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Understanding the splice tables

A row-by-row guide to the splice tables CSV from a Fiber Design project: splices, splits, express, spare and dead fibers, with worked examples.

This article explains how to read the splice tables CSV you export from a Fiber Design project. To export it, or to explore splicing interactively in the Splicing view, see Splice tables.

How the CSV is organized

The CSV has one row for each fiber at each closure (hub or splice point). For splitters, there’s one row for each splitter output. Rows are grouped by closure.

Column Contains
closure The hub or splice point where the fiber is handled
cable_in The incoming cable, or dead
fibre_in The fiber number on the incoming cable
tier_in The network tier of the incoming cable, for example FEEDER or DISTRIBUTION
type What happens to the fiber here: splice, split, express, spare or dead
cable_out The outgoing cable, or spare or dead
fibre_out The fiber number on the outgoing cable
tier_out The network tier of the outgoing cable

The examples below leave out the tier columns to keep them readable.

Example: a drop hub

Here are the splice tables for a drop hub fed by an 8-fiber distribution cable, serving three premises through 2-fiber drop cables:

closure cable_in fibre_in type cable_out fibre_out
DROP_HUB_0210 DIST_CABLE_0219 1 splice DROP_CABLE_3190 1
DROP_HUB_0210 DIST_CABLE_0219 2 splice DROP_CABLE_3191 1
DROP_HUB_0210 DIST_CABLE_0219 3 splice DROP_CABLE_3192 1
DROP_HUB_0210 DIST_CABLE_0219 4 spare spare  
DROP_HUB_0210 DIST_CABLE_0219 5 dead dead  
DROP_HUB_0210 DIST_CABLE_0219 6 dead dead  
DROP_HUB_0210 DIST_CABLE_0219 7 dead dead  
DROP_HUB_0210 DIST_CABLE_0219 8 dead dead  
DROP_HUB_0210 dead   dead DROP_CABLE_3190 2
DROP_HUB_0210 dead   dead DROP_CABLE_3191 2
DROP_HUB_0210 dead   dead DROP_CABLE_3192 2

Each type of row is explained below.

Splice

A splice row means a fiber on the incoming cable is spliced to a fiber on an outgoing cable. From the first three rows:

  • Fiber 1 of DIST_CABLE_0219 is spliced to fiber 1 of DROP_CABLE_3190.
  • Fiber 2 of DIST_CABLE_0219 is spliced to fiber 1 of DROP_CABLE_3191.
  • Fiber 3 of DIST_CABLE_0219 is spliced to fiber 1 of DROP_CABLE_3192.

Spare

A spare row means a lit fiber, one that traces back to the source, reaches this closure and is left spare there. There’s no outgoing cable or fiber.

In the example, fiber 4 of DIST_CABLE_0219 is left spare at the drop hub.

Dead: incoming

A dead row where cable_out is dead means a fiber on the incoming cable is dark: it has no connection back to the source.

In the example, fibers 5–8 of DIST_CABLE_0219 are dark.

Dead: outgoing

A dead row where cable_in is dead means a fiber on an outgoing cable isn’t connected to anything coming in. Designs don’t usually use every fiber in every cable.

In the example, each drop cable has two fibers but only needs one. So fiber 2 of each of DROP_CABLE_3190, 3191 and 3192 is unused.

Example: a distribution hub with splitters

Split

A split row means an incoming fiber goes into a splitter. There’s one row for each splitter output, so the same fibre_in appears several times.

Here are some rows from a distribution hub with 1:8 splitters:

closure cable_in fibre_in type cable_out fibre_out
DIST_HUB_0021 FEEDER_CABLE_0045 1 split DIST_CABLE_0197 1
DIST_HUB_0021 FEEDER_CABLE_0045 1 split DIST_CABLE_0197 2
… … … … … …
DIST_HUB_0021 FEEDER_CABLE_0045 1 split DIST_CABLE_0197 8
DIST_HUB_0021 FEEDER_CABLE_0045 2 split DIST_CABLE_0197 9
… … … … … …
DIST_HUB_0021 FEEDER_CABLE_0045 3 split DIST_CABLE_0197 21
DIST_HUB_0021 FEEDER_CABLE_0045 3 spare spare  
DIST_HUB_0021 FEEDER_CABLE_0045 3 spare spare  
DIST_HUB_0021 FEEDER_CABLE_0045 3 spare spare  
DIST_HUB_0021 FEEDER_CABLE_0045 4 splice FEEDER_CABLE_0046 4
… … … … … …
DIST_HUB_0021 dead   dead DIST_CABLE_0197 22

Reading these rows:

  • Fiber 1 of FEEDER_CABLE_0045 appears eight times. It goes through a 1:8 splitter and feeds fibers 1–8 of DIST_CABLE_0197. Fiber 2 feeds fibers 9–16 the same way.
  • Fiber 3 goes through a third splitter. Five of its outputs feed fibers 17–21, and the other three outputs are left spare.
  • Fibers 4 onwards aren’t split here. They’re spliced straight through to FEEDER_CABLE_0046 to serve hubs further along the network.
  • Fibers 22–24 of DIST_CABLE_0197 aren’t used.

Example: express fibers at a splice

Express

An express row means a fiber passes through the closure uncut: it continues on the same physical cable with the same fiber number. Express fibers keep a trunk running through, while only the fibers needed for a branch (lateral) are cut and spliced.

Fibers can usually stay uncut when the incoming and outgoing cables are in the same tier and are the same size.

closure cable_in fibre_in type cable_out fibre_out
DIST_SPLICE_0004 DIST_CABLE_0004 1 splice DIST_CABLE_0006 1
DIST_SPLICE_0004 DIST_CABLE_0004 2 express DIST_CABLE_0005 2
DIST_SPLICE_0004 DIST_CABLE_0004 3 express DIST_CABLE_0005 3
… … … … … …
DIST_SPLICE_0004 DIST_CABLE_0004 6 express DIST_CABLE_0005 6

Here, fibers 2–6 run uncut from DIST_CABLE_0004 into DIST_CABLE_0005 as a trunk. Fiber 1 is cut and spliced into the branch cable, DIST_CABLE_0006.

To encourage more express fibers in your designs, turn off Taper cables in your distribution tier settings. See Distribution tier settings.

Express isn’t the same as bypassing a splitter. In fiber networks, “express fiber” sometimes means a fiber that bypasses a splitter to give a location an unsplit fiber. In the splice tables, express only means a fiber passes through a closure uncut.

Cable IDs that aren’t on the map

Some cable IDs in the CSV don’t appear on the map:

  • <HUB_ID>-<SERVICE_LOCATION_ID>: a dedicated fiber from a hub to a single premises