An LC to LC patch cord is a fibre cable with a 1.25 mm LC connector at each end, used to link SFP, SFP28 and QSFP28 duplex ports to patch panels, cassettes and other switches. It comes in OS2 single-mode or OM3, OM4 and OM5 multimode, simplex or duplex, with UPC or APC polish. Radix Fibrotech makes them to order in Pune and tests each cord.
LC to LC patch cord options
An LC to LC patch cord has a small-form LC connector with a 1.25 mm ferrule at both ends and is the standard cord for SFP-family transceiver ports and high-density LC panels. Radix makes each cord to order in Pune from the options below, so one order line can combine any fibre, polish, jacket and length. The LC connector guide covers the connector itself.
| Option | Choices | Notes |
|---|---|---|
| Fibre type | OS2 9/125 µm single-mode; OM3, OM4 or OM5 50/125 µm multimode | Jacket usually yellow for OS2, aqua for OM3 and OM4 (OM4 sometimes violet), lime green for OM5 |
| Fibre count | Simplex or duplex | Duplex for almost all transceiver links; simplex for single-fibre bidirectional optics and test leads |
| End face | UPC or APC, chosen for each end | APC is a single-mode option; multimode LC connectors are PC or UPC polished |
| Duplex style | Standard duplex clip or uniboot | A uniboot carries both fibres in one round jacket with a single boot |
| Jacket | LSZH, PVC, riser (OFNR) or plenum (OFNP), armoured | Riser and plenum are US National Electrical Code ratings; LSZH where the site specifies low smoke |
| Diameter | 1.6, 2.0 or 3.0 mm duplex zip; round uniboot jacket | Smaller cords ease routing and airflow in full racks |
| Length | Any length to order | State a tolerance if the route is tight |
Where LC to LC cords are used
In data centres and equipment rooms, LC to LC cords make most of the short duplex connections:
- Switch port to patch panel or cassette. An SFP+, SFP28 or QSFP28 duplex optic patches to an LC panel, or to the LC front of an MPO cassette that carries the link onward on a trunk.
- Server to top-of-rack switch. A short duplex cord runs from the server network card to the switch in the same rack.
- Switch to switch. Cords join leaf and spine switches through panels at each end of a row.
- Test and monitoring. Duplex cords connect optical taps and test sets to live panels.
The cord must match the fibre type the optic was designed for. Common duplex LC optics:
| Optic | Fibre | Published channel reach |
|---|---|---|
| 10GBASE-SR | OM3 or OM4 | 300 m on OM3, 400 m on OM4 |
| 25GBASE-SR | OM3 or OM4 | 70 m on OM3, 100 m on OM4 |
| 10GBASE-LR and 25GBASE-LR | OS2 | 10 km |
| 100GBASE-LR4 | OS2 | 10 km |
| 100G CWDM4 (multi-source agreement) | OS2 | 2 km |
These reaches come from IEEE 802.3 or the relevant multi-source agreement and apply to the whole channel, not to one cord. OM5 earns its place with shortwave wavelength-division optics; for the optics above, OM4 cords are the usual match. The OM3 vs OM4 vs OM5 guide explains the grade choice.
Duplex polarity: A-to-B, A-to-A and reversing a uniboot
Each LC duplex connector has two positions, A and B. In an A-to-B cord the fibre in position A at one end lands in position B at the other, so transmit at one device reaches receive at the other. This crossed cord is the default duplex patch cord in TIA-568 cabling, and it is what Radix supplies unless the order says otherwise.
An A-to-A cord keeps each fibre in the same position at both ends. It is used where the crossover is made elsewhere in the channel, for example in some MPO trunk and cassette polarity methods; the MPO polarity guide shows how the methods combine. With the wrong cord the link simply does not come up. Nothing is damaged.
On a standard duplex cord, polarity is changed by opening the clip, swapping the two connectors and closing it again. On a uniboot cord the two connectors sit in one housing; depending on the design, the latch is rotated to the other side or the connector bodies are swapped within the housing, with no re-termination. Follow the maker's method, then correct the A and B labels so the markings still match the wiring.
Bend-insensitive fibre for dense racks
A full switch can carry dozens of LC cords bent around cable managers and door edges. Standard single-mode fibre to ITU-T G.652.D loses light at tight bends. Bend-insensitive single-mode fibre to ITU-T G.657.A1 or G.657.A2 tolerates much smaller bend radii and is compatible with G.652.D, so it can be mixed into an existing plant. Bend-insensitive multimode fibre does the same job for OM3, OM4 and OM5 cords.
Bend-insensitive fibre reduces loss at bends. It does not protect a crushed or kinked cord. Keep to the cable's stated minimum bend radius and route cords through the manager rather than letting them hang from the port. Ask for bend-insensitive fibre on the quote, since it is not assumed.
Testing and labelling each cord
Radix tests every LC to LC cord before it is packed. The usual factory checks are insertion loss on each fibre, return loss on single-mode connectors and end-face inspection against IEC 61300-3-35 criteria. Single-mode cords are measured at 1310 and 1550 nm, multimode cords at 850 nm and often 1300 nm. State the maximum insertion loss per connector you need and the report format in the quote; the report becomes the baseline for later fault finding.
For reference, TIA-568 allows up to 0.75 dB per mated connector pair in channel planning, and return loss of 50 dB or better for UPC and 60 dB or better for APC are widely used industry figures. Factory-made cords normally sit well inside the planning allowance, which is why a per-cord figure is worth asking for.
Labels keep a dense rack maintainable. A unique cord number on heat-shrink or flag labels at both ends, with A and B position markings and the far-end port reference, lets a technician trace a cord without pulling it. Schemes based on the TIA-606 administration standard are common in data centres. Give the label text format on the order.
What to put in an LC to LC quote
Give one line per configuration, with:
- fibre type, and bend-insensitive fibre if wanted
- simplex or duplex, and standard clip or uniboot
- UPC or APC at each end
- polarity (A-to-B unless stated)
- jacket rating and outer diameter
- length and tolerance
- label text and test report format
- quantity for that line
Send the list through the request a quote page. Other connector pairs and cord families are on the fibre optic patch cords page.
What changes the price of an LC to LC cord
Radix prices LC to LC cords on request, against the specification. The factors that move the figure are these:
- Uniboot housing. It costs more than a standard clip and needs round duplex cable.
- Fibre grade. OM5 and bend-insensitive fibres cost more per metre than OM3 or standard OS2.
- APC ends. Angled polishing adds process time.
- Jacket rating. Plenum and armoured jackets cost more than LSZH or PVC.
- Loss grade and reports. A tighter maximum and serialised test data add inspection and handling.
- Line count. Many cords of one configuration cost less each than a mix of small lines.
Questions buyers ask
Is an LC to LC duplex patch cord crossed over?
Yes, by default. A standard duplex cord is wired A-to-B, so the transmit fibre at one end becomes the receive fibre at the other. A-to-A cords are made on request for channel designs that cross over elsewhere.
What is the difference between a uniboot and a standard LC duplex cord?
A standard duplex cord is two simplex legs held by a clip, usually on zip cable. A uniboot puts both fibres in one round jacket with a single boot, which takes less space at the switch and lets polarity be reversed without tools. Uniboot cords cost more.
Do I need APC LC cords in a data centre?
Usually not. Most duplex LC optics in data centres expect UPC single-mode or PC multimode connectors. APC LC cords are used where back reflection matters, such as RF video and some passive optical network equipment. Check the port before ordering.
How long should an LC to LC cord be for a rack?
Measure the route through the cable managers, not the straight distance between ports, and add a small allowance for slack. Cords that are far too long end up coiled in the manager and block airflow. Order to the measured route rather than rounding up to a stock size.
Is a fiber optic jumper the same as an LC to LC patch cord?
Jumper and patch cord mean the same thing: a short cable with a connector at each end. An LC to LC jumper is one type, with LC connectors at both ends. The word jumper is more common in US and telecom usage.