How to specify a fiber patch cord
Six things define a fiber patch cord: the connector at each end, the polish, the fiber type, simplex or duplex, the length and the jacket.
Connectors at each end
- LC: the small connector used on SFP transceivers, duplex QSFP optics such as LR4, and high-density panels.
- SC: a larger push-pull connector, common on FTTH equipment, ODFs and older switches.
- FC: a screw-on metal connector, found on test equipment and some older telecom gear.
The two ends can differ, for example LC at the switch and SC at the panel.
Polish
Single-mode connectors are UPC (blue) or APC (green). Choose the polish of the port each end plugs into, and never mate APC with UPC. Multimode connectors are PC. UPC vs APC explains the difference.
Fiber type
OS2 is single-mode, for telecom, FTTH and long links. OM3 and OM4 are multimode, for short links in buildings and data centres. The transceivers decide: SR optics need multimode, LR optics need single-mode. See OS2 vs OM3 vs OM4.
Simplex or duplex
Most transceivers use two fibers, one to transmit and one to receive, so they need a duplex cord. Simplex cords carry one fiber. They are used in FTTH, where a PON runs both directions on one fiber, and with single-fiber BiDi optics.
Length
Length is measured from connector tip to connector tip. Measure along the route the cord will follow, through cable managers and trays, and add some slack.
Jacket
LSZH jackets give off little smoke and no halogen gases in a fire, so they are often specified indoors and in data centres. PVC is the general-purpose choice. Cords are usually 2.0 mm or 3.0 mm across; pigtails for splice trays have a 0.9 mm buffer.
Example order line
Put it all on one line with the quantity:
LC/UPC to SC/UPC duplex patch cord, OS2 single-mode, 3 m, LSZH jacket, 2.0 mm, 50 pcs
The patch cord builder writes this line for you as you choose the options.
Mistakes to avoid
- Mating an APC connector with a UPC one.
- Ordering multimode cords for single-mode optics, or the other way round.
- Ordering simplex when the transceiver needs duplex.
- Measuring the straight-line distance instead of the cable route.
Related
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List the items, one per line. Send drawings or photos on WhatsApp or to rudraopti@gmail.com.