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Optical Distribution System Architecture: Interconnect

Fiber Optic
Posted by James Donovan on 2 November 2016 Connect with James on LinkedIn Estimated reading time: 3 minutes

When configuring an Optical Distribution Frame (ODF), one of the first considerations is the decision between interconnect and cross-connect architectures. As with the location of optical components, this decision has large implications for the network’s future growth, reconfigurability, cost and reliability.

Interconnect Systems Architectures

Interconnect involves the OSP cable being spliced to a pre-connectorized pigtail, which in turn is terminated to the back of a termination panel. The front of the panel allows access to the OSP fiber via a patch cord that is routed to the ODF directly from the optical equipment (see Figure 1).

interconnect-systems-figure-1

(Figure 1)

In interconnect, the optical equipment fiber patch cord does not have a dedicated port location. When the distance between the ODF and the equipment rack is great, more than five meters, reconfiguring the network can be difficult.

If the patch cord routed from the equipment and the ODF is too short to reach the far end of the lineup, another patch cord may have to be run between the ODF and the equipment.

In large central office applications, this can take between 20 minutes and two weeks, depending on the layout of the office, the state of the cable raceway system, and the availability of a long enough patch cord (see Figure 2).

Also, any time a patch cord and corresponding fiber are moved, damage can occur. And if the patch cord is damaged during the rerouting, a new patch cord will have to be installed. These situations increase the time required to turn up new services or to reconfigure or restore existing services. This also increases network operating costs and can adversely affect customer service.

interconnect-systems-figure-2

(Figure 2)

In interconnect systems, the slack storage system is generally not thoroughly considered, exposing large numbers of fibers to potential macro-bending problems. Bend radius violations are common, and individual fiber access can be difficult.

The introduction of field-terminated connectors could eliminate any storage issues, but it would also mean that any network reconfiguration would require a new patch cord to be run between the ODF and the equipment. This would increase the congestion in the cable raceway between the frames, since the existing fibers would more than likely be left in place. The time required to reconfigure the network would also increase.

If no network reconfiguration is anticipated, an interconnect architecture can work; however, as network requirements change, the ability to reconfigure the network effectively and efficiently becomes more important.

The fact that the equipment patch cords don’t have a dedicated termination location makes patch cord labeling and record keeping both more difficult and more critical. Interconnect generally works best in low fiber count (less than 144 fibers) systems in which the distance between the ODF and the equipment is short.

Conclusion

Interconnect can be more cost- efficient in initial installation, requiring a minimum amount of equipment and floor space. But the more a network changes, the more desirable a cross-connect architecture becomes.

To learn more about connectors and to understand the requirements for intra- and inter- linking buildings with fiber explore our Fiber Optic Infrastructure Specialist Training Certification Course.