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PTX10003 Network Cable and Transceiver Planning

 

Determining Transceiver Support for the PTX10003

Each of the PTX10003 front panel interfaces support quad small-form factor pluggable (QSFP-DD) optical transceivers. The interfaces on a PTX10003 can be configured to support 10 Gbps, 40 Gbps, 100 Gbps, 200 Gbps, and 400 Gbps data rates.

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 PTX10003 routers is located at https://apps.juniper.net/hct/product/#prd=PTX10003.

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.

Cable and Connector Specifications for MX and PTX Series Devices

The transceivers that are supported on MX Series and PTX Series devices use fiber-optic cables and connectors. The type of connector and the type of fiber depends on the transceiver type.

You can determine the type of cable and connector required for your specific transceiver by using the Hardware Compatibility Tool.

Caution

To maintain agency approvals, use only a properly constructed, shielded cable.

Note

The terms multifiber push-on (MPO) and multifiber termination push-on (MTP) describe the same connector type. The rest of this topic uses MPO to mean MPO or MTP.

12-Fiber MPO Connectors

There are two types of cables used with 12-fiber MPO connectors on Juniper Networks devices—patch cables with MPO connectors on both ends, and breakout cables with an MPO connector on one end and four LC duplex connectors on the opposite end. Depending on the application, the cables might use single-mode fiber (SMF) or multimode fiber (MMF). Juniper Networks sells cables that meet the supported transceiver requirements, but it is not required to purchase cables from Juniper Networks.

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 transceivers, ensure that the proper polarity is maintained through the cable plant.

Also, ensure that the fiber end in the connector is finished correctly. Physical contact (PC) refers to fiber that has been polished flat. Angled physical contact (APC) refers to fiber that has been polished at an angle. Ultra physical contact (UPC) refers to fiber that has been polished flat, to a finer finish. The required fiber end is listed with the connector type in the Hardware Compatibility Tool.

12-Fiber Ribbon Patch Cables with MPO Connectors

You can use 12-fiber ribbon patch cables with female MPO connectors to connect two transceivers of the same type—for example, 40GBASE-SR4-to-40GBASESR4 or 100GBASE-SR4-to-100GBASE-SR4. You can also connect 4x10GBASE-LR or 4x10GBASE-SR transceivers by using patch cables—for example, 4x10GBASE-LR-to-4x10GBASE-LR or 4x10GBASE-SR-to-4x10GBASE-SR—instead of breaking the signal out into four separate signals.

Table 1 describes the signals on each fiber. Table 2 shows the pin-to-pin connections for proper polarity.

Table 1: Cable Signals for 12-Fiber Ribbon Patch Cables

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)

 

Table 2: Cable Pinouts for 12-Fiber Ribbon Patch Cables

MPO Pin

MPO 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

12-Fiber Ribbon Breakout Cables with MPO-to-LC Duplex Connectors

You can use 12-ribbon breakout cables with MPO-to-LC duplex connectors to connect a QSFP+ transceiver to four separate SFP+ transceivers—for example, 4x10GBASE-LR-to-10GBASE-LR or 4x10GBASE-SR-to-10GBASE-SR SFP+ transceivers. The breakout cable is constructed out of a 12-fiber ribbon fiber-optic cable. The ribbon cable splits from a single cable with a female MPO connector on one end, into four cable pairs with four LC duplex connectors on the opposite end.

Figure 1 shows an example of a typical 12-ribbon breakout cable with MPO-to-LC duplex connectors (depending on the manufacture, your cable may look different).

Figure 1: 12-Ribbon Breakout Cable
12-Ribbon Breakout Cable

Table 3 describes the way the fibers are connected between the MPO and LC duplex connectors. The cable signals are the same as those described in Table 1.

Table 3: Cable Pinouts for 12-Fiber Ribbon Breakout Cables

MPO Connector Pin

LC Duplex Connector Pin

1

Tx on LC Duplex 1

2

Tx on LC Duplex 2

3

Tx on LC Duplex 3

4

Tx on LC Duplex 4

5

Unused

6

Unused

7

Unused

8

Unused

9

Rx on LC Duplex 4

10

Rx on LC Duplex 3

11

Rx on LC Duplex 2

12

Rx on LC Duplex 1

12-Ribbon Patch and Breakout Cables Available from Juniper Networks

Juniper Networks sells 12-ribbon patch and breakout cables with MPO connectors that meet the requirements described above. It is not required to purchase cables from Juniper Networks. Table 4 describes the available cables.

Table 4: 12-Ribbon Patch and Breakout Cables Available from Juniper Networks

Cable Type

Connector Type

Fiber Type

Cable Length

Juniper Model Number

12-ribbon patch

Female MPO/PC to female MPO/PC, key up to key up

MMF (OM3)

1 m

MTP12-FF-M1M

3 m

MTP12-FF-M3M

5 m

MTP12-FF-M5M

10 m

MTP12-FF-M10M

Female MPO/APC to female MPO/APC, key up to key up

SMF

1 m

MTP12-FF-S1M

3 m

MTP12-FF-S3M

5 m

MTP12-FF-S5M

10 m

MTP12-FF-S10M

12-ribbon breakout

Female MPO/PC, key up, to four LC/UPC duplex

MMF (OM3)

1 m

MTP-4LC-M1M

3 m

MTP-4LC-M3M

5 m

MTP-4LC-M5M

10 m

MTP-4LC-M10M

Female MPO/APC, key up, to four LC/UPC duplex

SMF

1 m

MTP-4LC-S1M

3 m

MTP-4LC-S3M

5 m

MTP-4LC-S5M

10 m

MTP-4LC-S10M

24-Fiber MPO Connectors

You can use patch cables with 24-fiber MPO connectors to connect two supported transceivers of the same type—for example, 100GBASE-SR10-to-100GBASE-SR10.

Figure 2 shows the 24-fiber MPO optical lane assignments.

Figure 2: 24-Fiber MPO Optical Lane Assignments
24-Fiber MPO Optical Lane Assignments
Note

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 transceivers, ensure that the proper polarity is maintained through the cable plant.

The MPO optical connector for the CFP2-100G-SR10-D3 is defined in Section 5.6 of the CFP2 Hardware Specification and Section 88.10.3 of IEEE STD 802.3-2012. These specifications include the following requirements:

  • Recommended Option A in IEEE STD 802.3-2012.

  • The transceiver receptacle is male. A patch cable with female connector is required to mate with the module.

  • Ferrule finish shall be flat polished interface that is compliant with IEC 61754-7.

  • Alignment key is key up.

The optical interface must meet the requirement FT-1435-CORE in Generic Requirements for Multi-Fiber Optical Connectors. The module must pass the wiggle test defined by IEC 62150-3.

LC Duplex Connectors

You can use patch cables with LC duplex connectors to connect two supported transceivers of the same type—for example, 40GBASE-LR4-to-40GBASE-LR4 or 100GBASE-LR4-to100GBASE-LR4. The patch cable is one fiber pair with two LC duplex connectors at opposite ends. LC duplex connectors are also used with 12-fiber ribbon breakout cables, as described in 12-Fiber Ribbon Breakout Cables with MPO-to-LC Duplex Connectors.

Figure 3 shows an LC duplex connector being installed in a transceiver.

Figure 3: LC Duplex Connector
LC Duplex Connector

Understanding Fiber-Optic Cable Signal Loss, Attenuation, and Dispersion

This topic describes signal loss, 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 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 cladding, higher-order mode loss results. Together these factors limit the transmission distance of multimode fiber compared with single-mode fiber.

Single-mode fiber is so small in diameter that rays of light can 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 with multimode fiber, single-mode fiber has higher bandwidth and can carry signals for longer distances.

Exceeding the maximum transmission distances can result in significant signal loss, which causes unreliable transmission.

Attenuation and Dispersion in Fiber-Optic Cable

Correct functioning of an optical data link depends on modulated light reaching the receiver with enough power to be demodulated correctly. Attenuation is the reduction in power of the light signal as it is transmitted. Attenuation is caused by passive media components, such as cables, cable splices, and connectors. 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 have enough light available to overcome attenuation.

Dispersion is the spreading of the signal over time. The following two types of dispersion can affect an optical data link:

  • Chromatic dispersion—Spreading of the signal over time resulting from the different speeds of light rays.

  • Modal dispersion—Spreading of the signal over time resulting from 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 rather than modal dispersion limits 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 less than 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, 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 Power Budget and Power Margin for Fiber-Optic Cables

Use the information in this topic and the specifications for your optical interface to calculate the power budget and power margin for fiber-optic cables.

Tip

You can use the Hardware Compatibility Tool to find information about the pluggable transceivers supported on your Juniper Networks device.

To calculate the power budget and power margin, perform the following tasks:

  1. Calculating Power Budget for Fiber-Optic Cable

  2. Calculating Power Margin for Fiber-Optic Cable

Calculating Power Budget for Fiber-Optic Cable

To ensure that fiber-optic connections have sufficient power for correct operation, you need to calculate the link's power budget, which is the maximum amount of power it 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 of power budget (PB), you assume minimum transmitter power (PT) and minimum receiver sensitivity (PR):

PB = PT – PR

The following hypothetical power budget equation uses values measured in decibels (dB) and decibels referred to one milliwatt (dBm):

PB = PT – PR

PB = –15 dBm – (–28 dBm)

PB = 13 dB

Calculating Power Margin for Fiber-Optic Cable

After calculating a link's power budget, you can calculate the power margin (PM), which represents the amount of power available after subtracting attenuation or link loss (LL) from the power budget (PB). A worst-case estimate of PM assumes maximum LL:

PM = PB – LL

PM greater than zero indicates that the power budget is sufficient to operate the receiver.

Factors that can cause link loss include higher-order mode losses, modal and chromatic dispersion, connectors, splices, and fiber attenuation. Table 5 lists an estimated amount of loss for the factors used in the following sample calculations. For information about the actual amount of signal loss caused by equipment and other factors, refer to vendor documentation.

Link-Loss Factor

Estimated Link-Loss Value

Higher-order mode losses

Single mode—None

Multimode—0.5 dB

Modal and chromatic dispersion

Single mode—None

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

Connector

0.5 dB

Splice

0.5 dB

Fiber attenuation

Single mode—0.5 dB/km

Multimode—1 dB/km

The following sample calculation for a 2-km-long multimode link with a power budget (PB) of 13 dB uses the estimated values from Table 5 to calculate link loss (LL) as the sum of fiber attenuation (2 km @ 1 dB/km, or 2 dB) and loss for five connectors (0.5 dB per connector, or 2.5 dB) and two splices (0.5 dB per splice, or 1 dB) as well as higher-order mode losses (0.5 dB). The power margin (PM) is calculated as follows:

PM = PB – LL

PM = 13 dB – 2 km (1 dB/km) – 5 (0.5 dB) – 2 (0.5 dB) – 0.5 dB

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

PM = 7 dB

The following sample calculation for an 8-km-long single-mode link with a power budget (PB) of 13 dB uses the estimated values from Table 5 to calculate link loss (LL) as the sum of fiber attenuation (8 km @ 0.5 dB/km, or 4 dB) and loss for seven connectors (0.5 dB per connector, or 3.5 dB). The power margin (PM) is calculated as follows:

PM = PB – LL

PM = 13 dB – 8 km (0.5 dB/km) – 7(0.5 dB)

PM = 13 dB – 4 dB – 3.5 dB

PM = 5.5 dB

In both examples, the calculated power margin is greater than zero, indicating that the link has sufficient power for transmission and does not exceed the maximum receiver input power.