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ACX7509 Transceiver Support and Network Cable Planning

SUMMARY Your transceiver and network cable plan for the ACX7509 router must take into consideration the fiber-optic cables you can use, including connector details and pinouts. For optimal router function, your site must meet cable power requirements and mitigate cable signal loss, attenuation, and dispersion.

Determining Transceiver Support for ACX7509

You can find information about the pluggable transceivers and connector types that your Juniper Networks router supports by using the Hardware Compatibility Tool. The tool also documents the optical and cable characteristics, where applicable, for each transceiver. You can search for transceivers by product—the tool displays all the transceivers supported on that device—or by category, interface speed, or type.

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 and Connector Specifications for ACX7509 Routers

The transceivers that the ACX7509 router supports 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 that your specific transceiver requires 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 either MPO or MTP.

12-Fiber MPO Connectors

Two types of cables are 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 socket MPO connectors to connect two transceivers of the same type—for example, 40GBASE-SR4-to-40GBASE-SR4 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 fiber-optic ribbon cable. The ribbon cable splits from a single cable with a socket MPO connector on one end into four cable pairs with four LC duplex connectors on the opposite end.

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

Socket MPO/PC to socket 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

Socket MPO/APC to socket 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

Socket 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

Socket 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 1 shows the 24-fiber MPO optical lane assignments.

Figure 1: 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 is required.

  • The transceiver receptacle is a plug. A patch cable with a socket connector is required to mate with the module.

  • Ferrule finish shall be a 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.

CS Connector

You can use patch cables with CS connectors to connect two supported transceivers of the same type—for example, 2x100G-LR4 to 2x100G-LR4 or 2x100G-CWDM4 to 2x100G-CWDM4. A CS connector is compact, designed for next-generation QSFP-DD transceivers. This type of connector provides easy backward compatibility with QSFP28 and QSFP56 transceivers.

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.

Figure 2 shows an LC duplex connector being installed in a transceiver.

Figure 2: LC Duplex Connector LC Duplex Connector

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:

Calculate Power Budget for Fiber-Optic Cables

To ensure that fiber-optic connections have sufficient power for correct operation, you need to calculate the link's power budget (PB), 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 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

How to Calculate Power Margin for Fiber-Optic Cables

After calculating a link's PB, you can calculate the power margin (PM), which represents the amount of power available after subtracting attenuation or link loss (LL) from the 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.

Table 5: Estimated Values for Factors Causing Link Loss

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

Faulty 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 PB of 13 dB uses the estimated values from Table 5. This example calculates 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 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 PB of 13 dB uses the estimated values from Table 5. This example calculates 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 pPM 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 the examples, the calculated PM is greater than zero, indicating that the link has sufficient power for transmission and does not exceed the maximum receiver input power.

Fiber-Optic Cable Signal Loss, Attenuation, and Dispersion

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 a 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.