A fibre optic patch cord is a short length of fibre cable with a connector at each end, used to connect equipment to a panel or one panel to another. Radix Fibrotech makes LC, SC, FC and ST patch cords, simplex or duplex, in single-mode and multimode, with UPC or APC end faces, cut to the length on the order.
What a fibre optic patch cord is
A fibre optic patch cord, or fiber optic patch cord in US usage, is a factory-terminated fibre cable with a connector at each end. It links a transceiver to a patch panel, a panel to another panel, or test equipment to a link. Because it is handled more than any other part of the network, the patch cord is where most connector damage and contamination happen.
Four choices define a patch cord: the connector at each end, simplex or duplex, the fibre type, and the end-face polish. Get those right and the cord will mate; get one wrong and it will not, or it will mate and carry excess loss.
The most ordered pairings have their own pages with configuration tables: LC to LC patch cords, SC to SC patch cords and LC to SC patch cords.
Connector types
| Connector | Ferrule | Coupling | Where it is used |
|---|---|---|---|
| LC | 1.25 mm | Push-pull latch | SFP and QSFP transceivers, high-density panels, data centres |
| SC | 2.5 mm | Push-pull, square body | Enterprise panels, access networks, older equipment |
| FC | 2.5 mm | Threaded | Test equipment, vibrating machinery, instruments |
| ST | 2.5 mm | Bayonet | Legacy multimode, industrial and campus installations |
A cord can have a different connector at each end, for example LC to SC, to join new equipment to an existing panel. The fibre connector types guide covers these and the specialist connectors. Multi-fibre MPO cords are a separate family, covered under MPO patch cords.
Simplex and duplex
A simplex cord carries one fibre. A duplex cord carries two, one for each direction, joined side by side as a zip cord or in a single round jacket, with the connectors held together by a duplex clip. Most network links are duplex. Simplex cords suit single-fibre bidirectional optics, test leads and some sensing systems.
Duplex cords must arrive with the polarity the channel expects: transmit at one end connected to receive at the other. On LC duplex cords this is the A-to-B arrangement, and a cord delivered A-to-A will need its clip reversed or replacing.
Single-mode and multimode
| Fibre | Core/cladding | Usual jacket colour | Typical use |
|---|---|---|---|
| OS2 | 9/125 µm | Yellow | Long links, access networks, single-mode optics |
| OM1 | 62.5/125 µm | Orange | Legacy multimode equipment |
| OM2 | 50/125 µm | Orange | Legacy multimode equipment |
| OM3 and OM4 | 50/125 µm | Aqua (OM4 sometimes violet) | 10G to 100G short-reach links |
| OM5 | 50/125 µm | Lime green | Shortwave wavelength-division links |
A patch cord must match the fibre in the link it joins. Mixing 62.5 µm and 50 µm multimode, or connecting multimode to single-mode, causes large losses. The single-mode versus multimode guide explains the difference.
UPC and APC end faces
UPC connectors are polished with a slight dome and are the default for most single-mode data links. APC connectors are polished at 8 degrees so reflected light leaves the core; they are used in RF video, passive optical networks and other systems sensitive to back reflection. APC single-mode connectors are normally green, UPC single-mode connectors blue.
An APC connector must never be mated with a UPC connector. The two end faces meet with an air gap, the loss is high, and both end faces can be damaged.
What drives fibre patch cord price
Buyers comparing fibre patch cord prices usually find wide ranges. The differences come from the following:
- Connector type and count. A duplex cord has four connectors to terminate and test; MPO and ruggedised connectors cost more than LC or SC.
- Polish. APC polishing and inspection take more process time than UPC.
- Fibre grade. OM4 and OM5 fibre cost more than OM3 and OS2 per metre.
- Loss grade. A tighter maximum insertion loss narrows the acceptable parts.
- Jacket. LSZH, plenum, armoured and tactical jackets each change the cable cost.
- Length. Fibre is a small share of a short cord and a large share of a long one.
- Test data and labelling. Per-cord reports, serial labels and custom marking add handling.
- Quantity per configuration. Many identical cords cost less each than many different ones.
Comparing quotes is only fair when the specifications match on every one of these points.
Testing, inspection and care
Radix measures insertion loss and return loss on each channel and supplies the report with the order. Keep the reports: they are the baseline if a link later shows high loss.
Most patch cord failures in service are contamination. A single dust particle on a single-mode core can block a large part of the signal. Inspect each end face with a fibre microscope before mating, clean it if needed, and inspect again. Keep dust caps on unmated connectors. Do not bend cords tighter than their rated minimum bend radius, and do not hang cord weight from the connector; support the cable in the frame's management.
Ordering patch cords
For each line give the connector and polish at each end, simplex or duplex, fibre type, jacket and diameter, length, labels and quantity. For floors and machine runs where a standard cord would be crushed, consider LC, FC, SC and ST duplex armoured tactical cable. Send the list through the request a quote page.
Questions buyers ask
Which patch cord do I need for an SFP transceiver?
Most SFP and SFP+ transceivers use an LC duplex port. Match the fibre type to the optic: single-mode optics need OS2, short-reach multimode optics need OM3 or OM4. The transceiver datasheet states both.
Can I connect an APC patch cord to a UPC port?
No. The angled and domed end faces leave an air gap, which causes high loss and can damage both connectors. APC connectors are usually green and UPC single-mode connectors blue, which helps avoid mistakes.
Is OM3 or OM4 patch cord compatible with OM2?
They share the 50 µm core size and will mate, but the channel performs only to the lowest grade in it. Mixing 50 µm with 62.5 µm OM1 causes significant loss and should be avoided.
Why do fibre patch cord prices vary so much?
Price depends on connector type, polish, fibre grade, loss grade, jacket, length, test data and quantity. Two cords that look alike can differ on several of these, so compare full specifications.
Can you make patch cords in custom lengths?
Yes. Lengths are cut to the order rather than taken from a fixed list. State the tolerance if the length is critical.