DCD Design Note 126.0

FCC Fibrmax System:

Integrating Legacy Fiber Cables

Darryl Wohlt

December 1, 1997

As the Fibrmax fiber distribution system continues to develop in FCC, it is our intention to migrate the legacy interbuilding and intrabuilding (FCC) fiber cable terminations to the Fibrmax, and eliminate the existing "fiber closet" racks and panels. Table 1 lists the cables to be migrated from the fiber closet racks.

Some of the interbuilding fiber cables (e.g., from PS1, CHL, EAD, etc.) enter the "fiber closet" racks FRR27 and FRR28 from under the floor, with enough service slack to enable us to reroute them directly through a Fibrmax tube distribution unit (TDU) into their assigned Fibrmax connector cards without additional splicing, if we choose to do so.

Other interbuilding cables (e.g., the new runs from CDF and ICB) were pulled to FRR27 via the wall penetration, and there is not enough slack to re-route them under the floor to a TDU. The intrabuilding cables from panels elsewhere in the FCC also have insufficient slack to reach their assigned Fibrmax cards. In these cases, splicing will be necessary.

Since 16 of the 21 cables listed in Table 1 will need to be spliced, it may be more practical to simply splice all of them (except for those from FRR19 and FRR29, which will be replaced). There are three potential locations for a splice enclosure: a) the wall behind the existing fiber racks, b) the empty vertical cable ladder behind the junction box in the electrical closet, and c) under the floor in the FRR27/28 area.

The floor under the fiber racks is congested and would pose difficulties during splicing and final positioning of the enclosure if Option C is chosen. Option B would hide most of the cabling and hardware (except for a new wall penetration near the floor) and provide a moderately accessible work area for splicing. Option A would leave cabling components in plain sight on the wall, which may be undesirable, but may be the easiest to implement. This design assumes we will use Option A (Figure 1).

We will use a standard indoor splice enclosure wall-mounted near the penetration to the electrical closet. This enclosure will be a Siecor OSE-HD model initially containing 12 splice trays, resulting in a fiber capacity of 432 strands. The OSE-HD can house up to twenty-four 36-splice OSE-ST-2 trays. Working inside this cabinet will be impossible with FRR27 directly in front of it, but the racks can be moved forward enough to allow access and work space.

The FCC Fibrmax system model described in a previous design note requires that all ports of a network device (e.g., router, switch, concentrator) are to be patched to the Fibrmax, so that all jumper connections are made within the Fibrmax and not at the equipment. This method is probably better suited for devices having large port counts, preferably in multiples of 12. It will be awkward for the most part to retrofit this scheme into the FCC2E equipment racks, which contain a wide variety of devices with port counts ranging from 2 to 32, and still maintain a semblance of organization and flexibility. Many of the fanout cables in the concentrator rack (FRR20), for example, would have unconnected pigtails because of the different concentrator port capacities. Therefore, this design note preserves the current arrangement using patch panels in the equipment racks, but it calls for the installation of higher density panels and new cables to replace the existing ones.

Fibrmax 2720/2725 connector cards (Table 2) will be positioned inside the Fibrmax housings. Cards will be needed in the "Interbuilding" housing to accept all multimode and singlemode strands coming in from each interbuilding fiber cable. Cards will also be needed in the FCC "nth Floor" housings to receive strands from FCC fiber panels (except those in the FCC2E Datacom area).

Current connections on the legacy panels will be surveyed, and patching between Fibrmax cards will be done ahead of time based upon the survey. A log sheet will be maintained nearby, to document patch changes made after the survey.

New 12-slot, 72-port Siemon RIC ST/SC adapter cabinets will be placed under the existing Siecor cabinets in FRR19 and FRR29. 12-strand SC fanout cables will be run from these cabinets to connector cards in Fibrmax Rack 1 Housing 1. The reason for using front-facing ST connectors rather than SC’s in the panels, is cost. We would otherwise need to replace more than 24 ST-MIC jumpers with SC-MIC jumpers in this area.

In any case, as the network equipment evolves, we will have the option of connecting the SC-tipped fanouts directly to equipment ports, or replace the ST/SC panels with SC/SC versions and use SC jumpers. It’s also conceivable that we will want greater mobility for these cables, to reach other racks in the datacomm area. For this reason, we will use longer than usual fanout cables. A 65-foot fanout cable will reach the south end of the rack line (e.g., the old port selector cabinets) from the topmost Fibrmax Rack 1 housing, using the underfloor cable troughs.

Another 72-port Siemon RIC ST/SC panel will be installed in FRR2 to provide connectivity for the odd devices in that cluster of racks. This panel will also be attached to Fibrmax with 12-strand SC fanout cables.

The splice enclosure and related hardware will be installed, and riser-rated fiber cables will be run from the splices to the designated Fibrmax cards, as described below.

The Fibrmax Tube Distribution Units (TDUs) can easily accommodate conventional fiber cable as well as air-blown fiber (ABF). See Figure 2.

We will use conventional riser-rated high capacity tight-buffered fiber cables (e.g., Siecor Unitized MICâ ) between the splice enclosure and the Fibrmax system. Five 72-strand multimode cables and one 48-strand single mode cable will be required.

The fiber cables from the splice enclosure will be brought in through the TDU bottom panel and secured with a collar or bushing. The outer jacket will be removed just above the collar, exposing multiple bundles containing six 900-micron fiber strands each. (Note: Figure 2’s notation about sealant applies only to gel-filled cables.) The bundle tubes will be routed up into the rack in the same manner as the ABF bundles, and stripped just before the connector card feed tubes. The individual 900-micron strands will continue on, looped inside the card, and inserted into the Fibrlok splices. The Fibrloks will not be clamped down until a jumper strand has been inserted (some of them will not receive a jumper at this time).

During a scheduled outage(s), the legacy fiber cables will be cut from their panel connectors or breakout kits, maintaining as much remaining length as possible, and re-routed to the Siecor OSE-HD. Cables running under the floor will be brought up through the OSE’s bottom panel, and the cables emerging through the wall penetration will enter the OSE through its top panel. Cables will be fusion-spliced to the risers. Service loops will be preserved in the closet junction box or under the floor, as applicable. Figure 3 shows the orientation of the incoming cables and risers, and how the OSE splice trays may be allocated.

It is not likely that the entire set of fiber cables from all locations can be moved to the Fibrmax at one time, and multiple outages may need to be arranged. Since we will have a subcontractor perform the splicing, the subcontract may have to be worded to arrange multiple visits, or separate subcontracts may need to be written.

It is estimated that each cable would take about an hour to cut from its old panel and redress it into the Siecor enclosure. Depending upon the equipment used for fusion splicing and the technician’s skill, each 12 splices should take 30-45 minutes to complete. Fermilab personnel would handle jumper cutovers at the network equipment, which should take only a few minutes (since Fibrmax jumpers would be pre-installed) and would be done after the subcontractor has completed the splices related to those connections. Table 3 illustrates estimated outage times for each cable. FRR29 and FRR19 cables will be replaced, not spliced, which will save some time.

Outage

Except for cables from the FRR19 and FRR29 panels, all interbuilding and intrabuilding fiber cables in fiber closet racks FRR27 and FRR28 will be spliced at an intermediate enclosure before entering the Fibrmax system. The splice enclosure and related Fibrmax connector cards will be pre-cabled with high capacity riser cables. The FRR19 and FRR29 panels will be supplanted with new ones, which would also be pre-cabled. All Fibrmax cards would be pre-jumpered.

We will follow the FCC Fibrmax system model, which specifies that Rack 2 housings will be filled up first, before expanding horizontally to Rack 3. Housings 1-3 are assigned to FCC floors 1-3, Housing 4 is allocated to interbuilding cables. Rack 1 is for network electronics, and the new FRR19/29 panels will be attached to that housing.

With the splice enclosure in place, we will arrange outages as appropriate to cut the cables over to Fibrmax. Splicing will be done by a subcontractor.

Description Total Cost

Siecor OSE Splice Enclosure & Hardware $1,995.00

Riser Cable (incl. fanouts) $5,999.00

Siemon Fiber Panels $2,271.00

Fibrmax Components $9,562.00

Miscellaneous Hardware $1,000.00

Labor to cut, redress and splice all cables $8,840.00

Contingency (10%) $2,967.00