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PTX10000 Transceiver and Cable Specifications

 

Review fiber-optic cable characteristics and plan the power budget and power margin for fiber-optic cables connected to your device by using the information in the following topics:

PTX10000 Optical Transceiver and Cable Support

The PTX10008 router has eight slots for the line cards that can support a maximum of 1152 ports as 10-Gigabit Ethernet ports, 288 ports as 40-Gigabit Ethernet ports, or 240 ports as 100-Gigabit Ethernet ports. Each of the network ports on the port panel supports quad small form-factor pluggable plus (QSFP+) transceivers. PTX10016 has 16 slots for the line cards that can support a maximum of 2304 as 10-Gigabit Ethernet ports, 576 ports as 40-Gigabit Ethernet ports, or 480 ports as 100-Gigabit Ethernet ports. See PTX10K-LC1101 Line Card and PTX10K-LC1102 Line Card for more information about the network ports.

The network ports on the PTX10008 and PTX10016 support QSFP+ and QSFP28 transceivers.

You can find information about the pluggable transceivers supported on your Juniper Networks device by using the Hardware Compatibility Tool. In addition to transceiver and connector 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 PTX10008 is located at https://pathfinder.juniper.net/hct/product/#prd=PTX10008. The list of supported transceivers for the PTX10016 is located at https://pathfinder.juniper.net/hct/product/#prd=PTX10016.

Caution

If you face a problem running a Juniper Networks device that uses a third-party optic or cable, the Juniper Networks Technical Assistance Center (JTAC) can help you diagnose the source of the problem. Your JTAC engineer might recommend that you check the third-party optic or cable and potentially replace it with an equivalent Juniper Networks optic or cable that is qualified for the device.

PTX10000 Cable Specifications for Console and Management Connections

Table 1 lists the specifications for the cables that connect the PTX10000 line of routers to a management device.

Note

The PTX10000 models can be configured with SFP management ports that support 1000BASE-SX transceivers.

Table 1: Cable Specifications for Console and Management Connections for the PTX10000 Line of Routers

Port on PTX10000 Router

Cable Specification

Cable Supplied

Maximum Length

Device Receptacle

Console port

RS-232 (EIA-232) serial cable

One 7-foot (2.13-meter) long RJ-45 patch cable and RJ-45 to DB-9 adapter

7 feet (2.13 meters)

RJ-45

Management port

Category 5 cable or equivalent suitable for 1000BASE-T operation

One 7-foot (2.13-meter) long RJ-45 patch cable

328 feet (100 meters)

RJ-45

Understanding PTX10000 Series 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. The PTX10000 Series uses various types of network cables, including multimode and single-mode fiber-optic cables.

Signal Loss in Multimode and Single-Mode Fiber-Optic Cables

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 reflect 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 cladding (layers of lower refractive index material in close contact with a core material of higher refractive index), higher-order mode loss occurs. 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. It is consequently more expensive.

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 transmission. 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, rather than chromatic dispersion or attenuation, usually limits the maximum bit rate and link length. 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 the 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, its effect can be considered 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 losses.

Calculating the Fiber-Optic Cable Power Budget for a PTX10000 Router

Calculate the link's power budget when planning fiber-optic cable layout and distances to 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, even though all the parts of an actual system do not operate at the worst-case levels.

To calculate the worst-case estimate for the 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). For example, here, (PT) and (PR) are measured in decibels, and decibels are referenced to 1 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 a PTX10000 Router

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 losses 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 attenuation or link loss (LL) has been subtracted 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 all the parts of an actual system do not 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 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.

Before you begin to calculate the power margin:

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 2 (here, the link is 2 km long and multimode, and the (PB) is 13 dBm).

    Link-Loss Factor

    Estimated Link Loss Value

    Sample Link Loss (LL) Calculation Values

    Higher-order mode losses

    Multimode—0.5 dBm

    0.5 dBm

    Single-mode—None

    0 dBm

    Modal and chromatic dispersion

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

    0 dBm

    Single-mode—None

    0 dBm

    Connector

    0.5 dBm

    This example assumes five connectors. Loss for five connectors: 5 (0.5 dBm) = 2.5 dBm.

    Splice

    0.5 dBm

    This example assumes two splices. Loss for two splices: 2 (0.5 dBm) = 1 dBm.

    Fiber attenuation

    Multimode—1 dBm/km

    This example assumes the link is 2 km long. Fiber attenuation for 2 km: 2 km (1 dBm/km) = 2 dBm.

    Single-mode—0.5 dBm/km

    This example assumes the link is 2 km long. Fiber attenuation for 2 km: 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 specifications for your receiver to find the maximum receiver input power.