP28 passive DAC cables. The passive Twinax cable is a straight cable with no active electronic components. EX4650 switches support 1  m, 3  m, and 5  m long SFP28 passive DAC cables. See Figure 1.

Figure 1: SFP28 Direct Attach Copper Cables for EX4650 SwitchesSFP28 Direct Attach Copper Cables for EX4650 Switches

The cables are hot-removable and hot-insertable: You can remove and replace them without powering off the switch or disrupting switch functions. A cable comprises a low-voltage cable assembly that connects directly into two 25-Gigabit Ethernet ports, one at each end of the cable. The cables use high-performance integrated duplex serial data links for bidirectional communication and are designed for data rates of up to 25  Gbps.

Standards Supported by These Cables

The cables comply with the following standards:

QSFP28 Direct Attach Copper Cables for EX4650 Switches

Quad small form-factor pluggable (QSFP28) direct attach copper (DAC) cables are suitable for in-rack connections between QSFP28 ports on EX4650 switches. They are suitable for short distances, making them ideal for highly cost-effective networking connectivity within a rack and between adjacent racks.

Note:

We recommend that you use only QSFP28 DAC cables purchased from Juniper Networks with your Juniper Networks device.

CAUTION:

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

QSFP28 passive DAC cables are hot-removable and hot-insertable. A cable consists of a cable assembly that connects directly into two QSFP28 modules, one at each end of the cable. The cables use integrated duplex serial data links for bidirectional communication and are designed for data rates up to 100 Gbps. Passive DAC cables have no signal amplification built into the cable assembly. See Figure 2.

Figure 2: QSFP28 Direct Attach Copper CablesQSFP28 Direct Attach Copper Cables

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:

  1. Determine values for the link's minimum transmitter power (PT) and minimum receiver sensitivity (PR). In the following example, we measure both (PT) and (PR ) in decibels relative to one milliwatt (dBm).

    PT = – 15 dBm

    PR = – 28 dBm

    Note:

    See the specifications for your transmitter and receiver to find the minimum transmitter power and minimum receiver sensitivity.
  2. Calculate the power budget (PB) by subtracting (PR) from (PT):

    – 15 dBm – (–28 dBm) = 13 dBm

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:

  1. Determine the maximum value for link loss (LL) by adding estimated values for applicable link-loss factors—for example, use the sample values for various factors as provided in Table 1 (here, the link is 2 km long and multimode, and the (PB) is 13 dBm):
    Table 1: Estimated Values for Factors Causing Link Loss

    Link-Loss Factor

    Estimated Link-Loss Value

    Sample (LL) Calculation Values

    Higher-order mode losses (HOL)

    • Multimode—0.5 dBm

    • Single mode—None

    • 0.5 dBm

    • 0 dBm

    Modal and chromatic dispersion

    • Multimode—None, if product of bandwidth and distance is less than 500 MHz/km

    • Single mode—None

    • 0 dBm

    • 0 dBm

    Connector

    0.5 dBm

    This example assumes 5 connectors. Loss for 5 connectors:

    (5) * (0.5 dBm) = 2.5 dBm

    Splice

    0.5 dBm

    This example assumes 2 splices. Loss for two splices:

    (2) * (0.5 dBm) = 1 dBm

    Fiber attenuation

    • Multimode—1 dBm/km

    • Single mode—0.5 dBm/km

    This example assumes the link is 2  km long. Fiber attenuation for 2 km:

    • (2 km) * (1.0 dBm/km) = 2 dBm

    • (2 km) * (0.5 dBm/km) = 1 dBm

    Clock Recovery Module (CRM)

    1 dBm

    1 dBm
    Note:

    For information about the actual amount of signal loss caused by equipment and other factors, see your vendor documentation for that equipment.

  2. Calculate the (PM) by subtracting (LL) from (PB):

    PB – LL = PM

    (13 dBm) – (0.5 dBm [HOL]) – ((5) * (0.5 dBm)) – ((2) * (0.5 dBm)) – ((2 km) * (1.0 dBm/km)) – (1 dB [CRM]) = PM

    13 dBm – 0.5 dBm – 2.5 dBm – 1 dBm – 2 dBm – 1 dBm = PM

    PM = 6 dBm

    The calculated power margin is greater than zero, indicating that the link has sufficient power for transmission. Also, the power margin value does not exceed the maximum receiver input power. Refer to the specification for your receiver to find the maximum receiver input power.