Fiber Jumpers

Overview

A fiber jumper consists of one or more optical fibers of a certain length and the optical connectors at both ends. A fiber jumper connects an optical module to a fiber terminal box.

Comply with the following rules when selecting fiber jumpers:

1. Determine the length of fiber jumpers based on the onsite cabling distance.

2. Determine the fiber type based on the optical module type.

   • Use a multimode fiber jumper for a multimode optical module.

   • Use a single-mode fiber jumper for a single-mode optical module.

3. Determine the optical connector type based on the port type.

   Ensure that the optical connector at each end of a fiber jumper is the same type as the port to which it will be connected.

The MPO-MPO fibers for CloudEngine series switches use type B connectors (key Up/key Up).

Appearance and Structure

Figure 7-20 shows the appearance of an LC single-mode fiber.

Figure 7-20 Appearance of an LC single-mode fiber

Figure 7-21 shows the appearance of an LC multimode fiber.

Figure 7-21 Appearance of an LC multimode fiber

Figure 7-22 shows the appearance of an MPO-MPO single-mode fiber.

Figure 7-22 Appearance of an MPO-MPO single-mode fiber

Figure 7-23 shows the appearance of an 8-core or 12-core MPO-MPO multi-mode fiber.

Figure 7-23 Appearance of an 8-core or 12-core MPO-MPO multi-mode fiber

Figure 7-24 shows the appearance of an MPO-4*DLC fiber.

Figure 7-24 Appearance of an MPO-4*DLC fiber

Pin Assignments

• Pin assignments of an 8-core MPO-MPO fiber
  Figure 7-25 Structure of an 8-core MPO-MPO fiber
  
  Table 7-13 Pin assignments of an 8-core MPO-MPO fiber

  X1 Pin	X2 Pin
  1	12
  2	11
  3	10
  4	9
  9	4
  10	3
  11	2
  12	1

• Pin assignments of a 12-core MPO-MPO fiber
  Figure 7-26 Structure of a 12-core MPO-MPO fiber
  
  Table 7-14 Pin assignments of a 12-core MPO-MPO fiber

  X1 Pin	X2 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

• Pin assignments of an MPO-4*DLC fiber
  Figure 7-27 Structure of an MPO-4*DLC fiber
  
  Table 7-15 Pin assignments of an MPO-4*DLC fiber

  X1 Pin	X2 Pin
  1	1B
  2	2B
  3	3B
  4	4B
  9	4A
  10	3A
  11	2A
  12	1A

Optical Fiber, Optical Connector, and Optical Distribution Frame

Optical Fiber

Optical fibers are classified into single-mode fibers and multimode fibers.

• Single-mode fibers have a diameter of 5 μm to 10 μm and transmit laser in a single mode with a specified wavelength. These fibers support a wide frequency band and a large transmission capacity, so they are used for long-distance transmission. Most single-mode fibers are yellow, as shown in Figure 7-20.

• Multimode fibers have a diameter of 50 μm or 62.5 μm and transmit laser in multiple modes with a specified wavelength. These fibers have a lower transmission capacity than single-mode fibers and are used for short-distance transmission. Model dispersion occurs during transmission over multimode fibers.

  In the latest cabling infrastructure of ISO/IEC 11801, multimode fibers are classified into four categories: OM1, OM2, OM3, and OM4.

  • OM1: traditional 62.5 μm/125 μm multimode fibers. OM1 fibers have a large core diameter and numerical aperture, and provide high light gathering ability and bending resistance.

  • OM2: traditional 50 μm/125 μm multimode fibers. OM2 fibers have a small core diameter and numerical aperture. Compared with OM1 fibers, OM2 fibers provide higher bandwidth because they significantly reduce the modal dispersion. When transmitting data at 1 Gbit/s with 850 nm wavelength, OM1 and OM2 fibers support maximum link lengths of 220 m and 550 m, respectively. OM1 and OM2 fibers can provide sufficient bandwidth within a distance of 300 m. Generally, OM1 and OM2 fibers are orange, as shown in Figure 7-21.

  • OM3: next-generation multimode fibers, with longer transmission distances than OM1 and OM2 fibers.

  • OM4: laser optimized multimode fibers with 50 μm core diameter. OM4 is an improvement to OM3 and only increases the modal bandwidth. OM4 fibers provide 4700 MHz*km of modal bandwidth, whereas OM3 fibers provide only 2000 MHz*km of modal bandwidth. Generally, OM3 and OM4 fibers are light green, as shown in Figure 7-23. You can identify OM3 and OM4 fibers by their labels or printed marks.

MPO fibers are used for 40GE and 100GE optical modules. An MPO fiber consists of multiple multimode fiber cores, and each multimode fiber core provides one laser transmission channel. MPO fibers may come in the following specifications: 8-core, 12-core, or 24-core.

• A 40GE optical module uses four channels to transmit laser and four channels to receive laser. That is, a total of eight channels are required for a 40GE optical module. 8-core and 12-core MPO fibers have the same definition of fiber channels. Therefore, they are equivalent in functionality when connecting to 40GE optical modules.

• When 100GE optical modules are used, choose MPO fibers according to the optical module form factor. Choose 8-core or 12-core fibers for QSFP28 optical modules with MPO connectors.

An optical module installed with optical fibers with LC connectors uses one channel to transmit laser and one channel to receive laser. That is, two channels are required for such an optical module. A single-fiber bidirectional optical module uses one channel to transmit and receive laser, and therefore only one channel is required.

Optical Connector

Optical connectors are used to connect optical fibers of the same type. Table 7-16 lists common optical connectors.

Figure 7-28 shows an LC/PC optical connector.

Figure 7-28 LC/PC optical connector

When connecting or removing an LC/PC optical connector, align the connector with the optical port and do not rotate the fiber. Pay attention to the following points:

• To connect a fiber, align the optical connector with the optical port and gently insert the optical fiber into the port.

• To remove a fiber, press the clip on the connector, push the connector inward slightly, and pull the fiber out.

Optical Distribution Frame

Optical ports of two switches are not directly connected by optical fibers. An optical distribution frame (ODF) is usually deployed between the two switches.

Figure 7-29 shows an example of MPO-4*DLC (1-to-4) fiber connection through an ODF. When connecting optical fibers between two devices, pay attention to the following points:

• Determine the fiber connector type (LC/FC) supported by the ODF and select appropriate fiber jumpers for the supported connector type.
• Fiber jumpers from the DC switches at both ends must be connected to the ODF at the same sequence.
• Each pair of Tx and Rx optical fibers must be cross-connected on the ODF to ensure normal transmission between the optical modules at both ends.

Figure 7-29 MPO-4*DLC (1-to-4) fiber connection through an ODF

Ceramic Ferrule End Face

Based on the return loss, the end faces of the fiber's ceramic ferrule are classified into three types: PC, UPC, and APC, as shown in Figure 7-30.

Figure 7-30 Polishing types of the fiber's ceramic ferrule end face

In principle, optical fibers with different ceramic ferrule end faces cannot be directly connected through optical connectors. Interconnection between PC and UPC connectors does not cause permanent physical damage to them. The structure of APC end faces is totally different from that of PC end faces. Therefore, if fibers with APC end faces and fibers with PC end faces are connected through optical connectors, their ceramic ferrule end faces will be damaged. To connect them together, use a fiber jumper. This, however, adversely affects the transmission performance.

Figure 7-31 shows the requirements of different types of ceramic ferrule end face of fibers.

Figure 7-31 Fiber's ceramic ferrule end faces